Bismuth (83Bi) has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as 208.98040(1). Although bismuth-209 is now known to be unstable, it has classically been considered to be a "stable" isotope because it has a half-life of over 1.9×1019 years, which is more than a billion (1000 million) times the age of the universe.

Isotope lists, 97+ if you want a list with just one giant list of isotopes, see Isotope lists, all.

Naturally occurring niobium (41Nb), element 41, is composed of one stable isotope (93Nb). 93Nb is the lightest nuclide theoretically susceptible to spontaneous fission, and although this has never been observed, it makes niobium theoretically the lightest element with no stable isotope. The first 40 elements (to zirconium) all have at least one stable nuclide susceptible in theory only to proton decay.The most stable radioisotope is 92Nb with a half-life of 34.7 million years.

There are 37 known isotopes of iodine (53I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element.Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide. Cosmogenic sources of 129I produce very tiny quantities of it that are too small to affect atomic weight measurements; iodine is thus also a mononuclidic element—one that is found in nature only as a single nuclide. Most 129I derived radioactivity on Earth is man-made, an unwanted long-lived byproduct of early nuclear tests and nuclear fission accidents.All other iodine radioisotopes have half-lives less than 60 days, and four of these are used as tracers and therapeutic agents in medicine. These are 123I, 124I, 125I, and 131I. All industrial production of radioactive iodine isotopes involves these four useful radionuclides.The isotope 135I has a half-life less than seven hours, which is too short to be used in biology. Unavoidable in situ production of this isotope is important in nuclear reactor control, as it decays to 135Xe, the most powerful known neutron absorber, and the nuclide responsible for the so-called iodine pit phenomenon.In addition to commercial production, 131I (half-life 8 days) is one of the common radioactive fission-products of nuclear fission, and is thus produced inadvertently in very large amounts inside nuclear reactors. Due to its volatility, short half-life, and high abundance in fission products, 131I, (along with the short-lived iodine isotope 132I from the longer-lived 132Te with a half-life of 3 days) is responsible for the largest part of radioactive contamination during the first week after accidental environmental contamination from the radioactive waste from a nuclear power plant.The relative atomic mass of iodine is 126.90447(3).

There are 33 known isotopes of krypton (36Kr) with atomic mass numbers from 69 through 101. Naturally occurring krypton is made of six stable isotopes, two of which might theoretically be slightly radioactive, plus traces of radioisotopes that are produced by cosmic rays in the atmosphere.The spectral signature of krypton can be observed to have several very sharp lines. When krypton is placed into an electric discharge tube, it emits visible light with a distinctive orange-red color.

Naturally occurring manganese (25Mn) is composed of 1 stable isotope, 55Mn. 25 radioisotopes have been characterized with the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the remaining radioactive isotopes have half-lives that are less than 3 hours and the majority of these have half-lives that are less than 1 minute, but only 45Mn has an unknown half-life. The least stable is 44Mn with a half-life shorter than 105 nanoseconds. This element also has 3 meta states.Manganese is part of the iron group of elements, which are thought to be synthesized in large stars shortly before supernova explosion. 53Mn decays to 53Cr with a half-life of 3.7 million years. Because of its relatively short half-life, 53Mn occurs only in tiny amounts due to the action of cosmic rays on iron in rocks. Manganese isotopic contents are typically combined with chromium isotopic contents and have found application in isotope geology and radiometric dating. Mn−Cr isotopic ratios reinforce the evidence from 26Al and 107Pd for the early history of the solar system. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate an initial 53Mn/55Mn ratio that suggests Mn−Cr isotopic systematics must result from in-situ decay of 53Mn in differentiated planetary bodies. Hence 53Mn provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.The isotopes of manganese range in atomic weight from 46 u (46Mn) to 65 u (65Mn). The primary decay mode before the most abundant stable isotope, 55Mn, is electron capture and the primary mode after is beta decay.

Natural hafnium (72Hf) consists of five stable isotopes (176Hf, 177Hf, 178Hf, 179Hf, and 180Hf) and one very long-lived radioisotope, 174Hf, with a half-life of 2×1015 years. In addition, there are 30 other known radionuclides, the most stable of which is 182Hf with a half-life of 8.9×106 years. No other radioisotope has a half-life over 1.87 days. Most isotopes have half-lives under 1 minute.

Isotope lists, 25-48 if you want a list with just one giant list of isotopes, see Isotope lists, all.

Francium (87Fr) has no stable isotopes. A standard atomic weight cannot be given. Its most stable isotope is 223Fr with a half-life of 22 minutes, occurring in trace quantities as an intermediate decay product of 235U. The other natural isotope is 221Fr.Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable. All elements with atomic number of greater than or equal to 106 (seaborgium) have most-stable-known isotopes shorter than that of francium, but those elements have only a relatively small number of isotopes discovered, thus, there is the possibility of a yet-unknown isotope having a longer half-life.

Naturally occurring barium (56Ba) is a mix of six stable isotopes and one very long-lived radioactive primordial isotope, barium-130, recently identified as being unstable by geochemical means (from analysis of the presence of its daughter xenon-130 in rocks).

Arsenic (33As) has 33 known isotopes and at least 10 isomers. Only one of these isotopes, 75As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73As has a half-life of 80 days. Arsenic has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material).

Lead (82Pb) has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively. These series represent the decay chain products of long-lived primordial U-238, U-235, and Th-232, respectively. However, each of them also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium. (See lead-lead dating and uranium-lead dating).The longest-lived radioisotopes are 205Pb with a half-life of ≈15.3 million years and 202Pb with a half-life of ≈53,000 years. Of naturally occurring radioisotopes, the shortest half-life is 22.20 years for 210Pb, which is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years.The relative abundances of the four stable isotopes are approximately 1.5%, 24%, 22%, and 52.5%, combining to give a relative atomic mass (abundance-weighted average of the stable isotopes) of 207.2(1). Lead is the element with the heaviest stable isotope, 208Pb. (The more massive 209Bi, long considered to be stable, actually has a half-life of 1.9×1019 years). A total of 38 Pb isotopes are now known, including very unstable synthetic species.In its fully ionized state the isotope 205Pb also becomes stable.

Potassium (19K) has 24 known isotopes from 32K to 56K. Three isotopes occur naturally: stable 39K (93.3%) and 41K (6.7%), and the long-lived radioisotope 40K (0.012%).Naturally occurring radioactive 40K decays to stable 40Ar (10.72% of decays) by electron capture or positron emission (giving it the longest known positron-emitter nuclide half-life). Alternately, and most of the time (89.28%), it decays to stable 40Ca by beta decay. 40K has a half-life of 1.248×109 years.

Natural platinum (78Pt) occurs in five stable isotopes (192Pt, 194Pt, 195Pt, 196Pt, 198Pt) and one very long-lived (half-life 6.50×1011 years) radioisotope (190Pt). There are also 31 known artificial radioisotopes, the longest-lived of which is 193Pt with a half-life of 50 years. All other isotopes have half-lives under a year, most under a day.

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Chlorine (17Cl) has 24 isotopes with mass numbers ranging from 28Cl to 51Cl and 2 isomers (34mCl and 38mCl). There are two principal stable isotopes, 35Cl (75.78%) and 37Cl (24.22%), giving chlorine a standard atomic weight of 35.45. The longest-lived radioactive isotope is 36Cl, which has a half-life of 301,000 years. All other isotopes have half-lives under 1 hour, many less than one second. The shortest-lived are 29Cl and 30Cl, with half-lives less than 20 and 30 nanoseconds, respectively—the half-life of 28Cl is unknown.

Seaborgium (106Sg) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 263mSg in 1974. There are 12 known radioisotopes from 258Sg to 271Sg and 2 known isomers (261mSg and 263mSg). The longest-lived isotope is 269Sg with a half-life of 3.1 minutes.

Isothecium myosuroides, commonly known as slender mouse-tail moss or tree moss, is a true moss that grows abundantly on both rocks and trees. It is native to Eastern North America. It grows preferentially on angiosperms rather than on conifers because of the manner in which the former take in water creating an ideal moist habitat for the moss to grow on, and because many trees in the flowering plant families are less acidic than coniferous species of trees. Isothecium myosuroides also can grow on rocks.

Actinium (89Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 31 known isotopes, from 206Ac to 236Ac, and 2 isomers. Two isotopes are found in nature, 227Ac and 228Ac, as intermediate decay products of, respectively, 235U and 232Th. 228Ac is extremely rare, and almost all natural actinium is 227Ac.The most stable isotopes are 227Ac with a half-life of 21.772 years, 225Ac with a half-life of 10.0 days, and 226Ac with a half-life of 29.37 hours. All other isotopes have half-lives under 10 hours, and most under a minute. The shortest-lived known isotope is 217Ac with a half-life of 69 ns. Actinium also has two meta states.Purified 227Ac comes into equilibrium with its decay products (227Th and 223Fr) after 185 days.

Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over 3.1×1022 years), 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe. There are 24 known radioactive isotopes and their half-lives are shown below. See Brookhaven National Laboratory Interactive Table of Nuclides for a more accurate reading.Much of the past work on measuring the isotopic composition of Fe has centered on determining 60Fe variations due to processes accompanying nucleosynthesis (i.e., meteorite studies) and ore formation. In the last decade however, advances in mass spectrometry technology have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron. Much of this work has been driven by the Earth and planetary science communities, although applications to biological and industrial systems are beginning to emerge.

Protactinium (91Pa) has no stable isotopes. There are three naturally occurring isotopes, allowing a standard mass to be given.Twenty-nine radioisotopes of protactinium have been characterized, with the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 26.967 days, and 230Pa with a half-life of 17.4 days.

Nihonium (113Nh) is a synthetic element. Being synthetic, a standard atomic weight cannot be given and like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 284Nh as a decay product of 288Mc in 2003. The first isotope to be directly synthesized was 278Nh in 2004. There are 6 known radioisotopes from 278Nh to 286Nh, along with the unconfirmed 290Nh. The longest-lived isotope is 286Nh with a half-life of 19.6 seconds.

Carbon (6C) has 15 known isotopes, from 8C to 22C, of which 12C and 13C are stable. The longest-lived radioisotope is 14C, with a half-life of 5,700 years. This is also the only carbon radioisotope found in nature—trace quantities are formed cosmogenically by the reaction 14N + 1n → 14C + 1H. The most stable artificial radioisotope is 11C, which has a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is 8C, with a half-life of 2.0 x 10−21 s.

Gold (79Au) has one stable isotope, 197Au, and 18 radioisotopes, with 195Au being the most stable with a half-life of 186 days. Gold is currently considered the heaviest monoisotopic element (bismuth formerly held that distinction, but bismuth-209 has been found to be slightly radioactive).

Caesium (55Cs) or cesium as it is spelled in the United States has 40 known isotopes, making it, along with barium and mercury, the element with the most isotopes. The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years.

Livermorium (116Lv) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 293Lv in 2000. There are four known radioisotopes from 290Lv to 293Lv. The longest-lived isotope is 293Lv with a half-life of 53 ms.

Technetium (43Tc) is the first of the two elements lighter than bismuth that have no non-radioactive isotopes; the other such element is promethium. It is primarily artificial, only trace quantities existing in nature produced by spontaneous fission or neutron capture by molybdenum. The first isotopes to be synthesized were 97Tc and 99Tc in 1936, the first artificial element to be produced. The most stable radioisotopes are 98Tc (half-life of 4.2 million years), 97Tc (half-life: 2.6 million years) and 99Tc (half-life: 211,100 years).Thirty-three other radioisotopes have been characterized with atomic masses ranging from 85Tc to 120Tc. Most of these have half-lives that are less than an hour; the exceptions are 93Tc (half-life: 2.75 hours), 94Tc (half-life: 4.883 hours), 95Tc (half-life: 20 hours), and 96Tc (half-life: 4.28 days).Technetium also has numerous meta states. 97mTc is the most stable, with a half-life of 90.1 days (0.097 MeV). This is followed by 95mTc (half-life: 61 days, 0.038 MeV), and 99mTc (half-life: 6.04 hours, 0.143 MeV). 99mTc only emits gamma rays, subsequently decaying to 99Tc.For isotopes lighter than the most stable isotope, 98Tc, the primary decay mode is electron capture, giving molybdenum. For the heavier isotopes, the primary mode is beta emission, giving ruthenium, with the exception that 100Tc can decay both by beta emission and electron capture.Technetium-99 is the most common and most readily available isotope, as it is a major fission product from fission of actinides like uranium and plutonium with a fission product yield of 6% or more, and in fact the most significant long-lived fission product. Lighter isotopes of technetium are almost never produced in fission because the initial fission products normally have a higher neutron/proton ratio than is stable for their mass range, and therefore undergo beta decay until reaching the ultimate product. Beta decay of fission products of mass 95-98 stops at the stable isotopes of molybdenum of those masses and does not reach technetium. For mass 100 and greater, the technetium isotopes of those masses are very short-lived and quickly beta decay to isotopes of ruthenium. Therefore, the technetium in spent nuclear fuel is practically all 99Tc.One gram of 99Tc produces 6.2×108 disintegrations a second (that is, 0.62 GBq/g).Technetium has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given.

Isotope lists, 49-72 if you want a list with just one giant list of isotopes, see Isotope lists, all.

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Polonium (84Po) has 33 isotopes, all of which are radioactive, with between 186 and 227 nucleons. 210Po with a half-life of 138.376 days has the longest half-life of naturally occurring polonium. 209Po with a half-life of 125 years has the longest half-life of all isotopes of polonium. 209Po and 208Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron.

Roentgenium (111Rg) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 272Rg in 1994, which is also the only directly synthesized isotope, all others are decay products of nihonium, moscovium, and tennessine. There are 7 known radioisotopes from 272Rg to 282Rg.

