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Standard atomic weight Ar°(Kr) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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There are 34 known isotopes of krypton (36Kr) with atomic mass numbers from 69 through 102. [5] [6] Naturally occurring krypton is made of five stable isotopes and one (78
Kr
) which is slightly radioactive with an extremely long half-life, plus traces of radioisotopes that are produced by cosmic rays in the atmosphere.
Nuclide [n 1] | Z | N | Isotopic mass (Da) [7] [n 2] [n 3] | Half-life [1] [n 4] [n 5] | Decay mode [1] [n 6] | Daughter isotope [n 7] [n 8] | Spin and parity [1] [n 9] [n 5] | Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion [1] | Range of variation | |||||||||||||||||
67Kr | 36 | 31 | 66.98331(46)# | 7.4(29) ms | β+? (63%) | 67Br | 3/2-# | ||||||||||||
2p (37%) | 65Se | ||||||||||||||||||
68Kr | 36 | 32 | 67.97249(54)# | 21.6(33) ms | β+, p (>90%) | 67Se | 0+ | ||||||||||||
β+? (<10%) | 68Br | ||||||||||||||||||
p? | 67Br | ||||||||||||||||||
69Kr | 36 | 33 | 68.96550(32)# | 27.9(8) ms | β+, p (94%) | 68Se | (5/2−) | ||||||||||||
β+ (6%) | 69Br | ||||||||||||||||||
70Kr | 36 | 34 | 69.95588(22)# | 45.00(14) ms | β+ (>98.7%) | 70Br | 0+ | ||||||||||||
β+, p (<1.3%) | 69Se | ||||||||||||||||||
71Kr | 36 | 35 | 70.95027(14) | 98.8(3) ms | β+ (97.9%) | 71Br | (5/2)− | ||||||||||||
β+, p (2.1%) | 70Se | ||||||||||||||||||
72Kr | 36 | 36 | 71.9420924(86) | 17.16(18) s | β+ | 72Br | 0+ | ||||||||||||
73Kr | 36 | 37 | 72.9392892(71) | 27.3(10) s | β+ (99.75%) | 73Br | (3/2)− | ||||||||||||
β+, p (0.25%) | 72Se | ||||||||||||||||||
73mKr | 433.55(13) keV | 107(10) ns | IT | 73Kr | (9/2+) | ||||||||||||||
74Kr | 36 | 38 | 73.9330840(22) | 11.50(11) min | β+ | 74Br | 0+ | ||||||||||||
75Kr | 36 | 39 | 74.9309457(87) | 4.60(7) min | β+ | 75Br | 5/2+ | ||||||||||||
76Kr | 36 | 40 | 75.9259107(43) | 14.8(1) h | β+ | 76Br | 0+ | ||||||||||||
77Kr | 36 | 41 | 76.9246700(21) | 72.6(9) min | β+ | 77Br | 5/2+ | ||||||||||||
77mKr | 66.50(5) keV | 118(12) ns | IT | 77Kr | 3/2− | ||||||||||||||
78Kr [n 10] | 36 | 42 | 77.92036634(33) | 9.2 +5.5 −2.6±1.3×1021 y [2] | Double EC | 78Se | 0+ | 0.00355(3) | |||||||||||
79Kr | 36 | 43 | 78.9200829(37) | 35.04(10) h | β+ | 79Br | 1/2− | ||||||||||||
79mKr | 129.77(5) keV | 50(3) s | IT | 79Kr | 7/2+ | ||||||||||||||
80Kr | 36 | 44 | 79.91637794(75) | Stable | 0+ | 0.02286(10) | |||||||||||||
81Kr [n 11] | 36 | 45 | 80.9165897(12) | 2.29(11)×105 y | EC | 81Br | 7/2+ | 6×10−13 [8] | |||||||||||
81mKr | 190.64(4) keV | 13.10(3) s | IT | 81Kr | 1/2− | ||||||||||||||
EC (0.0025%) | 81Br | ||||||||||||||||||
82Kr | 36 | 46 | 81.9134811537(59) | Stable | 0+ | 0.11593(31) | |||||||||||||
83Kr [n 12] | 36 | 47 | 82 914126.516(9) | Stable | 9/2+ | 0.11500(19) | |||||||||||||
83m1Kr | 9.4053(8) keV | 156.8(5) ns | IT | 83Kr | 7/2+ | ||||||||||||||
83m2Kr | 41.5575(7) keV | 1.830(13) h | IT | 83Kr | 1/2− | ||||||||||||||
