Isotopes of osmium
Encyclopedia
Osmium
(Os) has seven naturally occurring isotope
s, 6 of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other one, 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/187Os ratio, have been used extensively in dating terrestrial as well as meteoric
rock
s. 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 craton
s. However, the most notable application of Os in dating has been in conjunction with iridium
, to analyze the layer of shocked quartz
along the K-T boundary
that marks the extinction of the dinosaur
s 65 million years ago.
There are also 29 artificial radioisotopes, the longest-lived of which is 194Re with a half-life of 6 years, all others have half-lives under 94 days. There are also 9 known nuclear isomer
s, the longest-lived of which is 191mRe with a half-life of 13.10 hours.
Standard atomic mass: 190.23(3) u
Osmium
Osmium is a chemical element with the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-blacktransition metal in the platinum family, and is the densest natural element. Osmium is twice as dense as lead. The density of osmium is , slightly greater than that of iridium,...
(Os) has seven naturally occurring isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s, 6 of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other one, 186Os, has an extremely long half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
(2×1015 years) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
(half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/187Os ratio, have been used extensively in dating terrestrial as well as meteoric
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
s. 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 craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s. However, the most notable application of Os in dating has been in conjunction with iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
, to analyze the layer of shocked quartz
Shocked quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure , the crystalline structure of quartz will be deformed along planes inside the crystal...
along the K-T boundary
Cretaceous-Tertiary extinction event
The Cretaceous–Paleogene extinction event, formerly named and still commonly referred to as the Cretaceous-Tertiary extinction event, occurred approximately 65.5 million years ago at the end of the Maastrichtian age of the Cretaceous period. It was a large-scale mass extinction of animal and plant...
that marks the extinction of the dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s 65 million years ago.
There are also 29 artificial radioisotopes, the longest-lived of which is 194Re with a half-life of 6 years, all others have half-lives under 94 days. There are also 9 known nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
s, the longest-lived of which is 191mRe with a half-life of 13.10 hours.
Standard atomic mass: 190.23(3) u
Table
| nuclide symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-lifeBold for isotopes with half-lives longer than the age of the universe (nearly stable) | decay mode(s)Abbreviations: EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
daughter isotope(s)Bold for stable isotopes, bold italics for nearly stable isotopes (half-life longer than the age of the universe Age of the universe The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model... ) |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 162Os | 76 | 86 | 161.98443(54)# | 1.87(18) ms | α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less... |
158W | 0+ | ||
| 163Os | 76 | 87 | 162.98269(43)# | 5.5(6) ms | α | 159W | 7/2-# | ||
| β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... , p Proton decay In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron... (rare) |
162W | ||||||||
| β+ (rare) | 163Re | ||||||||
| 164Os | 76 | 88 | 163.97804(22) | 21(1) ms | α (98%) | 160W | 0+ | ||
| β+ (2%) | 164Re | ||||||||
| 165Os | 76 | 89 | 164.97676(22)# | 71(3) ms | α (60%) | 161W | (7/2-) | ||
| β+ (40%) | 165Re | ||||||||
| 166Os | 76 | 90 | 165.972691(20) | 216(9) ms | α (72%) | 162W | 0+ | ||
| β+ (28%) | 166Re | ||||||||