Germanium (32Ge) has five naturally Elijah Jeffersonisotopes, 70Ge, 72Ge, 73Ge, 74Ge, and 76Ge. Of these, 76Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 1021 years (130 billion times the age of the universe).Stable 74Ge is the most common isotope, having a natural abundance of approximately 36%. 76Ge is the least common with a natural abundance of approximately 7%. When bombarded with alpha particles, the isotopes 72Ge and 76Ge will generate stable 75As and 77Se, releasing high energy electrons in the process.At least 27 radioisotopes have also been synthesized ranging in atomic mass from 58 to 89. The most stable of these is 68Ge, decaying by electron capture with a half-life of 270.95 d. It decays to the medically useful positron-emitting isotope 68Ga. (See gallium-68 generator for notes on the source of this isotope, and its medical use). The least stable known germanium isotope is 60Ge with a half-life of 30 ms.While most of germanium's radioisotopes decay by beta decay, 61Ge and 64Ge decay by β+ delayed proton emission. 84Ge through 87Ge also have minor β− delayed neutron emission decay paths.

Naturally occurring xenon (54Xe) is made of eight stable isotopes and one very long-lived isotope. (124Xe, 126Xe, and 134Xe are predicted to undergo double beta decay, but this has never been observed in these isotopes, so they are considered to be stable.) Xenon has the second highest number of stable isotopes. Only tin, with 10 stable isotopes, has more. Beyond these stable forms, there are over 30 unstable isotopes and isomers that have been studied, the longest-lived of which is 136Xe, which undergoes double beta decay with a half-life of 2.165 ± 0.016(stat) ± 0.059(sys) ×1021 years with the next longest lived being 127Xe with a half-life of 36.345 days. Of known isomers, the longest-lived is 131mXe with a half-life of 11.934 days. 129Xe is produced by beta decay of 129I (half-life: 16 million years); 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, and therefore used as indicators of nuclear explosions.The artificial isotope 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.65×106 barns, so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel).Relatively high concentrations of radioactive xenon isotopes are also found emanating from nuclear reactors due to the release of this fission gas from cracked fuel rods or fissioning of uranium in cooling water. The concentrations of these isotopes are still usually low compared to the naturally occurring radioactive noble gas 222Rn.Because xenon is a tracer for two parent isotopes, Xe isotope ratios in meteorites are a powerful tool for studying the formation of the solar system. The I-Xe method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the solar nebula (Xenon being a gas, only that part of it that formed after condensation will be present inside the object). Xenon isotopes are also a powerful tool for understanding terrestrial differentiation. Excess 129Xe found in carbon dioxide well gases from New Mexico was believed to be from the decay of mantle-derived gases soon after Earth's formation.All other isotopes have half-lives less than 12 days, most less than 20 hours. The shortest-lived isotope is 148Xe with a half-life of 408 ns. Its 41 isotopes have mass numbers ranging from 108 to 148.108Xe (disc. 2011) is the second heaviest nuclide with equal numbers of protons and neutrons, after 112Ba.

Naturally occurring titanium (22Ti) is composed of 5 stable isotopes; 46Ti, 47Ti, 48Ti, 49Ti and 50Ti with 48Ti being the most abundant (73.8% natural abundance). Twenty-one radioisotopes have been characterized, with the most stable being 44Ti with a half-life of 60 years, 45Ti with a half-life of 184.8 minutes, 51Ti with a half-life of 5.76 minutes, and 52Ti with a half-life of 1.7 minutes. All of the remaining radioactive isotopes have half-lives that are less than 33 seconds and the majority of these have half-lives that are less than half a second. The least stable is 61Ti with a half-life somewhat longer than 300 nanoseconds.The isotopes of titanium range in atomic mass from 38.01 u (38Ti) to 62.99 u (63Ti). The primary decay mode before the most abundant stable isotope, 48Ti, is β+ and the primary mode after is β−. The primary decay products before 48Ti are scandium isotopes and the primary products after are vanadium isotopes.

Meitnerium (109Mt) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 266Mt in 1982 (this is also the only isotope directly synthesized, all other isotopes are decay products of heavier elements). There are eight known isotopes, from 266Mt to 278Mt. There may also be two isomers. The longest-lived of the known isotopes is 278Mt with a half-life of 8 seconds.

Naturally occurring cobalt (27Co) is composed of 1 stable isotope, 59Co. 28 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.8 days, 56Co with a half-life of 77.27 days, and 58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second.

Osmium (76Os) has seven naturally occurring isotopes, 6 of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotope, 186Os, has an extremely long half-life (2×1015 years) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago.There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of 6 years, all others have half-lives under 94 days. There are also 9 known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours.

Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940. Twenty plutonium radioisotopes have been characterized.

Naturally occurring terbium (65Tb) is composed of 1 stable isotope, 159Tb. Thirty-six radioisotopes have been characterized, with the most stable being 158Tb with a half-life of 180 years, 157Tb with a half-life of 71 years, and 160Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lives that are less than 6.907 days, and the majority of these have half-lives that are less than 24 seconds.

There are twenty recognized isotopes of sodium (11Na), ranging from 18Na to 37Na and two isomers (22mNa and 24mNa). 23Na is the only stable (and the only primordial) isotope. As such, it is considered a monoisotopic element and it has a standard atomic weight of 22.98976928(2). Sodium has two radioactive cosmogenic isotopes (22Na, half-life = 2.605 years; and 24Na, half-life ≈ 15 hours). With the exception of those two, all other isotopes have half-lives under a minute, most under a second. The shortest-lived is 18Na, with a half-life of 1.3(4)×10−21 seconds.Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable 23Na in human blood plasma to 24Na. By measuring the concentration of this isotope, the neutron radiation dosage to the victim can be computed.22Na is a positron-emitting isotope with a remarkably long half-life. It is used to create test-objects and point-sources for positron emission tomography.

Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940. Twenty plutonium radioisotopes have been characterized. The most stable are Pu-244, with a half-life of 80.8 million years, Pu-242, with a half-life of 373,300 years, and Pu-239, with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. This element also has eight meta states, though none are very stable; all meta states have half-lives of less than one second.The isotopes of plutonium range in atomic weight from 228.0387 u (Pu-228) to 247.074 u (Pu-247). The primary decay modes before the most stable isotope, Pu-244, are spontaneous fission and alpha emission; the initial mode after is beta emission. The primary decay products before Pu-244 are isotopes of uranium and neptunium (neglecting the wide range of daughter nuclei created by fission processes), and the primary products after are isotopes of americium.

Naturally occurring scandium (21Sc) is composed of one stable isotope 45Sc. Twenty-four radioisotopes have been characterized with the most stable being 46Sc with a half-life of 83.8 days, 47Sc with a half-life of 3.35 days, and 48Sc with a half-life of 43.7 hours and Sc-44 with a half-life of 3.97 hours.

Curium (Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutrons. All of the isotopes are radioactive.There are 21 known radioisotopes with atomic masses ranging from 232Cm to 252Cm. There are also four known nuclear isomers (243mCm, 244mCm, 245mCm, and 249mCm).

Naturally occurring cerium (58Ce) is composed of 4 stable isotopes: 136Ce, 138Ce, 140Ce, and 142Ce, with 140Ce being the most abundant (88.48% natural abundance) and the only one theoretically stable; 136Ce, 138Ce, and 142Ce are predicted to undergo double beta decay but this process has never been observed.

Copernicium (112Cn) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 277Cn in 1996. There are 6 known radioisotopes and 2 possible isomers. The longest-lived isotope is 285Cn with a half-life of 29 seconds.

Naturally occurring tungsten (74W) consists of five isotopes. Four are considered stable (182W, 183W, 184W, and 186W) and one is slightly radioactive, 180W, with an extremely long half-life of 1.8 ± 0.2 Ea (1018 years). On average, two alpha decays of 180W occur per gram of natural tungsten per year so for most practical purposes tungsten can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so.

Einsteinium (99Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in nuclear fallout from an H-bomb test) was 253Es in 1952. There are 19 known radioisotopes from 240Es to 258Es, and 3 nuclear isomers (250mEs, 254mEs, and 256mEs). The longest-lived isotope is 252Es with a half-life of 471.7 days, or around 1.293 years.

Naturally occurring praseodymium (59Pr) is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr, with a half-life of 13.57 days and 142Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours and the majority of these have half-lives that are less than 33 seconds.

Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180mTa (0.012%).The latter nuclide 180mTa (m denotes a metastable state) has sufficient energy to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, and electron capture to 180Hf. However, no radioactivity from any decay mode of this nuclear isomer has ever been observed. Only a lower limit on its half-life of over 1015 years has been set, by observation. The very slow decay of 180mTa is attributed to its high spin (9 units) and the low spin of lower-lying states. Gamma or beta decay would require many units of angular momentum to be removed in a single step, so that the process would be very slow.The very unusual nature of 180mTa is that the ground state of this isotope is less stable than the isomer. The same property is exhibited in americium-242m (242mAm). 180Ta has a half-life of only 8 hours. 180mTa is the only naturally occurring nuclear isomer (excluding radiogenic and cosmogenic short-living nuclides). It is also the rarest primordial nuclide in the Universe observed for any element that has any stable isotopes.As of October 3, 2016 the half life of 180mTa is calculated to be least 45x1015 (45 million billion) years.There are also 35 known artificial radioisotopes, the longest-lived of which are 179Ta with a half-life of 1.82 years, 182Ta with a half-life of 114.43 days, 183Ta with a half-life of 5.1 days, and 177Ta with a half-life of 56.56 hours. All other isotopes have half-lives under a day, most under an hour. There are also numerous isomers, the most stable of which (other than 180mTa) is 178m1Ta with a half-life of 2.36 hours.Tantalum has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 181Ta, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 182Ta with a half-life of 114.43 days and produce approximately 1.12 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several months. Such a weapon is not known to have ever been built, tested, or used.

Although phosphorus (15P) has 23 isotopes from 24P to 46P, only one of these isotopes is stable 31P; as such, it is considered a monoisotopic element. The longest-lived radioactive isotopes are 33P with a half-life of 25.34 days and 32P with a half-life of 14.263 days. All other have half-lives under 2.5 minutes, most under a second. The least stable is 25P with a half-life shorter than 30 nanoseconds—the half-life of 24P is unknown.

Naturally occurring nickel (28Ni) is composed of five stable isotopes; 58Ni, 60Ni, 61Ni, 62Ni and 64Ni with 58Ni being the most abundant (68.077% natural abundance). 26 radioisotopes have been characterised with the most stable being 59Ni with a half-life of 76,000 years, 63Ni with a half-life of 100.1 years, and 56Ni with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lives that are less than 60 hours and the majority of these have half-lives that are less than 30 seconds. This element also has 1 meta state.

Lead (82Pb) has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively. These series represent the decay chain products of long-lived primordial U-238, U-235, and Th-232, respectively.

Bismuth (83Bi) has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as 208.98040(1). Although bismuth-209 is now known to be unstable, it has classically been considered to be a "stable" isotope because it has a half-life of over 1.9×1019 years, which is more than a billion (1000 million) times the age of the universe. Besides 209Bi, the most stable bismuth radioisotopes are 210mBi with a half-life of 3.04 million years, 208Bi with a half-life of 368,000 years and 207Bi, with a half-life of 32.9 years, none of which occur in nature. All other isotopes have half-lives under 1 year, most under a day. Of naturally occurring radioisotopes, the most stable is radiogenic 210Bi with a half-life of 5.012 days.Commercially the radioactive isotope bismuth-213 can be produced by bombarding radium with bremsstrahlung photons from a linear particle accelerator. In 1997 an antibody conjugate with Bi-213, which has a 45-minute half-life, and decays with the emission of an alpha-particle, was used to treat patients with leukemia. This isotope has also been tried in cancer treatment, e.g. in the Targeted Alpha Therapy (TAT) program. Bismuth-213 is also found on the decay chain of uranium-233.

Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over 3.1×1022 years), 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe. There are 24 known radioactive isotopes and their half-lives are shown below.

Promethium (61Pm) has no stable isotopes, and does not exist in nature, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu. It is a synthetic element, first produced in 1945. Thirty-eight radioisotopes have been characterized, with the most stable being 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years. All of the remaining radioactive isotopes have half-lives that are less than 365 days, and the majority of these have half-lives that are less than 30 seconds. This element also has 18 meta states with the most stable being 148mPm (t1/2 41.29 days), 152m2Pm (t1/2 13.8 minutes) and 152mPm (t1/2 7.52 minutes).The isotopes of promethium range in atomic weight from 125.95752 u (126Pm) to 162.95368 u (163Pm). The primary decay mode before the longest-lived isotope, 145Pm, is electron capture, and the primary mode after is beta decay. The primary decay products before 145Pm are isotopes of neodymium and the primary products after are isotopes of samarium.Since promethium does not exist in nature, a relative atomic mass cannot be given.

Arsenic (33As) has 33 known isotopes and at least 10 isomers. Only one of these isotopes, 75As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73As has a half-life of 80 days. Arsenic has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 75As, irradiated by the intense highenergy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 76As with a half-life of 1.0778 days and produce approximately 1.13 MeV gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several hours. Such a weapon is not known to have ever been built, tested, or used.

