Isotopes of selenium
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Selenium 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 about 330,000 years, and 82Se, which has the very long half-life of 8.76×1019 years as it decays via double beta decay to krypton-82 and for practical purposes can be considered to be stable. There are 23 other unstable isotopes that have been characterized, the longest-lived after 79Se being 75Se with its half-life 119.78 days, 72Se at 8.40 days, and 73Se at 7.15 hours. The others are all under an hour and most do not exceed 38 seconds.
List of isotopes
| Nuclide | Z | N | Isotopic mass (Da) | Discovery year | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (mole fraction) | |
|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy | Normal proportion | Range of variation | ||||||||
| 63Se | 34 | 29 | 62.98191(54)# | 13.2(39) ms | β+, p (89%) | 62Ge | 3/2−# | |||
| β+ (11%) | 63As | |||||||||
| 2p? (<0.5%) | 61Ge | |||||||||
| 64Se | 34 | 30 | 63.97117(54)# | 22.6(2) ms | β+? | 64As | 0+ | |||
| β+, p? | 63Ge | |||||||||
| 65Se | 34 | 31 | 64.96455(32)# | 34.2(7) ms | β+, p (87%) | 64Ge | 3/2−# | |||
| β+ (13%) | 65As | |||||||||
| 66Se | 34 | 32 | 65.95528(22)# | 54(4) ms | β+ | 66As | 0+ | |||
| β+, p? | 65Ge | |||||||||
| 67Se | 34 | 33 | 66.949994(72) | 133(4) ms | β+ (99.5%) | 67As | 5/2−# | |||
| β+, p (0.5%) | 66Ge | |||||||||
| 68Se | 34 | 34 | 67.94182524(53) | 35.5(7) s | β+ | 68As | 0+ | |||
| 69Se | 34 | 35 | 68.9394148(16) | 27.4(2) s | β+ (99.95%) | 69As | 1/2− | |||
| β+, p (.052%) | 68Ge | |||||||||
| 69m1Se | 38.85(22) keV | 2.0(2) μs | IT | 69Se | 5/2− | |||||
| 69m2Se | 574.0(4) keV | 955(16) ns | IT | 69Se | 9/2+ | |||||
| 70Se | 34 | 36 | 69.9335155(17) | 41.1(3) min | β+ | 70As | 0+ | |||
| 71Se | 34 | 37 | 70.9322094(30) | 4.74(5) min | β+ | 71As | (5/2−) | |||
| 71m1Se | 48.79(5) keV | 5.6(7) μs | IT | 71Se | (1/2−) | |||||
| 71m2Se | 260.48(10) keV | 19.0(5) μs | IT | 71Se | (9/2+) | |||||
| 72Se | 34 | 38 | 71.9271405(21) | 8.40(8) d | EC | 72As | 0+ | |||
| 73Se | 34 | 39 | 72.9267549(80) | 7.15(9) h | β+ | 73As | 9/2+ | |||
| 73mSe | 25.71(4) keV | 39.8(17) min | IT (72.6%) | 73Se | 3/2− | |||||
| β+ (27.4%) | 73As | |||||||||
| 74Se | 34 | 40 | 73.922475933(15) | Observationally Stable | 0+ | 0.0086(3) | ||||
| 75Se | 34 | 41 | 74.922522870(78) | 119.78(3) d | EC | 75As | 5/2+ | |||
| 76Se | 34 | 42 | 75.919213702(17) | Stable | 0+ | 0.0923(7) | ||||
| 77Se | 34 | 43 | 76.919914150(67) | Stable | 1/2− | 0.0760(7) | ||||
| 77mSe | 161.9223(10) keV | 17.36(5) s | IT | 77Se | 7/2+ | |||||
| 78Se | 34 | 44 | 77.91730924(19) | Stable | 0+ | 0.2369 (22) | ||||
| 79Se | 34 | 45 | 78.91849925(24) | 3.27(28)×105 y | β− | 79Br | 7/2+ | |||
| 79mSe | 95.77(3) keV | 3.900(18) min | IT (99.94%) | 79Se | 1/2− | |||||
| β− (0.056%) | 79Br | |||||||||
| 80Se | 34 | 46 | 79.9165218(10) | Observationally Stable | 0+ | 0.4980(36) | ||||
| 81Se | 34 | 47 | 80.9179930(10) | 18.45(12) min | β− | 81Br | 1/2− | |||
| 81mSe | 103.00(6) keV | 57.28(2) min | IT (99.95%) | 81Se | 7/2+ | |||||
| β− (0.051%) | 81Br | |||||||||