| 167Os | 76 | 91 | 166.97155(8) | 810(60) ms | α (67%) | 163W | 3/2-# | ||
| β+ (33%) | 167Re | ||||||||
| 168Os | 76 | 92 | 167.967804(13) | 2.06(6) s | β+ (51%) | 168Re | 0+ | ||
| α (49%) | 164W | ||||||||
| 169Os | 76 | 93 | 168.967019(27) | 3.40(9) s | β+ (89%) | 169Re | 3/2-# | ||
| α (11%) | 165W | ||||||||
| 170Os | 76 | 94 | 169.963577(12) | 7.46(23) s | β+ (91.4%) | 170Re | 0+ | ||
| α (8.6%) | 176W | ||||||||
| 171Os | 76 | 95 | 170.963185(20) | 8.3(2) s | β+ (98.3%) | 171Re | (5/2-) | ||
| α (1.7%) | 167W | ||||||||
| 172Os | 76 | 96 | 171.960023(16) | 19.2(5) s | β+ (98.9%) | 172Re | 0+ | ||
| α (1.1%) | 168W | ||||||||
| 173Os | 76 | 97 | 172.959808(16) | 22.4(9) s | β+ (99.6%) | 173Re | (5/2-) | ||
| α (.4%) | 169W | ||||||||
| 174Os | 76 | 98 | 173.957062(12) | 44(4) s | β+ (99.97%) | 174Re | 0+ | ||
| α (.024%) | 170W | ||||||||
| 175Os | 76 | 99 | 174.956946(15) | 1.4(1) min | β+ | 175Re | (5/2-) | ||
| 176Os | 76 | 100 | 175.95481(3) | 3.6(5) min | β+ | 176Re | 0+ | ||
| 177Os | 76 | 101 | 176.954965(17) | 3.0(2) min | β+ | 177Re | 1/2- | ||
| 178Os | 76 | 102 | 177.953251(18) | 5.0(4) min | β+ | 178Re | 0+ | ||
| 179Os | 76 | 103 | 178.953816(19) | 6.5(3) min | β+ | 179Re | (1/2-) | ||
| 180Os | 76 | 104 | 179.952379(22) | 21.5(4) min | β+ | 180Re | 0+ | ||
| 181Os | 76 | 105 | 180.95324(3) | 105(3) min | β+ | 181Re | 1/2- | ||
| 181m1Os | 48.9(2) keV | 2.7(1) min | β+ | 181Re | (7/2)- | ||||
| 181m2Os | 156.5(7) keV | 316(18) ns | (9/2)+ | ||||||
| 182Os | 76 | 106 | 181.952110(23) | 22.10(25) h | EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... |
182Re | 0+ | ||
| 183Os | 76 | 107 | 182.95313(5) | 13.0(5) h | β+ | 183Re | 9/2+ | ||
| 183mOs | 170.71(5) keV | 9.9(3) h | β+ (85%) | 183Re | 1/2- | ||||
| IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... (15%) |
183Os | ||||||||
| 184Os | 76 | 108 | 183.9524891(14) | Observationally StableBelieved to undergo α decay to 180W or β+β+ decay to 184W with a half-life over 56×1012 years | 0+ | 2(1)×10−4 | |||
| 185Os | 76 | 109 | 184.9540423(14) | 93.6(5) d | EC | 185Re | 1/2- | ||
| 185m1Os | 102.3(7) keV | 3.0(4) µs | (7/2-)# | ||||||
| 185m2Os | 275.7(8) keV | 0.78(5) µs | (11/2+) | ||||||
| 186Osprimordial Primordial nuclide In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known... radionuclide Radionuclide A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma... |
76 | 110 | 185.9538382(15) | 2.0(11)×1015 a | α | 182W | 0+ | 0.0159(3) | |
| 187OsUsed in rhenium-osmium dating Rhenium-osmium dating Rhenium-Osmium dating is a form of radiometric dating based on the beta decay of the isotope 187Re to 187Os. This normally occurs with a half-life of 41.6 × 109 y, but studies using fully ionised 187Re atoms have found that this can decrease to only 33 y... |
76 | 111 | 186.9557505(15) | Observationally StableBelieved to undergo α decay to 183W | 1/2- | 0.0196(2) | |||
| 188Os | 76 | 112 | 187.9558382(15) | Observationally StableBelieved to undergo α decay to 184W | 0+ | 0.1324(8) | |||
| 189Os | 76 | 113 | 188.9581475(16) | Observationally StableBelieved to undergo α decay to 185W | 3/2- | 0.1615(5) | |||
| 189mOs | 30.812(15) keV | 5.81(6) h | IT | 189Os | 9/2- | ||||
| 190Os | 76 | 114 | 189.9584470(16) | Observationally StableBelieved to undergo α decay to 186W | 0+ | 0.2626(2) | |||
| 190mOs | 1705.4(2) keV | 9.9(1) min | IT | 190Os | (10)- | ||||
| 191Os | 76 | 115 | 190.9609297(16) | 15.4(1) d | β- | 191Ir | 9/2- | ||
| 191mOs | 74.382(3) keV | 13.10(5) h | IT | 191Os | 3/2- | ||||
| 192Os | 76 | 116 | 191.9614807(27) | Observationally StableBelieved to undergo α decay to 188W or β-β- decay to 192Pt with a half-life over 9.8×1012 years | 0+ | 0.4078(19) | |||
| 192mOs | 2015.40(11) keV | 5.9(1) s | IT (87%) | 192Os | (10-) | ||||
| β- (13%) | 192Ir | ||||||||
| 193Os | 76 | 117 | 192.9641516(27) | 30.11(1) h | β- | 193Ir | 3/2- | ||
| 194Os | 76 | 118 | 193.9651821(28) | 6.0(2) a | β- | 194Ir | 0+ | ||
| 195Os | 76 | 119 | 194.96813(54) | 6.5 min | β- | 195Ir | 3/2-# | ||
| 196Os | 76 | 120 | 195.96964(4) | 34.9(2) min | β- | 196Ir | 0+ | ||
| 197Os | 76 | 121 | 2.8(6) min | ||||||