The alkaline earth metal strontium (38Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). It's standard atomic weight is 87.62(1).Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years (i.e. more than three times longer than the current age of the universe). Thus, there are two sources of 87Sr in any material: primordial, formed during nucleosynthesis along with 84Sr, 86Sr and 88Sr; and that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an electron configuration similar to that of calcium, it readily substitutes for Ca in minerals.In addition to the four stable isotopes, thirty-one unstable isotopes of Strontium are known to exist (see Table, below): the longest-lived of these are 90Sr with a half-life of 28.9 years and 85Sr with a half-life of 64.853 days. Of importance are strontium-89 (89Sr) with a half-life of 50.57 days, and strontium-90 (90Sr). They decay by emitting an electron and an antineutrino ( ν ¯ e {\displaystyle {\bar {\nu }}_{e}} ) in beta decay (β− decay) to become yttrium: 38 89 S r → 39 89 Y + e − + ν ¯ e {\displaystyle \mathrm {{}_{38}^{89}Sr} \rightarrow \mathrm {{}_{39}^{89}Y} +e^{-}+{\bar {\nu }}_{e}} 38 90 S r → 39 90 Y + e − + ν ¯ e {\displaystyle \mathrm {{}_{38}^{90}Sr} \rightarrow \mathrm {{}_{39}^{90}Y} +e^{-}+{\bar {\nu }}_{e}} 89Sr is an artificial radioisotope used in treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases, the administration of 89Sr results in the delivery of beta particles directly to the area of bony problem, where calcium turnover is greatest.90Sr is a by-product of nuclear fission, present in nuclear fallout. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. It causes health problems, as it substitutes for calcium in bone, preventing expulsion from the body. Because it is a long-lived high-energy beta emitter, it is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required.The lightest isotope is 73Sr and the heaviest is 107Sr.All other Strontium isotopes have half-lives shorter than 55 days, most under 100 minutes.

Technetium (43Tc) is the first of the two elements lighter than bismuth that have no non-radioactive isotopes; the other such element is promethium. It is primarily artificial, only trace quantities existing in nature produced by spontaneous fission or neutron capture by molybdenum. The first isotopes to be synthesized were 97Tc and 99Tc in 1936, the first artificial element to be produced.

Fermium (100Fm) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in fallout from nuclear testing) was 255Fm in 1952. 250Fm was independently synthesized shortly after the discovery of 255Fm. There are 20 known radioisotopes ranging in atomic mass from 241Fm to 260Fm (260Fm is unconfirmed), and 2 nuclear isomers, 250mFm and 251mFm.

Sulfur (16S) has 24 known isotopes with mass numbers ranging from 26 to 49, four of which are stable: 32S (95.02%), 33S (0.75%), 34S (4.21%), and 36S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium nuclei, in the so-called alpha process of exploding type II supernovae (see silicon burning).Other than 35S, the radioactive isotopes of sulphur are all comparatively short-lived.

Naturally occurring lutetium (71Lu) is composed of 1 stable isotope 175Lu (97.41% natural abundance) and one long-lived radioisotope, 176Lu with a half-life of 3.78 × 1010 years (2.59% natural abundance). Thirty-four radioisotopes have been characterized, with the most stable, besides 176Lu, being 174Lu with a half-life of 3.31 years, and 173Lu with a half-life of 1.37 years.

Roentgenium (111Rg) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 272Rg in 1994, which is also the only directly synthesized isotope, all others are decay products of nihonium, moscovium, and tennessine. There are 7 known radioisotopes from 272Rg to 282Rg. The longest-lived isotope is 282Rg with a half-life of 2.1 minutes, although the unconfirmed 286Rg may have a longer half-life of about 11 minutes.

Naturally occurring thulium (69Tm) is composed of 1 stable isotope, 169Tm (100% natural abundance). Thirty-four radioisotopes have been characterized, with the most stable being 171Tm with a half-life of 1.92 years, 170Tm with a half-life of 128.6 days, 168Tm with a half-life of 93.1 days, and 167Tm with a half-life of 9.25 days. All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half-lives that are less than 2 minutes. This element also has 26 meta states, with the most stable being 164mTm (t1/2 5.1 minutes), 160mTm (t1/2 74.5 seconds) and 155mTm (t1/2 45 seconds).The isotopes of thulium range in atomic weight from 144.97007 u (145Tm) to 178.95534 u (179Tm). The primary decay mode before the most abundant stable isotope, 169Tm, is electron capture, and the primary mode after is beta emission. The primary decay products before 169Tm are erbium isotopes, and the primary products after are ytterbium isotopes.

Osmium (76Os) has seven naturally occurring isotopes, 6 of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotope, 186Os, has an extremely long half-life (2×1015 years) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio.

Copper (29Cu) has two stable isotopes, 63Cu and 65Cu, along with 27 radioisotopes. The most stable of these is 67Cu with a half-life of 61.83 hours. The least stable is 54Cu with a half-life of approximately 75 ns. Most have half-lives under a minute. Unstable copper isotopes with atomic masses below 63 tend to undergo β+ decay, while isotopes with atomic masses above 65 tend to undergo β− decay. 64Cu decays by both β+ and β−.68Cu, 69Cu, 71Cu, 72Cu, and 76Cu each have one metastable isomer. 70Cu has two isomers, making a total of 7 distinct isomers. The most stable of these is 68mCu with a half-life of 3.75 minutes. The least stable is 69mCu with a half-life of 360 ns.

Natural hafnium (72Hf) consists of five stable isotopes (176Hf, 177Hf, 178Hf, 179Hf, and 180Hf) and one very long-lived radioisotope, 174Hf, with a half-life of 2×1015 years. In addition, there are 30 other known radionuclides, the most stable of which is 182Hf with a half-life of 8.9×106 years. No other radioisotope has a half-life over 1.87 days. Most isotopes have half-lives under 1 minute. There are also 26 known nuclear isomers, the most stable of which is 178m2Hf with a half-life of 31 years.

There are 37 known isotopes of iodine (53I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element.Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide.

Mendelevium (101Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 256Md (which was also the first isotope of any element produced one atom at a time) in 1955. There are 16 known radioisotopes, ranging in atomic mass from 245Md to 260Md, and 5 isomers. The longest-lived isotope is 258Md with a half-life of 51.3 days, and the longest-lived isomer is 258mMd with a half-life of 58.0 minutes.

Isothecium myosuroides, commonly known as slender mouse-tail moss or tree moss, is a true moss that grows abundantly on both rocks and trees. It is native to Eastern North America. It grows preferentially on angiosperms rather than on conifers because of the manner in which the former take in water creating an ideal moist habitat for the moss to grow on, and because many trees in the flowering plant families are less acidic than coniferous species of trees.

Naturally occurring vanadium (23V) is composed of one stable isotope 51V and one radioactive isotope 50V with a half-life of 1.5×1017 years. 24 artificial radioisotopes have been characterized (in the range of mass number between 40 and 65) with the most stable being 49V with a half-life of 330 days, and 48V with a half-life of 15.9735 days. All of the remaining radioactive isotopes have half-lives shorter than an hour, the majority of them below 10 seconds, the least stable being 42V with a half-life shorter than 55 nanoseconds, with all of the isotopes lighter than it, and none of the heavier, have unknown half-lives. In 4 isotopes, metastable excited states were found (including 2 metastable states for 60V), which adds up to 5 meta states.The primary decay mode before the most abundant stable isotope 51V is electron capture. The next most common mode is beta decay. The primary decay products before 51V are element 22 (titanium) isotopes and the primary products after are element 24 (chromium) isotopes.

Nobelium (102No) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized (and correctly identified) was 254No in 1966. There are 12 known radioisotopes, which are 250No to 260No and 262No, and 3 isomers, 251mNo, 253mNo, and 254mNo. The longest-lived isotope is 259No with a half-life of 58 minutes. The longest-lived isomer is 251mNo with a half-life of 1.7 seconds.

Naturally occurring manganese (25Mn) is composed of 1 stable isotope, 55Mn. 25 radioisotopes have been characterized with the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the remaining radioactive isotopes have half-lives that are less than 3 hours and the majority of these have half-lives that are less than 1 minute, but only 45Mn has an unknown half-life.

Boron (5B) naturally occurs as isotopes 10B and 11B, the latter of which makes up about 80% of natural boron. There are 14 radioisotopes that have been discovered, with mass numbers from 6 to 21, all with short half-lives, the longest being that of 8B, with a half-life of only 770 milliseconds (ms) and 12B with a half-life of 20.2 ms. All other isotopes have half-lives shorter than 17.35 ms, with the least stable isotope being 7B, with a half-life of 150 yoctoseconds (ys). Those isotopes with mass below 10 decay into helium (via short-lived isotopes of beryllium for 7B and 9B) while those with mass above 11 mostly become carbon.

Naturally occurring Ytterbium (70Yb) is composed of 7 stable isotopes, 168Yb, 170Yb, 171Yb, 172Yb, 173Yb, 174Yb, and 176Yb, with 174Yb being the most abundant (31.83% natural abundance). Twenty-seven radioisotopes have been characterized, with the most stable being 169Yb with a half-life of 32.026 days, 175Yb with a half-life of 4.185 days, and 166Yb with a half-life of 56.7 hours. All of the remaining radioactive isotopes have half-lives that are less than 2 hours, and the majority of these have half-lives that are less than 20 minutes. This element also has 12 meta states, with the most stable being 169mYb (t1/2 46 seconds).The isotopes of ytterbium range in atomic weight from 147.967 u (148Yb) to 180.9562 u (181Yb). The primary decay mode before the most abundant stable isotope, 174Yb is electron capture, and the primary mode after is beta emission. The primary decay products before 174Yb are isotopes of thulium, and the primary products after are isotopes of lutetium. Of interest to modern quantum optics, the different ytterbium isotopes follow either Bose–Einstein statistics or Fermi–Dirac statistics, leading to interesting behavior in optical lattices.

Neptunium (Np) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes.

Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180mTa (0.012%).The latter nuclide 180mTa (m denotes a metastable state) has sufficient energy to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, and electron capture to 180Hf. However, no radioactivity from any decay mode of this nuclear isomer has ever been observed. Only a lower limit on its half-life of over 1015 years has been set, by observation.

Argon (18Ar) has 24 known isotopes, from 30Ar to 53Ar and 1 isomer (32mAr), three of which are stable, 36Ar, 38Ar, and 40Ar. On the Earth, 40Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are 39Ar with a half-life of 269 years, 42Ar with a half-life of 32.9 years, and 37Ar with a half-life of 35.04 days. All other isotopes have half-lives less than two hours, and most less than one minute. The least stable is 30Ar with a half-life shorter than 20 nanoseconds.The naturally occurring 40K, with a half-life of 1.248×109 years, decays to stable 40Ar (10.72%) by electron capture and by positron emission, and also transforms to stable 40Ca (89.28%) via beta decay. These properties and ratios are used to determine the age of rocks through potassium-argon dating.Despite the trapping of 40Ar in many rocks, it can be released by melting, grinding, and diffusion. Almost all of the argon in the Earth's atmosphere is the product of potassium-40 decay, since 99.6% of Earth atmospheric argon is 40Ar, whereas in the Sun and presumably in primordial star-forming clouds, argon consists of < 15% 38Ar and mostly (85%) 36Ar. Similarly, the ratio of the three isotopes 36Ar:38Ar:40Ar in the atmospheres of the outer planets is measured to be 8400:1600:1.In the Earth's atmosphere, radioactive 39Ar (half-life 269 years) is made by cosmic ray activity, primarily from 40Ar. In the subsurface environment, it is also produced through neutron capture by 39K or alpha emission by calcium. The content of 39Ar in natural argon is measured to be of (8.0±0.6)×10−16 g/g, or (1.01±0.08) Bq/kg of 36, 38, 40Ar. The content of 42Ar (half-life 33 years) in the Earth's atmosphere is lower than 6×10−21 parts per part of 36, 38, 40Ar. Many endeavors require argon depleted in the cosmogenic isotopes, known as depleted argon. In December 2013, 36Ar, in the form of argon hydride, was found in cosmic dust associated with the Crab nebula supernova. This was the first time a noble molecule was detected in outer space.Radioactive 37Ar is a synthetic radionuclide that is created from the neutron capture by 40Ca followed by an alpha particle emission as a result of subsurface nuclear explosions. It has a half-life of 35 days.

Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). There are 38 radioisotopes that have been characterized, with the most stable being 138La, with a half-life of 102×109 years; 137La, with a half-life of 60,000 years and 140La, with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 minute. This element also has 12 nuclear isomers, the longest-lived of which is 132mLa, with a half-life of 24.3 minutes.The isotopes of lanthanum range in atomic weight from 116.95 u (117La) to 154.96 u (155La).

Naturally occurring rhenium (75Re) is 37.4% 185Re, which is stable, and 62.6% 187Re, which is unstable but has a very long half-life (41.2×109 years). Among elements with a known stable isotope, only indium and tellurium similarly occur with a stable isotope in lower abundance than the long-lived radioactive isotope.There are 33 other unstable isotopes recognized, the longest-lived of which are 183Re with a half-life of 70 days, 184Re with a half-life of 38 days, 186Re with a half-life of 3.7186 days, 182Re with a half-life of 64.0 hours, and 189Re with a half-life of 24.3 hours. There are also numerous isomers, the longest-lived of which are 186mRe with a half-life of 200,000 years and 184mRe with a half-life of 169 days. All others have half-lives less than a day.

Naturally occurring thulium (69Tm) is composed of 1 stable isotope, 169Tm (100% natural abundance). Thirty-four radioisotopes have been characterized, with the most stable being 171Tm with a half-life of 1.92 years, 170Tm with a half-life of 128.6 days, 168Tm with a half-life of 93.1 days, and 167Tm with a half-life of 9.25 days. All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half-lives that are less than 2 minutes.

Naturally occurring europium (63Eu) is composed of 2 isotopes, 151Eu and 153Eu, with 153Eu being the most abundant (52.2% natural abundance). While 153Eu is observationally stable, 151Eu was recently found to be unstable and to undergo alpha decay. The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 y which corresponds to 1 alpha decay per two minutes in every kilogram of natural europium. Besides natural radioisotope 151Eu, 36 artificial radioisotopes have been characterized, with the most stable being 150Eu with a half-life of 36.9 years, 152Eu with a half-life of 13.516 years, and 154Eu with a half-life of 8.593 years. All of the remaining radioactive isotopes have half-lives that are less than 4.7612 years, and the majority of these have half-lives that are less than 12.2 seconds. This element also has 17 meta states, with the most stable being 150mEu (t1/2 12.8 hours), 152m1Eu (t1/2 9.3116 hours) and 152m2Eu (t1/2 96 minutes).The primary decay mode before the most abundant stable isotope, 153Eu, is electron capture, and the primary mode after is beta decay. The primary decay products before 153Eu are isotopes of samarium and the primary products after are isotopes of gadolinium.