| 82Se | 34 | 48 | 81.91669953(50) | 8.76(15)×1019 y | β−β− | 82Kr | 0+ | 0.0882(15) | ||
| 83Se | 34 | 49 | 82.9191186(33) | 22.25(4) min | β− | 83Br | 9/2+ | |||
| 83mSe | 228.92(7) keV | 70.1(4) s | β− | 83Br | 1/2− | |||||
| 84Se | 34 | 50 | 83.9184668(21) | 3.26(10) min | β− | 84Br | 0+ | |||
| 85Se | 34 | 51 | 84.9222608(28) | 32.9(3) s | β− | 85Br | (5/2)+ | |||
| 86Se | 34 | 52 | 85.9243117(27) | 14.3(3) s | β− | 86Br | 0+ | |||
| β−, n? | 85Br | |||||||||
| 87Se | 34 | 53 | 86.9286886(24) | 5.50(6) s | β− (99.50%) | 87Br | (3/2+) | |||
| β−, n (0.60%) | 86Br | |||||||||
| 88Se | 34 | 54 | 87.9314175(36) | 1.53(6) s | β− (99.01%) | 88Br | 0+ | |||
| β−, n (0.99%) | 87Br | |||||||||
| 89Se | 34 | 55 | 88.9366691(40) | 430(50) ms | β− (92.2%) | 89Br | 5/2+# | |||
| β−, n (7.8%) | 88Br | |||||||||
| 90Se | 34 | 56 | 89.94010(35) | 210(80) ms | β− | 90Br | 0+ | |||
| β−, n? | 89Br | |||||||||
| 91Se | 34 | 57 | 90.94570(47) | 270(50) ms | β− (79%) | 91Br | 1/2+# | |||
| β−, n (21%) | 90Br | |||||||||
| β−, 2n? | 89Br | |||||||||
| 92Se | 34 | 58 | 91.94984(43)# | 90# ms [>300 ns] | β−? | 92Br | 0+ | |||
| β−, n? | 91Br | |||||||||
| β−, 2n? | 90Br | |||||||||
| 92mSe | 3072(2) keV | 15.7(7) μs | IT | 92Se | (9−) | |||||
| 93Se | 34 | 59 | 92.95614(43)# | 130# ms [>300 ns] | β−? | 93Br | 1/2+# | |||
| β−, n? | 92Br | |||||||||
| β−, 2n? | 91Br | |||||||||
| 93mSe | 678.2(7) keV | 420(100) ns | IT | 93Se | ||||||
| 94Se | 34 | 60 | 93.96049(54)# | 50# ms [>300 ns] | β−? | 94Br | 0+ | |||
| β−, n? | 93Br | |||||||||
| β−, 2n? | 92Br | |||||||||
| 94mSe | 2430.0(6) keV | 680(50) ns | IT | 94Se | (7−) | |||||
| 95Se | 34 | 61 | 94.96730(54)# | 70# ms [>400 ns] | β−? | 95Br | 3/2+# | |||
| β−, n? | 94Br | |||||||||
| β−, 2n? | 93Br | |||||||||
| 96Se | 34 | 62 | ||||||||
| 97Se | 34 | 63 | ||||||||
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Use of radioisotopes
The isotope selenium-75 has radiopharmaceutical uses. For example, it is used in high-dose-rate endorectal brachytherapy, as an alternative to iridium-192.
In paleobiogeochemistry, the ratio in amount of selenium-82 to selenium-76 (i.e, the value of δ82/76Se) can be used to track down the redox conditions on Earth during the Neoproterozoic era in order to gain a deeper understanding of the rapid oxygenation that trigger the emergence of complex organisms.
See also
Daughter products other than selenium
- Isotope masses from: Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), , Nuclear Physics A, 729: 3–128, Bibcode:, doi:
- Isotopic compositions and standard atomic masses from: de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). . Pure and Applied Chemistry. 75 (6): 683–800. doi:. Wieser, Michael E. (2006). . Pure and Applied Chemistry. 78 (11): 2051–2066. doi:.
- . International Union of Pure and Applied Chemistry. 19 October 2005.
- Half-life, spin, and isomer data selected from the following sources. Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), , Nuclear Physics A, 729: 3–128, Bibcode:, doi: National Nuclear Data Center. . Brookhaven National Laboratory. Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.