84Kr [n 12] | 36 | 48 | 83.9114977271(41) | Stable | 0+ | 0.56987(15) | |||||||||||||
84mKr | 3236.07(18) keV | 1.83(4) μs | IT | 84Kr | 8+ | ||||||||||||||
85Kr [n 12] | 36 | 49 | 84.9125273(21) | 10.728(7) y | β− | 85Rb | 9/2+ | 1×10−11 [8] | |||||||||||
85m1Kr | 304.871(20) keV | 4.480(8) h | β− (78.8%) | 85Rb | 1/2− | ||||||||||||||
IT (21.2%) | 85Kr | ||||||||||||||||||
85m2Kr | 1991.8(2) keV | 1.82(5) μs | IT | 85Kr | (17/2+) | ||||||||||||||
86Kr [n 13] [n 12] | 36 | 50 | 85.9106106247(40) | Observationally Stable [n 14] | 0+ | 0.17279(41) | |||||||||||||
87Kr | 36 | 51 | 86.91335476(26) | 76.3(5) min | β− | 87Rb | 5/2+ | ||||||||||||
88Kr | 36 | 52 | 87.9144479(28) | 2.825(19) h | β− | 88Rb | 0+ | ||||||||||||
89Kr [n 12] | 36 | 53 | 88.9178354(23) | 3.15(4) min | β− | 89Rb | 3/2+ | ||||||||||||
90Kr | 36 | 54 | 89.9195279(20) | 32.32(9) s | β− | 90mRb | 0+ | ||||||||||||
91Kr | 36 | 55 | 90.9238063(24) | 8.57(4) s | β− | 91Rb | 5/2+ | ||||||||||||
β−, n? | 90Rb | ||||||||||||||||||
92Kr [n 12] | 36 | 56 | 91.9261731(29) | 1.840(8) s | β− (99.97%) | 92Rb | 0+ | ||||||||||||
β−, n (0.0332%) | 91Rb | ||||||||||||||||||
93Kr | 36 | 57 | 92.9311472(27) | 1.287(10) s | β− (98.05%) | 93Rb | 1/2+ | ||||||||||||
β−, n (1.95%) | 92Rb | ||||||||||||||||||
94Kr | 36 | 58 | 93.934140(13) | 212(4) ms | β− (98.89%) | 94Rb | 0+ | ||||||||||||
β−, n (1.11%) | 93Rb | ||||||||||||||||||
95Kr | 36 | 59 | 94.939711(20) | 114(3) ms | β− (97.13%) | 95Rb | 1/2+ | ||||||||||||
β−, n (2.87%) | 94Rb | ||||||||||||||||||
β−, 2n? | 93Rb | ||||||||||||||||||
95mKr | 195.5(3) keV | 1.582(22) μs | IT | 85Kr | (7/2+) | ||||||||||||||
96Kr | 36 | 60 | 95.942998(62) [9] | 80(8) ms | β− (96.3%) | 96Rb | 0+ | ||||||||||||
β−, n (3.7%) | 95Rb | ||||||||||||||||||
97Kr | 36 | 61 | 96.94909(14) | 62.2(32) ms | β− (93.3%) | 97Rb | 3/2+# | ||||||||||||
β−, n (6.7%) | 96Rb | ||||||||||||||||||
β−, 2n? | 95Rb | ||||||||||||||||||
98Kr | 36 | 62 | 97.95264(32)# | 42.8(36) ms | β− (93.0%) | 98Rb | 0+ | ||||||||||||
β−, n (7.0%) | 97Rb | ||||||||||||||||||
β−, 2n? | 96Rb | ||||||||||||||||||
99Kr | 36 | 63 | 98.95878(43)# | 40(11) ms | β− (89%) | 99Rb | 5/2−# | ||||||||||||
β−, n (11%) | 98Rb | ||||||||||||||||||
β−, 2n? | 97Rb | ||||||||||||||||||
100Kr | 36 | 64 | 99.96300(43)# | 12(8) ms | β− | 100Rb | 0+ | ||||||||||||
β−, n? | 99Rb | ||||||||||||||||||
β−, 2n? | 98Rb | ||||||||||||||||||
101Kr | 36 | 65 | 100.96932(54)# | 9# ms [>400 ns] | β−? | 101Rb | 5/2+# | ||||||||||||
β−, n? | 100Rb | ||||||||||||||||||
β−, 2n? | 99Rb | ||||||||||||||||||
102Kr [10] | 36 | 66 | 0+ | ||||||||||||||||
103Kr [11] | 36 | 67 | |||||||||||||||||
This table header & footer: |
n: | Neutron emission |
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Radioactive krypton-81 is the product of spallation reactions with cosmic rays striking gases present in the Earth atmosphere, along with the six stable or nearly stable krypton isotopes. [12] Krypton-81 has a half-life of about 229,000 years.