Natural nitrogen (7N) consists of two stable isotopes, nitrogen-14, which makes up the vast majority of naturally occurring nitrogen, and nitrogen-15. Fourteen radioactive isotopes (radioisotopes) have also been found so far, with atomic masses ranging from 10 to 25, and one nuclear isomer, 11mN. All of these radioisotopes are short-lived, with the longest-lived one being nitrogen-13 with a half-life of 9.965 minutes.

Although there are nine known isotopes of helium (2He) (standard atomic weight: 4.002602(2)), only helium-3 (3He) and helium-4 (4He) are stable. All radioisotopes are short-lived, the longest-lived being 6He with a half-life of 806.7 milliseconds. The least stable is 5He, with a half-life of 7.6×10−22 s, although it is possible that 2He has an even shorter half-life.In the Earth's atmosphere, there is one 3He atom for every million 4He atoms.

Naturally occurring xenon (54Xe) is made of eight stable isotopes and one very long-lived isotope. (124Xe, 126Xe, and 134Xe are predicted to undergo double beta decay, but this has never been observed in these isotopes, so they are considered to be stable.) Xenon has the second highest number of stable isotopes. Only tin, with 10 stable isotopes, has more.

Berkelium (97Bk) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 243Bk in 1949. There are 20 known radioisotopes, from 235Bk to 254Bk, and 6 nuclear isomers. The longest-lived isotope is 247Bk with a half-life of 1,380 years.

Naturally occurring silver (47Ag) is composed of the two stable isotopes 107Ag and 109Ag with 107Ag being the more abundant (51.839% natural abundance). Twenty-eight radioisotopes have been characterized with the most stable being 105Ag with a half-life of 41.29 days, 111Ag with a half-life of 7.45 days, and 112Ag with a half-life of 3.13 hours.All of the remaining radioactive isotopes have half-lives that are less than an hour and the majority of these have half-lives that are less than 3 minutes. This element has numerous meta states with the most stable being 108mAg (t* 418 years), 110mAg (t* 249.79 days) and 106mAg (t* 8.28 days).Isotopes of silver range in atomic weight from 92.950 u (93Ag) to 129.950 u (130Ag). The primary decay mode before the most abundant stable isotope, 107Ag, is electron capture and the primary mode after is beta decay. The primary decay products before 107Ag are palladium (element 46) isotopes and the primary products after are cadmium (element 48) isotopes.The palladium isotope 107Pd decays by beta emission to 107Ag with a half-life of 6.5 million years. Iron meteorites are the only objects with a high enough palladium/silver ratio to yield measurable variations in 107Ag abundance. Radiogenic 107Ag was first discovered in the Santa Clara meteorite in 1978.The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus 107Ag correlations observed in bodies, which have clearly been melted since the accretion of the solar system, must reflect the presence of live short-lived nuclides in the early solar system.

Francium (87Fr) has no stable isotopes. A standard atomic weight cannot be given. Its most stable isotope is 223Fr with a half-life of 22 minutes, occurring in trace quantities as an intermediate decay product of 235U. The other natural isotope is 221Fr.Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable.

Actinium (89Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 31 known isotopes, from 206Ac to 236Ac, and 2 isomers. Two isotopes are found in nature, 227Ac and 228Ac, as intermediate decay products of, respectively, 235U and 232Th.

Isotope lists, all if you want a list with separate chart by the atomic number, see Isotope lists.

Magnesium (12Mg) naturally occurs in three stable isotopes, 24Mg, 25Mg, and 26Mg. There are 19 radioisotopes that have been discovered, ranging from 19Mg to 40Mg. The longest-lived radioisotope is 28Mg with a half-life of 20.915 hours. The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium. The shortest-lived is 39Mg with a half-life shorter than 180 nanoseconds, or possibly 40Mg, with a half-life longer than 170 nanoseconds (the half-life of 19Mg is unknown).

Darmstadtium (110Ds) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 269Ds in 1994. There are 7 or 8 known radioisotopes from 267Ds (or 269Ds) to 281Ds (with many gaps) and 2 or 3 known isomers. The longest-lived isotope is 281Ds with a half-life of 9.6 seconds.

Tennessine (117Ts) is the most-recently synthesized synthetic element, and much of the data is hypothetical. As any synthetic element, a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotopes to be synthesized were 293Ts and 294Ts in 2009. The longer-lived isotope is 294Ts with a half-life of 51 ms.

Germanium (32Ge) has five naturally Elijah Jeffersonisotopes, 70Ge, 72Ge, 73Ge, 74Ge, and 76Ge. Of these, 76Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 1021 years (130 billion times the age of the universe).Stable 74Ge is the most common isotope, having a natural abundance of approximately 36%. 76Ge is the least common with a natural abundance of approximately 7%.

Natural yttrium (39Y) is composed of a single isotope yttrium-89. The most stable radioisotopes are 88Y, which has a half-life of 106.6 days and 91Y with a half-life of 58.51 days. All the other isotopes have half-lives of less than a day, except 87Y, which has a half-life of 79.8 hours, and 90Y, with 64 hours. The dominant decay mode below the stable 89Y is electron capture and the dominant mode after it is beta emission. Twenty-six unstable isotopes have been characterized.90Y exists in equilibrium with its parent isotope strontium-90, which is a product of nuclear fission.

Hassium (108Hs) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 265Hs in 1984. There are 12 known isotopes from 263Hs to 277Hs and 1–4 isomers. The longest-lived isotope is 269Hs with a half-life of 9.6 seconds.

Flerovium (114Fl) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 289Fl in 1999 (or possibly 1998). Flerovium has six known isotopes, and possibly 2 nuclear isomers. The longest-lived isotope is 289Fl with a half-life of 1.9 seconds, but the unconfirmed 290Fl may have a longer half-life of 19 seconds.

Isotope lists

Natural nitrogen (7N) consists of two stable isotopes, nitrogen-14, which makes up the vast majority of naturally occurring nitrogen, and nitrogen-15. Fourteen radioactive isotopes (radioisotopes) have also been found so far, with atomic masses ranging from 10 to 25, and one nuclear isomer, 11mN. All of these radioisotopes are short-lived, with the longest-lived one being nitrogen-13 with a half-life of 9.965 minutes. All of the others have half-lives below 7.15 seconds, with most of these being below five-eighths of a second. Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of about 2.3 microseconds.The relative atomic mass of nitrogen is 14.0067.

Magnesium (12Mg) naturally occurs in three stable isotopes, 24Mg, 25Mg, and 26Mg. There are 19 radioisotopes that have been discovered, ranging from 19Mg to 40Mg. The longest-lived radioisotope is 28Mg with a half-life of 20.915 hours. The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium.

Naturally occurring rhenium (75Re) is 37.4% 185Re, which is stable, and 62.6% 187Re, which is unstable but has a very long half-life (41.2×109 years).

Natural holmium (67Ho) contains one stable isotope, 165Ho. A number of synthetic radioactive isotopes are known, the most stable one is 163Ho, with a half-life of 4,570 years. All other radioisotopes have half-lives not greater than 1.117 days in their ground states (although the metastable 166mHo has a half-life of about 1,200 years), and most have half-lives under 3 hours.

Naturally occurring cerium (58Ce) is composed of 4 stable isotopes: 136Ce, 138Ce, 140Ce, and 142Ce, with 140Ce being the most abundant (88.48% natural abundance) and the only one theoretically stable; 136Ce, 138Ce, and 142Ce are predicted to undergo double beta decay but this process has never been observed. There are 35 radioisotopes that have been characterized, with the most stable being 144Ce, with a half-life of 284.893 days; 139Ce, with a half-life of 137.640 days and 141Ce, with a half-life of 32.501 days. All of the remaining radioactive isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than 10 minutes. This element also has 10 meta states.The isotopes of cerium range in atomic weight from 119 u (119Ce) to 157 u (157Ce).

Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 900 years.

Americium (Am) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no known stable isotopes. The first isotope to be synthesized was 241Am in 1944. The artificial element decays into alpha particles.

Neon (10Ne) possesses three stable isotopes, 20Ne, 21Ne, and 22Ne. In addition, 16 radioactive isotopes have been discovered ranging from 16Ne to 34Ne, all short-lived. The longest-lived is 24Ne with a half-life of 3.38 minutes. All others are under a minute, most under a second. The least stable is 16Ne with a half-life of 9×10−21 s. See isotopes of carbon for notes about the measurement.

There are seven stable isotopes of mercury (80Hg) with 202Hg being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining 32 radioisotopes have half-lives that are less than a day.

April

Rutherfordium (104Rf) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was either 259Rf in 1966 or 257Rf in 1969. There are 16 known radioisotopes from 253Rf to 270Rf (3 of which, 266Rf, 268Rf, and 270Rf are unconfirmed) and 4 isomers. The longest-lived isotope is 267Rf with an estimated half-life of 5 hours.

Isotope lists, 73-96 if you want a list with just one giant list of isotopes, see Isotope lists, all.

Moscovium (115Mc) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 288Mc in 2004. There are four known radioisotopes from 287Mc to 290Mc.

Indium (49In) consists of two primordial nuclides, with the most common (~ 95.7%) nuclide (115In) being measurably though weakly radioactive. Its spin-forbidden decay has a half life of 441 trillion years.The stable isotope 113In is only 4.3% of naturally occurring indium. Among elements with a known stable isotope, only tellurium and rhenium similarly occur with a stable isotope in lower abundance than the long-lived radioactive isotope.

Isotones

Radium (88Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1,600 years. 226Ra occurs in the decay chain of 238U (often referred to as the radium series.) Radium has 33 known isotopes from 202Ra to 234Ra.

Tin (50Sn) is the element with the greatest number of stable isotopes (ten; three of them are potentially radioactive but have not been observed to decay), which is probably related to the fact that 50 is a "magic number" of protons. 29 additional unstable isotopes are known, including the "doubly magic" tin-100 (100Sn) (discovered in 1994) and tin-132 (132Sn). The longest-lived radioisotope is 126Sn, with a half-life of 230,000 years. The other 28 radioisotopes have half-lives less than a year.

Naturally occurring lithium (3Li, standard atomic weight: [6.938, 6.997], conventional: 6.94) is composed of two stable isotopes, lithium-6 and lithium-7, with the latter being far more abundant: about 92.5 percent of the atoms. Both of the natural isotopes have an unexpectedly low nuclear binding energy per nucleon (~5.3 MeV) when compared with the adjacent lighter and heavier elements, helium (~7.1 MeV) and beryllium (~6.5 MeV). The longest-lived radioisotope of lithium is lithium-8, which has a half-life of just 838 milliseconds. Lithium-9 has a half-life of 178 milliseconds, and lithium-11 has a half-life of about 8.6 milliseconds. All of the remaining isotopes of lithium have half-lives that are shorter than 10 nanoseconds. The shortest-lived known isotope of lithium is lithium-4, which decays by proton emission with a half-life of about 9.1×10−23 seconds, although the half-life of lithium-3 is yet to be determined, and is likely to be much shorter.Lithium-7 and lithium-6 are two of the primordial nuclides that were produced in the Big Bang, with lithium-7 to be 10−9 of all primordial nuclides and amount of lithium-6 around 10−13. A small percentage of lithium-6 is also known to be produced by nuclear reactions in certain stars. The isotopes of lithium separate somewhat during a variety of geological processes, including mineral formation (chemical precipitation and ion exchange). Lithium ions replace magnesium or iron in certain octahedral locations in clays, and lithium-6 is sometimes preferred over lithium-7. This results in some enrichment of lithium-7 in geological processes.Lithium-6 is an important isotope in nuclear physics because when it is bombarded with neutrons, tritium is produced.

Naturally occurring barium (56Ba) is a mix of six stable isotopes and one very long-lived radioactive primordial isotope, barium-130, recently identified as being unstable by geochemical means (from analysis of the presence of its daughter xenon-130 in rocks). This nuclide decays by double-electron capture (absorbing two electrons and emitting two neutrons;) with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe).There are a total of thirty-three known radioisotopes in addition to 130Ba, but most of these are highly radioactive with half-lives in the several millisecond to several minute range. The only notable exceptions are 133Ba, which has a half-life of 10.51 years, 131Ba (11.5 days), and 137mBa (2.55 minutes), which is the decay product of 137Cs (30.17 years, and a common fission product).Barium-114 is predicted to undergo cluster decay, emitting a nucleus of stable 12C to produce 102Sn. However this decay is not yet observed; the upper limit on the branching ratio of such decay is 0.0034%.

Calcium (20Ca) has 24 isotopes, from 34Ca to 57Ca. There are five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one isotope (48Ca) with such a long half-life that for all practical purposes it can be considered stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 102,000 years. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Most of its production is in the upper metre or so of the soil column, where the cosmogenic neutron flux is still sufficiently strong. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar-system anomalies. The most stable artificial radioisotope is 45Ca, with a half-life of 163 days.All other isotopes have half-lives of 163 days or less, most under a minute. The least stable is 34Ca with a half-life shorter than 35 nanoseconds.40Ca comprises about 97% of naturally occurring calcium. 40Ca is also one of the daughter products of 40K decay, along with 40Ar. While K-Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K–Ca age dating.

Although there are nine known isotopes of helium (2He) (standard atomic weight: 4.002602(2)), only helium-3 (3He) and helium-4 (4He) are stable. All radioisotopes are short-lived, the longest-lived being 6He with a half-life of 806.7 milliseconds. The least stable is 5He, with a half-life of 7.6×10−22 s, although it is possible that 2He has an even shorter half-life.In the Earth's atmosphere, there is one 3He atom for every million 4He atoms. However, helium is unusual in that its isotopic abundance varies greatly depending on its origin. In the interstellar medium, the proportion of 3He is around a hundred times higher. Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten; this is used in geology to investigate the origin of rocks and the composition of the Earth's mantle. The different formation processes of the two stable isotopes of helium produce the differing isotope abundances.Equal mixtures of liquid 3He and 4He below 0.8 K will separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics: 4He atoms are bosons while 3He atoms are fermions). Dilution refrigerators take advantage of the immiscibility of these two isotopes to achieve temperatures of a few millikelvins.

Silicon (14Si) has 24 known isotopes, with mass numbers ranging from 22 to 45. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years (0.21 MeV), and it decays by beta emission to 32P (which has a 14.28 day half-life [1]) and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds. The relative atomic mass is 28.0855(3). The least stable is usually 43Si with a half-life greater than 60 nanoseconds.

The chemical element selenium (34Se) has six naturally occurring isotopes, five of which are stable: 74Se, 76Se, 77Se, 78Se, and 80Se. The last three also occur as fission products, along with 79Se, which has a half-life of 327,000 years, and 82Se, which has a very long half-life (~1020 years, decaying via double beta decay to 82Kr) and for practical purposes can be considered to be stable.

Oganesson (118Og) is a synthetic element created in particle accelerators, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotope to be synthesized was 294Og in 2006; it has a half-life of 0.7 milliseconds.

Rutherfordium (104Rf) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was either 259Rf in 1966 or 257Rf in 1969. There are 16 known radioisotopes from 253Rf to 270Rf (3 of which, 266Rf, 268Rf, and 270Rf are unconfirmed) and 4 isomers. The longest-lived isotope is 267Rf with an estimated half-life of 5 hours. The longest directly measured half-life is 263Rf at 11 minutes, and the longest-lived isomer is 261mRf with a half-life of 81 seconds.

Copper (29Cu) has two stable isotopes, 63Cu and 65Cu, along with 27 radioisotopes. The most stable of these is 67Cu with a half-life of 61.83 hours. The least stable is 54Cu with a half-life of approximately 75 ns. Most have half-lives under a minute. Unstable copper isotopes with atomic masses below 63 tend to undergo β+ decay, while isotopes with atomic masses above 65 tend to undergo β− decay. 64Cu decays by both β+ and β−.68Cu, 69Cu, 71Cu, 72Cu, and 76Cu each have one metastable isomer.

Bromine (35Br) has two stable isotopes, 79Br and 81Br, and 30 known radioisotopes, the most stable of which is 77Br, with a half-life of 57.036 hours. Bromine and chlorine are the only halogens with more than one stable isotope.

Naturally occurring cadmium (48Cd) is composed of 8 isotopes. For two of them, natural radioactivity was observed, and three others are predicted to be radioactive but their decays were never observed, due to extremely long half-life times. The two natural radioactive isotopes are 113Cd (beta decay, half-life is 8.04 × 1015 years) and 116Cd (two-neutrino double beta decay, half-life is 2.8 × 1019 years). The other three are 106Cd, 108Cd (double electron capture), and 114Cd (double beta decay); only lower limits on their half-life times have been set. At least three isotopes—110Cd, 111Cd, and 112Cd—are absolutely stable (except, theoretically, to spontaneous fission). Among the isotopes absent in the natural cadmium, the most long-lived are 109Cd with a half-life of 462.6 days, and 115Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives that are less than 2.5 hours and the majority of these have half-lives that are less than 5 minutes. This element also has 8 known meta states with the most stable being 113mCd (t1/2 14.1 years), 115mCd (t1/2 44.6 days) and 117mCd (t1/2 3.36 hours).The known isotopes of cadmium range in atomic mass from 94.950 u (95Cd) to 131.946 u (132Cd). The primary decay mode before the second most abundant stable isotope, 112Cd, is electron capture and the primary modes after are beta emission and electron capture. The primary decay product before 112Cd is element 47 (silver) and the primary product after is element 49 (indium).

Naturally occurring zirconium (40Zr) is composed of four stable isotopes (of which one may in the future be found radioactive), and one very long-lived radioisotope (96Zr), a primordial nuclide that decays via double beta decay with an observed half-life of 2.0×1019 years; it can also undergo single beta decay, which is not yet observed, but the theoretically predicted value of t1/2 is 2.4×1020 years. The second most stable radioisotope is 93Zr, which has a half-life of 1.53 million years.

Rubidium (37Rb) has 32 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%). Normal mixes of rubidium are radioactive enough to fog photographic film in approximately 30 to 60 days.87Rb has a half-life of 4.92×1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread.

Dubnium (105Db) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 261Db in 1968. There are 13 known radioisotopes from 255Db to 270Db, and 1–3 isomers. The 105longest-lived known isotope is 268Db with a half-life of 29 hours.

There are 33 known isotopes of molybdenum (42Mo) ranging in atomic mass from 83 to 115, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, six (all but 100Mo) have never been observed to decay, but all are theoretically capable of radioactive decay. All unstable isotopes of molybdenum decay into isotopes of zirconium, niobium, technetium, and ruthenium.Molybdenum-100 is the only naturally occurring isotope that is not stable. Molybdenum-100 has a half-life of approximately 1×1019 y and undergoes double beta decay into ruthenium-100. Molybdenum-98 is the most common isotope, comprising 24.14% of all molybdenum on Earth. Molybdenum isotopes with mass numbers 111 and up all have half-lives of approximately .15 µs.

Natural yttrium (39Y) is composed of a single isotope yttrium-89. The most stable radioisotopes are 88Y, which has a half-life of 106.6 days and 91Y with a half-life of 58.51 days. All the other isotopes have half-lives of less than a day, except 87Y, which has a half-life of 79.8 hours, and 90Y, with 64 hours. The dominant decay mode below the stable 89Y is electron capture and the dominant mode after it is beta emission.

Carbon (6C) has 15 known isotopes, from 8C to 22C, of which 12C and 13C are stable. The longest-lived radioisotope is 14C, with a half-life of 5,700 years. This is also the only carbon radioisotope found in nature—trace quantities are formed cosmogenically by the reaction 14N + 1n → 14C + 1H. The most stable artificial radioisotope is 11C, which has a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds.

Naturally occurring chromium (24Cr) is composed of four stable isotopes; 50Cr, 52Cr, 53Cr, and 54Cr with 52Cr being the most abundant (83.789% natural abundance). 50Cr is suspected of decaying by β+β+ to 50Ti with a half-life of (more than) 1.8x1017 years. Twenty-two radioisotopes, all of which are entirely synthetic, have been characterized with the most stable being 51Cr with a half-life of 27.7 days. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half-lives that are less than 1 minute, the least stable being 66Cr with a half-life of 10 milliseconds. This element also has 2 meta states, 45Crm, the more stable one, and 59Crm, the least stable isotope or isomer.53Cr is the radiogenic decay product of 53Mn. Chromium isotopic contents are typically combined with manganese isotopic contents and have found application in isotope geology. Mn-Cr isotope ratios reinforce the evidence from 26Al and 107Pd for the early history of the solar system. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate an initial 53Mn/55Mn ratio that suggests Mn-Cr isotope systematics must result from in-situ decay of 53Mn in differentiated planetary bodies. Hence 53Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system. The same isotope is preferentially involved in certain leaching reactions, thereby allowing its abundance in seawater sediments to be used as a proxy for atmospheric oxygen concentrations.The isotopes of chromium range from 42Cr to 67Cr. The primary decay mode before the most abundant stable isotope, 52Cr, is electron capture and the primary mode after is beta decay.

Calcium (20Ca) has 24 isotopes, from 34Ca to 57Ca. There are five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one isotope (48Ca) with such a long half-life that for all practical purposes it can be considered stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 102,000 years.

Bohrium (107Bh) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 262Bh in 1981. There are 11 known isotopes ranging from 260Bh to 274Bh, and 1 isomer, 262mBh. The longest-lived isotope is 270Bh with a half-life of 1 minute.

Naturally occurring terbium (65Tb) is composed of 1 stable isotope, 159Tb. Thirty-six radioisotopes have been characterized, with the most stable being 158Tb with a half-life of 180 years, 157Tb with a half-life of 71 years, and 160Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lives that are less than 6.907 days, and the majority of these have half-lives that are less than 24 seconds. This element also has 27 meta states, with the most stable being 156m1Tb (t1/2 24.4 hours), 154m2Tb (t1/2 22.7 hours) and 154m1Tb (t1/2 9.4 hours).The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture, and the primary mode behind is beta decay. The primary decay products before 159Tb are element Gd (gadolinium) isotopes, and the primary products behind are element Dy (dysprosium) isotopes.

Antimony (51Sb) occurs in two stable isotopes, 121Sb and 123Sb. There are 35 artificial radioactive isotopes, the longest-lived of which are 125Sb, with a half-life of 2.75856 years; 124Sb, with a half-life of 60.2 days; and 126Sb, with a half-life of 12.35 days. All other isotopes have half-lives less than 4 days, most less than an hour.There are also many isomers, the longest-lived of which is 120m1Sb with a half-life of 5.76 days.

Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). There are 38 radioisotopes that have been characterized, with the most stable being 138La, with a half-life of 102×109 years; 137La, with a half-life of 60,000 years and 140La, with a half-life of 1.6781 days.

The chemical element selenium (34Se) has six naturally occurring isotopes, five of which are stable: 74Se, 76Se, 77Se, 78Se, and 80Se. The last three also occur as fission products, along with 79Se, which has a half-life of 327,000 years, and 82Se, which has a very long half-life (~1020 years, decaying via double beta decay to 82Kr) and for practical purposes can be considered to be stable. There are 23 other unstable isotopes that have been characterized, the longest-lived being 79Se with a half-life 327,000 years, 75Se with a half-life of 120 days, and 72Se with a half-life of 8.40 days. Of the other isotopes, 73Se has the longest half-life, 7.15 hours; most others have half-lives not exceeding 38 seconds.

There are 33 known isotopes of molybdenum (42Mo) ranging in atomic mass from 83 to 115, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, six (all but 100Mo) have never been observed to decay, but all are theoretically capable of radioactive decay.

Template:Infobox neodynium isotopes Naturally occurring neodymium (60Nd) is composed of 5 stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% natural abundance), and 2 long-lived radioisotopes, 144Nd and 150Nd. In all, 33 radioisotopes of Neodymium have been characterized up to now, with the most stable being naturally occurring isotopes 144Nd (alpha decay, a half-life (t1/2) of 2.29×1015 years) and 150Nd (double beta decay, t1/2 of 7×1018 years). All of the remaining radioactive isotopes have half-lives that are less than 11 days, and the majority of these have half-lives that are less than 70 seconds. This element also has 13 known meta states with the most stable being 139mNd (t1/2 5.5 hours), 135mNd (t1/2 5.5 minutes) and 133m1Nd (t1/2 ~70 seconds).The primary decay modes before the most abundant stable isotope, 142Nd, are electron capture and positron decay, and the primary mode after is beta decay. The primary decay products before 142Nd are element Pr (praseodymium) isotopes and the primary products after are element Pm (promethium) isotopes.

Naturally occurring erbium (68Er) is composed of 6 stable isotopes, 162Er, 164Er, 166Er, 167Er, 168Er, and 170Er with 166Er being the most abundant (33.503% natural abundance).

Naturally occurring ruthenium (44Ru) is composed of seven stable isotopes. Additionally, 27 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are 106Ru, with a half-life of 373.59 days; 103Ru, with a half-life of 39.26 days and 97Ru, with a half-life of 2.9 days.Twenty-four other radioisotopes have been characterized with atomic weights ranging from 86.95 u (87Ru) to 119.95 u (120Ru). Most of these have half-lives that are less than five minutes, excepting 95Ru (half-life: 1.643 hours) and 105Ru (half-life: 4.44 hours).The primary decay mode before the most abundant isotope, 102Ru, is electron capture and the primary mode after is beta emission. The primary decay product before 102Ru is technetium and the primary product after is rhodium.

Naturally occurring gadolinium (64Gd) is composed of 6 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and 1 radioisotope, 152Gd, with 158Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of 160Gd has never been observed; only lower limit on its half-life of more than 1.3×1021 years has been set experimentally.Thirty radioisotopes have been characterized, with the most stable being alpha-decaying 152Gd (naturally occurring) with a half-life of 1.08×1014 years, and 150Gd with a half-life of 1.79×106 years. All of the remaining radioactive isotopes have half-lives less than 74.7 years. The majority of these have half-lives less than 24.6 seconds. Gadolinium isotopes have 10 metastable isomers, with the most stable being 143mGd (t1/2=110 seconds), 145mGd (t1/2=85 seconds) and 141mGd (t1/2=24.5 seconds).The primary decay mode at atomic weights lower than the most abundant stable isotope, 158Gd, is electron capture, and the primary mode at higher atomic weights is beta decay. The primary decay products for isotopes of weights lower than 158Gd are the element Eu (europium) isotopes and the primary products at higher weights are the element Tb (terbium) isotopes.Gadolinium-153 has a half-life of 240.4±10 days and emits gamma radiation with strong peaks at 41 keV and 102 keV. It is used as a gamma ray source for X-ray absorptiometry and fluorescence, for bone density gauges for osteoporosis screening, and for radiometric profiling in the Lixiscope portable x-ray imaging system, also known as the Lixi Profiler. In nuclear medicine, it serves to calibrate the equipment needed like single-photon emission computed tomography systems (SPECT) to make x-rays. It ensures that the machines work correctly to produce images of radioisotope distribution inside the patient. This isotope is produced in a nuclear reactor from europium or enriched gadolinium. It can also detect the loss of calcium in the hip and back bones, allowing the ability to diagnose osteoporosis.Gadolinium-148 would be ideal for radioisotope thermoelectric generators due to its 74-year half life, high density, and dominant alpha decay mode. However, Gadolinium-148 cannot be economically synthesized in sufficient quantities to power a RTG.