Krypton-81 is used for dating ancient (50,000- to 800,000-year-old) groundwater and to determine their residence time in deep aquifers. One of the main technical limitations of the method is that it requires the sampling of very large volumes of water: several hundred liters or a few cubic meters of water. This is particularly challenging for dating pore water in deep clay aquitards with very low hydraulic conductivity. [13]
Krypton-85 has a half-life of about 10.75 years. This isotope is produced by the nuclear fission of uranium and plutonium in nuclear weapons testing and in nuclear reactors, as well as by cosmic rays. An important goal of the Limited Nuclear Test Ban Treaty of 1963 was to eliminate the release of such radioisotopes into the atmosphere, and since 1963 much of that krypton-85 has had time to decay. However, it is inevitable that krypton-85 is released during the reprocessing of fuel rods from nuclear reactors.[ citation needed ]
The atmospheric concentration of krypton-85 around the North Pole is about 30 percent higher than that at the Amundsen–Scott South Pole Station because nearly all of the world's nuclear reactors and all of its major nuclear reprocessing plants are located in the northern hemisphere, and also well-north of the equator. [14] To be more specific, those nuclear reprocessing plants with significant capacities are located in the United States, the United Kingdom, the French Republic, the Russian Federation, Mainland China (PRC), Japan, India, and Pakistan.
Krypton-86 was formerly used to define the meter from 1960 until 1983, when the definition of the meter was based on the wavelength of the 606 nm (orange) spectral line of a krypton-86 atom. [15]
All other radioisotopes of krypton have half-lives of less than one day, except for krypton-79, a positron emitter with a half-life of about 35.0 hours.
Thallium (81Tl) has 41 isotopes with atomic masses that range from 176 to 216. 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 Tl radioisotopes. All isotopes of thallium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
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 40 radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spin quantum numbers of 1/2 and 3/2 respectively. All isotopes of mercury are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. These isotopes are predicted to undergo either alpha decay or double beta decay.
Natural hafnium (72Hf) consists of five observationally stable isotopes (176Hf, 177Hf, 178Hf, 179Hf, and 180Hf) and one very long-lived radioisotope, 174Hf, with a half-life of 7.0×1016 years. In addition, there are 34 known synthetic radioisotopes, the most stable of which is 182Hf with a half-life of 8.9×106 years. This extinct radionuclide is used in hafnium–tungsten dating to study the chronology of planetary differentiation.
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 a lower limit on its half-life of more than 1.3×1021 years has been set experimentally.
Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm and 148Sm, with 152Sm being the most abundant. 146Sm is also fairly long-lived, but is not long-lived enough to have survived in significant quantities from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System as an extinct radionuclide. It is the longest-lived nuclide that has not yet been confirmed to be primordial.
Naturally occurring barium (56Ba) is a mix of six stable isotopes and one very long-lived radioactive primordial isotope, barium-130, identified as being unstable by geochemical means (from analysis of the presence of its daughter xenon-130 in rocks) in 2001. This nuclide decays by double electron capture (absorbing two electrons and emitting two neutrinos), with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe).
There are 39 known isotopes and 17 nuclear isomers of tellurium (52Te), with atomic masses that range from 104 to 142. These are listed in the table below.
Tin (50Sn) is the element with the greatest number of stable isotopes. This is probably related to the fact that 50 is a "magic number" of protons. In addition, twenty-nine unstable tin isotopes are known, including tin-100 (100Sn) and tin-132 (132Sn), which are both "doubly magic". The longest-lived tin radioisotope is tin-126 (126Sn), with a half-life of 230,000 years. The other 28 radioisotopes have half-lives of less than a year.
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 4.41×1014 years, much longer than the currently accepted age of the Universe.
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-lives that are less than an hour except 100Rh and 105Rh. 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.
Technetium (43Tc) is one of the two elements with Z < 83 that have no stable isotopes; the other such element is promethium. It is primarily artificial, with 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 97Tc, 98Tc, and 99Tc.
Naturally occurring niobium (41Nb) is composed of one stable isotope (93Nb). The most stable radioisotope is 92Nb with a half-life of 34.7 million years. The next longest-lived niobium isotopes are 94Nb and 91Nb with a half-life of 680 years. There is also a meta state of 93Nb at 31 keV whose half-life is 16.13 years. Twenty-seven other radioisotopes have been characterized. Most of these have half-lives that are less than two hours, except 95Nb, 96Nb and 90Nb. The primary decay mode before stable 93Nb is electron capture and the primary mode after is beta emission with some neutron emission occurring in 104–110Nb.
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. Thirty other radioisotopes have been observed. All have half-lives less than a day except for 95Zr (64.02 days), 88Zr (83.4 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.
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. Thirty-five unstable isotopes have been characterized.
Rubidium (37Rb) has 36 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%).
Selenium (34Se) has six natural isotopes that occur in significant quantities, along with the trace isotope 79Se, which occurs in minute quantities in uranium ores. Five of these isotopes 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.
Bromine (35Br) has two stable isotopes, 79Br and 81Br, and 35 known radioisotopes, the most stable of which is 77Br, with a half-life of 57.036 hours.
Arsenic (33As) has 32 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 with a half-life of 80 days.
Copper (29Cu) has two stable isotopes, 63Cu and 65Cu, along with 28 radioisotopes. The most stable radioisotope is 67Cu with a half-life of 61.83 hours. Most of the others 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−.
Naturally occurring vanadium (23V) is composed of one stable isotope 51V and one radioactive isotope 50V with a half-life of 2.71×1017 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.