Beryllium (4Be) has 12 known isotopes, but only one of these isotopes (9Be) is stable and a primordial nuclide. As such, beryllium is considered a monoisotopic element. It is also a mononuclidic element, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (standard atomic weight is 9.0122). Beryllium is unique as being the only monoisotopic element with both an even number of protons and an odd number of neutrons. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons.Of the 11 radioisotopes of beryllium, the most stable are 10Be with a half-life of 1.39 million years and 7Be with a half-life of 53.22 days. All other radioisotopes have half-lives under 13.85 seconds, most under 0.03 seconds. The least stable isotope is 6Be, with a half-life measured as 5.03 × 10−21 seconds.The natural light-element ratio of equal protons and neutron numbers is prevented in beryllium by the extreme instability of 8Be toward alpha decay, which is favored due to the extremely tight binding of 4He nuclei. The half-life for the decay of 8Be is only 6.7(17)×10−17 seconds.Beryllium is prevented from having a stable isotope with 4 protons and 6 neutrons by the very large mismatch in proton/neutron ratio for such a light element. Nevertheless, this isotope, 10Be, has a half-life of 1.39 million years, which indicates unusual stability for a light isotope with such a large neutron/proton imbalance. Still other possible beryllium isotopes have even more severe mismatches in neutron and proton number, and thus are even less stable.Most 9Be in the universe is thought to be formed by cosmic ray nucleosynthesis from cosmic ray spallation in the period between the Big Bang and the formation of the solar system. The isotopes 7Be, with a half-life of 53.22 days, and 10Be are both cosmogenic nuclides because they are made on a recent timescale in the solar system by spallation, like 14C. These two radioisotopes of beryllium in the atmosphere track the sun spot cycle and solar activity, since this affects the magnetic field that shields the Earth from cosmic rays. The rate at which the short-lived 7Be is transferred from the air to the ground is controlled in part by the weather. 7Be decay in the sun is one of the sources of solar neutrinos, and the first type ever detected using the Homestake experiment. Presence of 7Be in sediments is often used to establish that they are fresh, i.e. less than about 3–4 months in age, or about two half-lives of 7Be.

Thallium (81Tl) has 37 isotopes with atomic masses that range from 176 to 212. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years.

Naturally occurring cadmium (48Cd) is composed of 8 isotopes. For two of them, natural radioactivity was observed, and three others are predicted to be radioactive but their decays were never observed, due to extremely long half-life times. The two natural radioactive isotopes are 113Cd (beta decay, half-life is 8.04 × 1015 years) and 116Cd (two-neutrino double beta decay, half-life is 2.8 × 1019 years).

Aluminium (13Al) has 22 known isotopes from 21Al to 42Al and 4 known isomers. Only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2 × 105 y) occur naturally, however 27Al has a natural abundance of 99.9+ %. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. The standard atomic weight is 26.9815386(8). 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of sediment transport, deposition, and storage, as well as burial times, and erosion, on 105 to 106 year time scales.Cosmogenic aluminium-26 was first applied in studies of the Moon and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.

Lawrencium (103Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are twelve known radioisotopes from 252Lr to 266Lr, and 1 isomer (253mLr). The longest-lived isotope is 266Lr with a half-life of 11 hours. Heavier isotopes are expected to have longer half-lives.

Uranium (92U) is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes (uranium-238 and uranium-235) that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The standard atomic weight of natural uranium is 238.02891(3).

There are 39 known isotopes of radon (86Rn) from 193Rn to 231Rn; all are radioactive. The most stable isotope is 222Rn with a half-life of 3.823 days. Four isotopes, 218, 219, 220, 222Rn occur in trace quantities in nature as decay products of, respectively, 218At, 223Ra, 224Ra, and 226Ra. 218Rn and 222Rn are intermediate steps in the decay chain for 238U, 219Rn is an intermediate step in the decay chain for 235U and 220Rn occurs in the decay chain for 232Th.

Naturally occurring zirconium (40Zr) is composed of four stable isotopes (of which one may in the future be found radioactive), and one very long-lived radioisotope (96Zr), a primordial nuclide that decays via double beta decay with an observed half-life of 2.0×1019 years; it can also undergo single beta decay, which is not yet observed, but the theoretically predicted value of t1/2 is 2.4×1020 years. The second most stable radioisotope is 93Zr, which has a half-life of 1.53 million years. Twenty-seven other radioisotopes have been observed. All have half-lives less than a day except for 95Zr (64.02 days), 88Zr (63.4 days), and 89Zr (78.41 hours). The primary decay mode is electron capture for isotopes lighter than 92Zr, and the primary mode for heavier isotopes is beta decay.Zirconium is the heaviest element that can be formed from symmetric fusion, from either 45Sc, or 46Ca producing 90Zr (after two beta-plus decays from 90Mo) and 92Zr respectively. All heavier elements are formed either through asymmetric fusion or during the collapse of supernovae. As most of these are energy-absorbing processes, most nuclides of elements heavier than zirconium are theoretically unstable to spontaneous fission, although in many cases, the half-life for this is too long to have been observed. See list of nuclides for a tabulation.

Template:Infobox neodynium isotopes Naturally occurring neodymium (60Nd) is composed of 5 stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% natural abundance), and 2 long-lived radioisotopes, 144Nd and 150Nd. In all, 33 radioisotopes of Neodymium have been characterized up to now, with the most stable being naturally occurring isotopes 144Nd (alpha decay, a half-life (t1/2) of 2.29×1015 years) and 150Nd (double beta decay, t1/2 of 7×1018 years).

Astatine (85At) has 37 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 229. There also exist 23 metastable excited states. The longest-lived isotope is 210At, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is 219At with a half-life of 56 seconds.There are 32 known isotopes of astatine, with atomic masses (mass numbers) of 191 and 193–223.

Naturally occurring praseodymium (59Pr) is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr, with a half-life of 13.57 days and 142Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours and the majority of these have half-lives that are less than 33 seconds. This element also has 15 meta states with the most stable being 138mPr (t1/2 2.12 hours), 142mPr (t1/2 14.6 minutes) and 134mPr (t1/2 11 minutes).The isotopes of praseodymium range in atomic weight from 120.955 u (121Pr) to 158.955 u (159Pr). The primary decay mode before the stable isotope, 141Pr, is electron capture and the mode after is beta decay. The primary decay products before 141Pr are element 58 (cerium) isotopes and the primary products after are element 60 (neodymium) isotopes.

Naturally occurring niobium (41Nb), element 41, is composed of one stable isotope (93Nb). 93Nb is the lightest nuclide theoretically susceptible to spontaneous fission, and although this has never been observed, it makes niobium theoretically the lightest element with no stable isotope. The first 40 elements (to zirconium) all have at least one stable nuclide susceptible in theory only to proton decay.The most stable radioisotope is 92Nb with a half-life of 34.7 million years. This nuclide is the longest-lived radionuclide of all elements that has not yet been detected in nature as a primordial isotope. (The nuclide with the next longest half-life, 146Sm with half-life 68 million years, has been detected, and is thus primordial).The next longest-lived niobium nuclides are 94Nb (half-life: 20,300 years), and 91Nb with a half-life of 680 years. There is also a meta state at 31 keV whose half-life is 16.13 years. Twenty three other radioisotopes have been characterized. Most of these have half-lives that are less than two hours except 95Nb (35 days), 96Nb (23.4 hours) and 90Nb (14.6 hours). The primary decay mode before the stable 93Nb is electron capture and the primary mode after is beta emission with some neutron emission occurring in 104–110Nb.Only 95Nb (35 days) and 97Nb (72 minutes) and heavier isotopes (half-lives in seconds) are fission products in significant quantity, as the other isotopes are shadowed by stable or very long-lived (93Zr) isotopes of the preceding element zirconium from production via beta decay of neutron-rich fission fragments. 95Nb is the decay product of 95Zr (64 days), so disappearance of 95Nb in used nuclear fuel is slower than would be expected from its own 35-day halflife alone. Tiny amounts of the other isotopes may be produced as direct fission products.

Promethium (61Pm) has no stable isotopes, and does not exist in nature, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu. It is a synthetic element, first produced in 1945. Thirty-eight radioisotopes have been characterized, with the most stable being 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years.

A medical isotope is an isotope used in medicine.The first uses of isotopes in medicine were in radiopharmaceuticals, and this is still the most common use. However more recently, separated stable isotopes have also come into use.Examples of non-radioactive medical isotopes are:Deuterium in deuterated drugsCarbon-13 used in liver function and metabolic tests

Thallium (81Tl) has 37 isotopes with atomic masses that range from 176 to 212. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years. 207Tl, with a half-life of 4.77 minutes, has the longest half-life of naturally occurring radioisotopes.Thallium-202 (half-life 12.23 days) can be made in a cyclotron while thallium-204 (half-life 3.78 years) is made by the neutron activation of stable thallium in a nuclear reactor.In the fully ionized state, the isotope 205Tl becomes beta-radioactive, decaying to 205Pb, but 203Tl remains stable.

Silicon (14Si) has 24 known isotopes, with mass numbers ranging from 22 to 45. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years (0.21 MeV), and it decays by beta emission to 32P (which has a 14.28 day half-life [1]) and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes.

The alkaline earth metal strontium (38Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). It's standard atomic weight is 87.62(1).Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years (i.e. more than three times longer than the current age of the universe).

Naturally occurring silver (47Ag) is composed of the two stable isotopes 107Ag and 109Ag with 107Ag being the more abundant (51.839% natural abundance).

Aluminium (13Al) has 22 known isotopes from 21Al to 42Al and 4 known isomers. Only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2 × 105 y) occur naturally, however 27Al has a natural abundance of 99.9+ %. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. The standard atomic weight is 26.9815386(8). 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons.

Astatine (85At) has 37 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 229. There also exist 23 metastable excited states. The longest-lived isotope is 210At, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is 219At with a half-life of 56 seconds.There are 32 known isotopes of astatine, with atomic masses (mass numbers) of 191 and 193–223. No stable or even long-lived astatine isotope is known, and no such isotope is expected to exist.

Americium (Am) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no known stable isotopes. The first isotope to be synthesized was 241Am in 1944. The artificial element decays into alpha particles. Americium has an atomic number of 95 (the number of protons in the nucleus of the americium atom).Nineteen radioisotopes of americium have been characterized, with the most stable being 243Am with a half-life of 7,370 years, and 241Am with a half-life of 432.2 years. All of the remaining radioactive isotopes have half-lives that are less than 51 hours, and the majority of these have half-lives that are less than 100 minutes. This element also has 8 meta states, with the most stable being 242mAm (t1/2 141 years). The isotopes of americium range in atomic weight from 231.046 u (231Am) to 249.078 u (249Am).

Naturally occurring cobalt (27Co) is composed of 1 stable isotope, 59Co. 28 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.8 days, 56Co with a half-life of 77.27 days, and 58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second. This element also has 11 meta states, all of which have half-lives less than 15 minutes.The isotopes of cobalt range in atomic weight from 47Co to 75Co. The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope, 59Co, is electron capture and the primary mode of decay for those of greater than 59 atomic mass units is beta decay. The primary decay products before 59Co are iron isotopes and the primary products after are nickel isotopes.Radioactive isotopes can be produced by various nuclear reactions. For example, the isotope 57Co is produced by cyclotron irradiation of iron. The principal reaction involved is the (d,n) reaction 56Fe + 2H → n + 57Co.

Beryllium (4Be) has 12 known isotopes, but only one of these isotopes (9Be) is stable and a primordial nuclide. As such, beryllium is considered a monoisotopic element. It is also a mononuclidic element, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (standard atomic weight is 9.0122). Beryllium is unique as being the only monoisotopic element with both an even number of protons and an odd number of neutrons.

Neptunium (Np) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 239Np in 1940, produced by bombarding 238U with neutrons to produce 239U, which then underwent beta decay to 239Np.Trace quantities are found in nature from neutron capture by uranium atoms.Twenty neptunium radioisotopes have been characterized, with the most stable being 237Np with a half-life of 2.14 million years, 236Np with a half-life of 154,000 years, and 235Np with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lives that are less than 4.5 days, and the majority of these have half-lives that are less than 50 minutes. This element also has 4 meta states, with the most stable being 236mNp (t1/2 22.5 hours).The isotopes of neptunium range in atomic weight from 225.0339 u (225Np) to 244.068 u (244Np). The primary decay mode before the most stable isotope, 237Np, is electron capture (with a good deal of alpha emission), and the primary mode after is beta emission. The primary decay products before 237Np are isotopes of uranium and protactinium, and the primary products after are isotopes of plutonium. Uranium-237 and Neptunium-239 are regarded as the leading hazardous radioisotopes in the first hour-to-week period following nuclear fallout from a nuclear detonation, with Np-239 dominating "the spectrum for several days".

There are two natural isotopes of iridium (77Ir), and 34 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years. All other isomers have half-lives under a year, most under a day.

Naturally occurring palladium (46Pd) is composed of six stable isotopes, 102Pd, 104Pd, 105Pd, 106Pd, 108Pd, and 110Pd, although two of them are theoretically unstable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with a half-life of 17 days, and 100Pd with a half-life of 3.63 days. Twenty-three other radioisotopes have been characterized with atomic weights ranging from 90.949 u (91Pd) to 123.937 u (124Pd).

Potassium (19K) has 24 known isotopes from 32K to 56K. Three isotopes occur naturally: stable 39K (93.3%) and 41K (6.7%), and the long-lived radioisotope 40K (0.012%).Naturally occurring radioactive 40K decays to stable 40Ar (10.72% of decays) by electron capture or positron emission (giving it the longest known positron-emitter nuclide half-life). Alternately, and most of the time (89.28%), it decays to stable 40Ca by beta decay. 40K has a half-life of 1.248×109 years. The long half life of this primordial radioisotope is caused by a highly spin-forbidden transition: 40K has a nuclear spin of 4, while both of its decay daughters are even-even isotopes with spins of 0.40K occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C. In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second.The decay of 40K to 40Ar enables a commonly used method for dating rocks. The conventional K-Ar dating method depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon (i.e., 40Ar) was quantitatively retained. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40Ar that has accumulated.All other potassium isotopes have half-lives under a day, most under a minute. The least stable are 33K and 34K, both with half-lives shorter than 25 nanoseconds. The half-life of 32K is unknown.Outside of its use in dating 40K has been used extensively as tracers in studies of weathering. Various potassium isotopes also been used for nutrient cycling studies because potassium is a macronutrient required for life.

Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm (half life: 1.06×1011 y) and 148Sm (7×1015 y), with 152Sm being the most abundant (26.75% natural abundance). 146Sm is also fairly long-lived (6.8×107 y), but is not long-lived enough to have survived from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System.Other than the naturally occurring isotopes, the longest-lived radioisotopes are 151Sm, which has a half-life of 88.8 years, and 145Sm, which has a half-life of 340 days. All of the remaining radioisotopes have half-lives that are less than two days, and the majority of these have half-lives that are less than 48 seconds. This element also has twelve known isomers with the most stable being 141mSm (t1/2 22.6 minutes), 143m1Sm (t1/2 66 seconds) and 139mSm (t1/2 10.7 seconds).The long lived isotopes,146Sm, 147Sm, and 148Sm primarily decay by alpha decay to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones decay by beta decay to isotopes of europium.Isotopes of samarium are used in samarium-neodymium dating for determining the age relationships of rocks and meteorites.151Sm is a medium-lived fission product and acts as a neutron poison in the nuclear fuel cycle. The stable fission product 149Sm is also a neutron poison.

Fermium (100Fm) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in fallout from nuclear testing) was 255Fm in 1952. 250Fm was independently synthesized shortly after the discovery of 255Fm. There are 20 known radioisotopes ranging in atomic mass from 241Fm to 260Fm (260Fm is unconfirmed), and 2 nuclear isomers, 250mFm and 251mFm. The longest-lived isotope is 257Fm with a half-life of 100.5 days, and the longest-lived isomer is 250mFm with a half-life of 1.8 seconds.

Naturally occurring palladium (46Pd) is composed of six stable isotopes, 102Pd, 104Pd, 105Pd, 106Pd, 108Pd, and 110Pd, although two of them are theoretically unstable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with a half-life of 17 days, and 100Pd with a half-life of 3.63 days. Twenty-three other radioisotopes have been characterized with atomic weights ranging from 90.949 u (91Pd) to 123.937 u (124Pd). Most of these have half-lives that are less than a half an hour except 101Pd (half-life: 8.47 hours), 109Pd (half-life: 13.7 hours), and 112Pd (half-life: 21 hours).The primary decay mode before the most abundant stable isotope, 106Pd, is electron capture and the primary mode after is beta decay. The primary decay product before 106Pd is rhodium and the primary product after is silver.Radiogenic 107Ag is a decay product of 107Pd and was first discovered in the Santa Clara meteorite of 1978. The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus Ag correlations observed in bodies, which have clearly been melted since accretion of the solar system, must reflect the presence of short-lived nuclides in the early solar system.

Naturally occurring nickel (28Ni) is composed of five stable isotopes; 58Ni, 60Ni, 61Ni, 62Ni and 64Ni with 58Ni being the most abundant (68.077% natural abundance). 26 radioisotopes have been characterised with the most stable being 59Ni with a half-life of 76,000 years, 63Ni with a half-life of 100.1 years, and 56Ni with a half-life of 6.077 days.

Chlorine (17Cl) has 24 isotopes with mass numbers ranging from 28Cl to 51Cl and 2 isomers (34mCl and 38mCl). There are two principal stable isotopes, 35Cl (75.78%) and 37Cl (24.22%), giving chlorine a standard atomic weight of 35.45. The longest-lived radioactive isotope is 36Cl, which has a half-life of 301,000 years. All other isotopes have half-lives under 1 hour, many less than one second.

Indium (49In) consists of two primordial nuclides, with the most common (~ 95.7%) nuclide (115In) being measurably though weakly radioactive. Its spin-forbidden decay has a half life of 441 trillion years.The stable isotope 113In is only 4.3% of naturally occurring indium. Among elements with a known stable isotope, only tellurium and rhenium similarly occur with a stable isotope in lower abundance than the long-lived radioactive isotope. Other than 115In, the longest-lived radioisotope is 111In, with a half-life of 2.8047 days. All other radioisotopes have half-lives less than a day. This element also has 47 isomers, the longest-lived being 114m1In, with a half-life of 49.51 days. All other meta-states have half-lives less than a day, most less than an hour, and many measured in milliseconds or less.Indium-111 is used medically in nuclear imaging, as a radiotracer nuclide tag for gamma camera localization of protein radiopharmaceuticals, such as In-111-labeled octreotide, which binds to receptors on certain endocrine tumors (Octreoscan). Indium-111 is also used in indium white blood cell scans, which use nuclear medical techniques to search for hidden infections.

if you want a list with just one giant list of isotopes, see Isotope lists, all.

There are 38 known isotopes and 17 nuclear isomers of tellurium (52Te), with atomic masses that range from 105 to 142. These are listed in the table below.Naturally-occurring tellurium on Earth consists of eight isotopes. Two of these have been found to be radioactive: 128Te and 130Te undergo double beta decay with half-lives of, respectively, 2.2×1024 (2.2 septillion) years (the longest half-life of all nuclides proven to be radioactive) and 7.9×1020 (790 quintillion) years.

Naturally occurring tungsten (74W) consists of five isotopes. Four are considered stable (182W, 183W, 184W, and 186W) and one is slightly radioactive, 180W, with an extremely long half-life of 1.8 ± 0.2 Ea (1018 years). On average, two alpha decays of 180W occur per gram of natural tungsten per year so for most practical purposes tungsten can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so. The other naturally occurring isotopes have not been observed to decay, and lower bounds for their half lives have been established:182W, t1/2 > 7.7×1021 years183W, t1/2 > 4.1×1021 years184W, t1/2 > 8.9×1021 years186W, t1/2 > 8.2×1021 yearsThirty-three artificial radioisotopes of tungsten have been characterized with mass numbers ranging from 157 to 194, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days and 178W with a half-life of 21.6 days. All of the remaining radioactive isotopes have half-lives of less than 24 hours, and most of these have half-lives that are less than 8 minutes. Tungsten also has 11 meta states with mass numbers of 158, 179, with 3, 180, with 2, 183, 185, 186, with 2, and 190, the most stable being 179m1W (t1/2 6.4 minutes).

There are 38 known isotopes and 17 nuclear isomers of tellurium (52Te), with atomic masses that range from 105 to 142. These are listed in the table below.Naturally-occurring tellurium on Earth consists of eight isotopes. Two of these have been found to be radioactive: 128Te and 130Te undergo double beta decay with half-lives of, respectively, 2.2×1024 (2.2 septillion) years (the longest half-life of all nuclides proven to be radioactive) and 7.9×1020 (790 quintillion) years. The longest-lived artificial radioisotope of Tellerium is 121Te with a half-life of nearly 19 days. Several nuclear isomers have longer half-lives, the longest being 121mTe with a half-life of 154 days.The very-long-lived radioisotopes 128Te and 130Te are the two most common isotopes of tellurium. Of elements with at least one stable isotope, only indium and rhenium likewise have a radioisotope in greater abundance than a stable one.It has been claimed that electron capture of 123Te was observed, but the recent measurements of the same team have disproved this. The half-life of 123Te is longer than 9.2 × 1016 years, and probably much longer.124Te can be used as a starting material in the production of radionuclides by a cyclotron or other particle accelerators. Some common radionuclides that can be produced from tellurium-124 are iodine-123 and iodine-124.The short-lived isotope 135Te (half-life 19 seconds) is produced as a fission product in nuclear reactors. It decays, via two beta decays, to 135Xe, the most powerful known neutron absorber, and the cause of the iodine pit phenomenon.With the exception of beryllium, tellurium is the lightest element observed to commonly undergo alpha decay, with isotopes 106Te to 110Te being seen to undergo this mode of decay. Some lighter elements have isotopes with alpha decay as a rare branch.

Meitnerium (109Mt) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 266Mt in 1982 (this is also the only isotope directly synthesized, all other isotopes are decay products of heavier elements). There are eight known isotopes, from 266Mt to 278Mt. There may also be two isomers. The longest-lived of the known isotopes is 278Mt with a half-life of 8 seconds. The unconfirmed heavier 282Mt appears to have an even longer half-ife of 67 seconds.

Sulfur (16S) has 24 known isotopes with mass numbers ranging from 26 to 49, four of which are stable: 32S (95.02%), 33S (0.75%), 34S (4.21%), and 36S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium nuclei, in the so-called alpha process of exploding type II supernovae (see silicon burning).Other than 35S, the radioactive isotopes of sulphur are all comparatively short-lived. 35S is formed from cosmic ray spallation of 40Ar in the atmosphere. It has a half-life of 87 days. The next longest-lived radioisotope is sulfur-38, with a half-life of 17 minutes. The shortest-lived is 49S, with a half-life shorter than 200 nanoseconds.When sulfide minerals are precipitated, isotopic equilibration among solids and liquid may cause small differences in the δS-64 values of co-genetic minerals. The differences between minerals can be used to estimate the temperature of equilibration. The δC-13 and δS-34 of coexisting carbonates and sulfides can be used to determine the pH and oxygen fugacity of the ore-bearing fluid during ore formation.In most forest ecosystems, sulfate is derived mostly from the atmosphere; weathering of ore minerals and evaporites also contribute some sulfur. Sulfur with a distinctive isotopic composition has been used to identify pollution sources, and enriched sulfur has been added as a tracer in hydrologic studies. Differences in the natural abundances can also be used in systems where there is sufficient variation in the 34S of ecosystem components. Rocky Mountain lakes thought to be dominated by atmospheric sources of sulfate have been found to have different δS-34 values from oceans believed to be dominated by watershed sources of sulfate.

Curium (Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutrons. All of the isotopes are radioactive.There are 21 known radioisotopes with atomic masses ranging from 232Cm to 252Cm. There are also four known nuclear isomers (243mCm, 244mCm, 245mCm, and 249mCm). The longest-lived isotope is 247Cm, with a half-life of 15.6 million years – several orders of magnitude longer than the half-life of all known nuclei of elements beyond curium in the periodic table. The shortest-lived isomer is 244mCm with a half-life of 34 milliseconds.

There are seven stable isotopes of mercury (80Hg) with 202Hg being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining 32 radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spins of 1/2 and 3/2 respectively.Mercury-180, producible from thallium-180, was found in 2010 to be capable of an unusual form of spontaneous fission. The fission products are krypton-80 and ruthenium-100.

Although thorium (Th), with atomic number 90, has 6 naturally occurring isotopes, none of these isotopes are stable; however, one isotope, 232Th, is relatively stable, with a half-life of 14.05 billion years, considerably longer than the age of the earth, and even slightly longer than the generally accepted age of the universe. This isotope makes up nearly all natural thorium. As such, thorium is considered to be mononuclidic. It has a characteristic terrestrial isotopic composition and thus an atomic mass can be given.Thirty radioisotopes have been characterized, with the most stable (after 232Th) being 230Th with a half-life of 75,380 years, 229Th with a half-life of 7,340 years, and 228Th with a half-life of 1.92 years. All of the remaining radioactive isotopes have half-lives that are less than thirty days and the majority of these have half-lives that are less than ten minutes. One isotope, 229Th, has a nuclear isomer (or metastable state) with a remarkably low excitation energy, recently measured to be 7.6 ± 0.5 eV.The known isotopes of thorium range in mass number from 209 to 238.

Naturally occurring erbium (68Er) is composed of 6 stable isotopes, 162Er, 164Er, 166Er, 167Er, 168Er, and 170Er with 166Er being the most abundant (33.503% natural abundance). Thirty radioisotopes have been characterized with between 74 and 108 neutrons, or 142 to 177 nucleons, with the most stable being 169Er with a half-life of 9.4 days, 172Er with a half-life of 49.3 hours, 160Er with a half-life of 28.58 hours, 165Er with a half-life of 10.36 hours, and 171Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has 13 meta states, with the most stable being 167mEr (t1/2 2.269 seconds).The isotopes of erbium range in atomic weight from 141.9723 u (142Er) to 176.9541 u (177Er). The primary decay mode before the most abundant stable isotope, 166Er, is electron capture, and the primary mode after is beta decay. The primary decay products before 166Er are holmium isotopes, and the primary products after are thulium isotopes.

Naturally occurring gadolinium (64Gd) is composed of 6 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and 1 radioisotope, 152Gd, with 158Gd being the most abundant (24.84% natural abundance).

Naturally occurring Ytterbium (70Yb) is composed of 7 stable isotopes, 168Yb, 170Yb, 171Yb, 172Yb, 173Yb, 174Yb, and 176Yb, with 174Yb being the most abundant (31.83% natural abundance). Twenty-seven radioisotopes have been characterized, with the most stable being 169Yb with a half-life of 32.026 days, 175Yb with a half-life of 4.185 days, and 166Yb with a half-life of 56.7 hours.

Natural gallium (31Ga) consists of a mixture of two stable isotopes: gallium-69 and gallium-71. The most commercially important radioisotopes are gallium-67 and gallium-68.Gallium-67 (half-life 3.3 days) is a gamma-emitting isotope (the gamma emitted immediately after electron-capture) used in standard nuclear medical imaging, in procedures usually referred to as gallium scans. It is usually used as the free ion, Ga3+. It is the longest-lived radioisotope of gallium.The shorter-lived gallium-68 (half-life 68 minutes) is a positron-emitting isotope generated from germanium-68 in gallium-68 generators, for use in a small minority of diagnostic PET scans. For this use, it is usually attached as a tracer to a carrier molecule, which gives the resulting radiopharmaceutical a different tissue-uptake specificity from the ionic Ga-67 radioisotope normally used in standard gallium scans.

Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm (half life: 1.06×1011 y) and 148Sm (7×1015 y), with 152Sm being the most abundant (26.75% natural abundance).

Caesium (55Cs) or cesium as it is spelled in the United States has 40 known isotopes, making it, along with barium and mercury, the element with the most isotopes. The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.Beginning in 1945 with the commencement of nuclear testing, caesium isotopes were released into the atmosphere where it is absorbed readily into solution and is returned to the surface of the earth as a component of radioactive fallout. Once caesium enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes can be estimated as a function of time.

Naturally occurring scandium (21Sc) is composed of one stable isotope 45Sc. Twenty-four radioisotopes have been characterized with the most stable being 46Sc with a half-life of 83.8 days, 47Sc with a half-life of 3.35 days, and 48Sc with a half-life of 43.7 hours and Sc-44 with a half-life of 3.97 hours. All of the remaining radioactive isotopes have half-lives that are less than four hours, and the majority of these have half-lives that are less than two minutes, the least stable being 39Sc with a half-life shorter than 300 nanoseconds. The half-lives for isotopes with mass numbers less than 39 is unknown. This element also has 10 meta states with the most stable being 44mSc (t1/2 58.6 h).The isotopes of scandium range in atomic weight from 36 u (36Sc) to 60 u (60Sc). The primary decay mode at masses lower than the only stable isotope, 45Sc, is Beta-plus or electron capture, and the primary mode at masses above it is beta-minus. The primary decay products at atomic weights below 45Sc are calcium isotopes and the primary products from higher atomic weights are titanium isotopes.

Natural gallium (31Ga) consists of a mixture of two stable isotopes: gallium-69 and gallium-71. The most commercially important radioisotopes are gallium-67 and gallium-68.Gallium-67 (half-life 3.3 days) is a gamma-emitting isotope (the gamma emitted immediately after electron-capture) used in standard nuclear medical imaging, in procedures usually referred to as gallium scans. It is usually used as the free ion, Ga3+.

Naturally occurring dysprosium (Dy) is composed of 7 stable isotopes, 156Dy, 158Dy, 160Dy, 161Dy, 162Dy, 163Dy and 164Dy, with 164Dy being the most abundant (28.18% natural abundance). Twenty-nine radioisotopes have been characterized, with the most stable being 154Dy with a half-life of 3.0 million years, 159Dy with a half-life of 144.4 days, and 166Dy with a half-life of 81.6 hours. All of the remaining radioactive isotopes have half-lives that are less than 10 hours, and the majority of these have half-lives that are less than 30 seconds. This element also has 12 meta states, with the most stable being 165mDy (t1/2 1.257 minutes), 147mDy (t1/2 55.7 seconds) and 145mDy (t1/2 13.6 seconds).The primary decay mode before the most abundant stable isotope, 164Dy, is electron capture, and the primary mode after is beta decay. The primary decay products before 164Dy are terbium isotopes, and the primary products after are holmium isotopes.

Naturally occurring titanium (22Ti) is composed of 5 stable isotopes; 46Ti, 47Ti, 48Ti, 49Ti and 50Ti with 48Ti being the most abundant (73.8% natural abundance). Twenty-one radioisotopes have been characterized, with the most stable being 44Ti with a half-life of 60 years, 45Ti with a half-life of 184.8 minutes, 51Ti with a half-life of 5.76 minutes, and 52Ti with a half-life of 1.7 minutes.

Uranium (92U) is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes (uranium-238 and uranium-235) that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The standard atomic weight of natural uranium is 238.02891(3). Other isotopes such as uranium-232 have been produced in breeder reactors.Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.2739–99.2752% natural abundance), uranium-235 (0.7198–0.7202%), and uranium-234 (0.0050–0.0059%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of 4.4683×109 years (close to the age of the Earth).Uranium-238 is an α emitter, decaying through the 18-member uranium series into lead-206. The decay series of uranium-235 (historically called actino-uranium) has 15 members that ends in lead-207. The constant rates of decay in these series makes comparison of the ratios of parent to daughter elements useful in radiometric dating. Uranium-233 is made from thorium-232 by neutron bombardment.The isotope uranium-235 is important for both nuclear reactors and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile, that is, can be broken apart by thermal neutrons. The isotope uranium-238 is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium-239, which also is fissile.

Protactinium (91Pa) has no stable isotopes. There are three naturally occurring isotopes, allowing a standard mass to be given.Twenty-nine radioisotopes of protactinium have been characterized, with the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 26.967 days, and 230Pa with a half-life of 17.4 days. All of the remaining radioactive isotopes have half-lives that are less than 1.6 days, and the majority of these have half-lives that are less than 1.8 seconds. This element also has 3 meta states, 217mPa (t1/2 1.15 milliseconds), 229mPa (t1/2 420 nanoseconds), and 234mPa (t1/2 1.17 minutes).The only naturally occurring isotopes are 231Pa, which occurs as an intermediate decay product of 235U, 234Pa and 234mPa, both of which occur as intermediate decay products of 238U. 231Pa makes up nearly all natural protactinium.The primary decay mode for isotopes of Pa lighter than (and including) the most stable isotope 231Pa is alpha decay, except for 228Pa to 230Pa, which primarily decay by electron capture to isotopes of thorium. The primary mode for the heavier isotopes is beta minus (β−) decay. The primary decay products of 231Pa and isotopes of protactinium lighter than and including 227Pa are isotopes of actinium and the primary decay products for the heavier isotopes of protactinium are isotopes of uranium.

Rubidium (37Rb) has 32 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%). Normal mixes of rubidium are radioactive enough to fog photographic film in approximately 30 to 60 days.87Rb has a half-life of 4.92×1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. 87Rb has been used extensively in dating rocks; 87Rb decays to stable strontium-87 by emission of a negative beta particle, i.e. an electron ejected from the nucleus. During fractional crystallization, Sr tends to become concentrated in plagioclase, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual magma may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. Highest ratios (10 or higher) occur in pegmatites. If the initial amount of Sr is known or can be extrapolated, the age can be determined by measurement of the Rb and Sr concentrations and the 87Sr/86Sr ratio. The dates indicate the true age of the minerals only if the rocks have not been subsequently altered. See rubidium-strontium dating for a more detailed discussion.Other than 87Rb, the longest-lived radioisotopes are 83Rb with a half-life of 86.2 days, 84Rb with a half-life of 33.1 days and 86Rb with a half-life of 18.642 days. All other radioisotopes have half-lives less than a day.82Rb is used in some cardiac PET scans to assess myocardial perfusion. It has a half-life of 1.273 minutes. It does not exist naturally, but can be made from the decay of 82Sr.

Naturally occurring lutetium (71Lu) is composed of 1 stable isotope 175Lu (97.41% natural abundance) and one long-lived radioisotope, 176Lu with a half-life of 3.78 × 1010 years (2.59% natural abundance). Thirty-four radioisotopes have been characterized, with the most stable, besides 176Lu, being 174Lu with a half-life of 3.31 years, and 173Lu with a half-life of 1.37 years. All of the remaining radioactive isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than half an hour. This element also has 18 meta states, with the most stable being 177mLu (t1/2 160.4 days), 174mLu (t1/2 142 days) and 178mLu (t1/2 23.1 minutes).The isotopes of lutetium range in atomic weight from 149.973 (150Lu) to 183.961 (184Lu). The primary decay mode before the most abundant stable isotope, 175Lu, is electron capture (with some alpha and positron emission), and the primary mode after is beta emission. The primary decay products before 175Lu are isotopes of ytterbium and the primary products after are isotopes of hafnium.

Naturally occurring rhodium (45Rh) is composed of only one stable isotope, 103Rh. The most stable radioisotopes are 101Rh with a half-life of 3.3 years, 102Rh with a half-life of 207 days, and 99Rh with a half-life of 16.1 days. Thirty other radioisotopes have been characterized with atomic weights ranging from 88.949 u (89Rh) to 121.943 u (122Rh). Most of these have half-lifes that are less than an hour except 100Rh (half-life: 20.8 hours) and 105Rh (half-life: 35.36 hours). There are also numerous meta states with the most stable being 102mRh (0.141 MeV) with a half-life of about 3.7 years and 101mRh (0.157 MeV) with a half-life of 4.34 days.The primary decay mode before the only stable isotope, 103Rh, is electron capture and the primary mode after is beta emission. The primary decay product before 103Rh is ruthenium and the primary product after is palladium.

Naturally occurring lithium (3Li, standard atomic weight: [6.938, 6.997], conventional: 6.94) is composed of two stable isotopes, lithium-6 and lithium-7, with the latter being far more abundant: about 92.5 percent of the atoms. Both of the natural isotopes have an unexpectedly low nuclear binding energy per nucleon (~5.3 MeV) when compared with the adjacent lighter and heavier elements, helium (~7.1 MeV) and beryllium (~6.5 MeV).

Boron (5B) naturally occurs as isotopes 10B and 11B, the latter of which makes up about 80% of natural boron. There are 14 radioisotopes that have been discovered, with mass numbers from 6 to 21, all with short half-lives, the longest being that of 8B, with a half-life of only 770 milliseconds (ms) and 12B with a half-life of 20.2 ms. All other isotopes have half-lives shorter than 17.35 ms, with the least stable isotope being 7B, with a half-life of 150 yoctoseconds (ys).

Argon (18Ar) has 24 known isotopes, from 30Ar to 53Ar and 1 isomer (32mAr), three of which are stable, 36Ar, 38Ar, and 40Ar. On the Earth, 40Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are 39Ar with a half-life of 269 years, 42Ar with a half-life of 32.9 years, and 37Ar with a half-life of 35.04 days. All other isotopes have half-lives less than two hours, and most less than one minute.

There are twenty recognized isotopes of sodium (11Na), ranging from 18Na to 37Na and two isomers (22mNa and 24mNa). 23Na is the only stable (and the only primordial) isotope. As such, it is considered a monoisotopic element and it has a standard atomic weight of 22.98976928(2). Sodium has two radioactive cosmogenic isotopes (22Na, half-life = 2.605 years; and 24Na, half-life ≈ 15 hours). With the exception of those two, all other isotopes have half-lives under a minute, most under a second.

Isotope lists, 0-24 if you want a list with just one giant list of isotopes, see Isotope lists, all.

Naturally occurring chromium (24Cr) is composed of four stable isotopes; 50Cr, 52Cr, 53Cr, and 54Cr with 52Cr being the most abundant (83.789% natural abundance). 50Cr is suspected of decaying by β+β+ to 50Ti with a half-life of (more than) 1.8x1017 years. Twenty-two radioisotopes, all of which are entirely synthetic, have been characterized with the most stable being 51Cr with a half-life of 27.7 days.

Naturally occurring zinc (30Zn) is composed of the 5 stable isotopes 64Zn, 66Zn, 67Zn, 68Zn, and 70Zn with 64Zn being the most abundant (48.6% natural abundance). Twenty-five radioisotopes have been characterised with the most abundant and stable being 65Zn with a half-life of 244.26 days, and 72Zn with a half-life of 46.5 hours. All of the remaining radioactive isotopes have half-lives that are less than 14 hours and the majority of these have half-lives that are less than 1 second. This element also has 10 meta states.Zinc has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of isotopically enriched 64Zn, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 65Zn with a half-life of 244 days and produce approximately 1.115 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several days. Such a weapon is not known to have ever been built, tested, or used.

Naturally occurring ruthenium (44Ru) is composed of seven stable isotopes. Additionally, 27 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are 106Ru, with a half-life of 373.59 days; 103Ru, with a half-life of 39.26 days and 97Ru, with a half-life of 2.9 days.Twenty-four other radioisotopes have been characterized with atomic weights ranging from 86.95 u (87Ru) to 119.95 u (120Ru).

Naturally occurring vanadium (23V) is composed of one stable isotope 51V and one radioactive isotope 50V with a half-life of 1.5×1017 years. 24 artificial radioisotopes have been characterized (in the range of mass number between 40 and 65) with the most stable being 49V with a half-life of 330 days, and 48V with a half-life of 15.9735 days.

Isotope lists, all

Naturally occurring zinc (30Zn) is composed of the 5 stable isotopes 64Zn, 66Zn, 67Zn, 68Zn, and 70Zn with 64Zn being the most abundant (48.6% natural abundance). Twenty-five radioisotopes have been characterised with the most abundant and stable being 65Zn with a half-life of 244.26 days, and 72Zn with a half-life of 46.5 hours. All of the remaining radioactive isotopes have half-lives that are less than 14 hours and the majority of these have half-lives that are less than 1 second.

Naturally occurring europium (63Eu) is composed of 2 isotopes, 151Eu and 153Eu, with 153Eu being the most abundant (52.2% natural abundance). While 153Eu is observationally stable, 151Eu was recently found to be unstable and to undergo alpha decay. The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 y which corresponds to 1 alpha decay per two minutes in every kilogram of natural europium.

Mendelevium (101Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 256Md (which was also the first isotope of any element produced one atom at a time) in 1955. There are 16 known radioisotopes, ranging in atomic mass from 245Md to 260Md, and 5 isomers.

Naturally occurring rhodium (45Rh) is composed of only one stable isotope, 103Rh. The most stable radioisotopes are 101Rh with a half-life of 3.3 years, 102Rh with a half-life of 207 days, and 99Rh with a half-life of 16.1 days. Thirty other radioisotopes have been characterized with atomic weights ranging from 88.949 u (89Rh) to 121.943 u (122Rh). Most of these have half-lifes that are less than an hour except 100Rh (half-life: 20.8 hours) and 105Rh (half-life: 35.36 hours).