Isotopes of selenium

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 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

|-id=Selenium-63 | rowspan=3|⁶³Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 29 | rowspan=3|62.98191(54)# | rowspan=3|13.2(39)&nbsp;ms | β⁺, p (89%) | ⁶²Ge | rowspan=3|3/2−# | rowspan=3| | rowspan=3| |- | β⁺ (11%) | ⁶³As |- | 2p? (<0.5%) | ⁶¹Ge |-id=Selenium-64 | rowspan=2|⁶⁴Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 30 | rowspan=2|63.97117(54)# | rowspan=2|22.6(2)&nbsp;ms | β⁺? | ⁶⁴As | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁶³Ge |-id=Selenium-65 | rowspan=2|⁶⁵Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 31 | rowspan=2|64.96455(32)# | rowspan=2|34.2(7)&nbsp;ms | β⁺, p (87%) | ⁶⁴Ge | rowspan=2|3/2−# | rowspan=2| | rowspan=2| |- | β⁺ (13%) | ⁶⁵As |-id=Selenium-66 | rowspan=2|⁶⁶Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 32 | rowspan=2|65.95528(22)# | rowspan=2|54(4)&nbsp;ms | β⁺ | ⁶⁶As | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁶⁵Ge |-id=Selenium-67 | rowspan=2|⁶⁷Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 33 | rowspan=2|66.949994(72) | rowspan=2|133(4)&nbsp;ms | β⁺ (99.5%) | ⁶⁷As | rowspan=2|5/2−# | rowspan=2| | rowspan=2| |- | β⁺, p (0.5%) | ⁶⁶Ge |-id=Selenium-68 | ⁶⁸Se | style="text-align:right" | 34 | style="text-align:right" | 34 | 67.94182524(53) | 35.5(7)&nbsp;s | β⁺ | ⁶⁸As | 0+ | | |-id=Selenium-69 | rowspan=2|⁶⁹Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 35 | rowspan=2|68.9394148(16) | rowspan=2|27.4(2)&nbsp;s | β⁺ (99.95%) | ⁶⁹As | rowspan=2|1/2− | rowspan=2| | rowspan=2| |- | β⁺, p (.052%) | ⁶⁸Ge |-id=Selenium-69m1 | style="text-indent:1em" | ^69m1Se | colspan="3" style="text-indent:2em" | 38.85(22)&nbsp;keV | 2.0(2)&nbsp;μs | IT | ⁶⁹Se | 5/2− | | |-id=Selenium-69m2 | style="text-indent:1em" | ^69m2Se | colspan="3" style="text-indent:2em" | 574.0(4)&nbsp;keV | 955(16)&nbsp;ns | IT | ⁶⁹Se | 9/2+ | | |-id=Selenium-70 | ⁷⁰Se | style="text-align:right" | 34 | style="text-align:right" | 36 | 69.9335155(17) | 41.1(3)&nbsp;min | β⁺ | ⁷⁰As | 0+ | | |-id=Selenium-71 | ⁷¹Se | style="text-align:right" | 34 | style="text-align:right" | 37 | 70.9322094(30) | 4.74(5)&nbsp;min | β⁺ | ⁷¹As | (5/2−) | | |-id=Selenium-71m1 | style="text-indent:1em" | ^71m1Se | colspan="3" style="text-indent:2em" | 48.79(5)&nbsp;keV | 5.6(7)&nbsp;μs | IT | ⁷¹Se | (1/2−) | | |-id=Selenium-71m2 | style="text-indent:1em" | ^71m2Se | colspan="3" style="text-indent:2em" | 260.48(10)&nbsp;keV | 19.0(5)&nbsp;μs | IT | ⁷¹Se | (9/2+) | | |-id=Selenium-72 | ⁷²Se | style="text-align:right" | 34 | style="text-align:right" | 38 | 71.9271405(21) | 8.40(8)&nbsp;d | EC | ⁷²As | 0+ | | |-id=Selenium-73 | ⁷³Se | style="text-align:right" | 34 | style="text-align:right" | 39 | 72.9267549(80) | 7.15(9)&nbsp;h | β⁺ | ⁷³As | 9/2+ | | |-id=Selenium-73m | rowspan=2 style="text-indent:1em" | ^73mSe | rowspan=2 colspan="3" style="text-indent:2em" | 25.71(4)&nbsp;keV | rowspan=2|39.8(17)&nbsp;min | IT (72.6%) | ⁷³Se | rowspan=2|3/2− | rowspan=2| | rowspan=2| |- | β⁺ (27.4%) | ⁷³As |-id=Selenium-74 | ⁷⁴Se | style="text-align:right" | 34 | style="text-align:right" | 40 | 73.922475933(15) | colspan=3 align=center|Observationally Stable | 0+ | 0.0086(3) | |-id=Selenium-75 | ⁷⁵Se | style="text-align:right" | 34 | style="text-align:right" | 41 | 74.922522870(78) | 119.78(3)&nbsp;d | EC | ⁷⁵As | 5/2+ | | |-id=Selenium-76 | ⁷⁶Se | style="text-align:right" | 34 | style="text-align:right" | 42 | 75.919213702(17) | colspan=3 align=center|Stable | 0+ | 0.0923(7) | |-id=Selenium-77 | ⁷⁷Se | style="text-align:right" | 34 | style="text-align:right" | 43 | 76.919914150(67) | colspan=3 align=center|Stable | 1/2− | 0.0760(7) | |-id=Selenium-77m | style="text-indent:1em" | ^77mSe | colspan="3" style="text-indent:2em" | 161.9223(10)&nbsp;keV | 17.36(5)&nbsp;s | IT | ⁷⁷Se | 7/2+ | | |-id=Selenium-78 | ⁷⁸Se | style="text-align:right" | 34 | style="text-align:right" | 44 | 77.91730924(19) | colspan=3 align=center|Stable | 0+ | 0.2369 (22) | |-id=Selenium-79 | ⁷⁹Se | style="text-align:right" | 34 | style="text-align:right" | 45 | 78.91849925(24) | 3.27(28)×10⁵&nbsp;y | β^− | ⁷⁹Br | 7/2+ | | |-id=Selenium-79m | rowspan=2 style="text-indent:1em" | ^79mSe | rowspan=2 colspan="3" style="text-indent:2em" | 95.77(3)&nbsp;keV | rowspan=2|3.900(18)&nbsp;min | IT (99.94%) | ⁷⁹Se | rowspan=2|1/2− | rowspan=2| | rowspan=2| |- | β^− (0.056%) | ⁷⁹Br |-id=Selenium-80 | ⁸⁰Se | style="text-align:right" | 34 | style="text-align:right" | 46 | 79.9165218(10) | colspan=3 align=center|Observationally Stable | 0+ | 0.4980(36) | |-id=Selenium-81 | ⁸¹Se | style="text-align:right" | 34 | style="text-align:right" | 47 | 80.9179930(10) | 18.45(12)&nbsp;min | β^− | ⁸¹Br | 1/2− | | |-id=Selenium-81m | rowspan=2 style="text-indent:1em" | ^81mSe | rowspan=2 colspan="3" style="text-indent:2em" | 103.00(6)&nbsp;keV | rowspan=2|57.28(2)&nbsp;min | IT (99.95%) | ⁸¹Se | rowspan=2|7/2+ | rowspan=2| | rowspan=2| |- | β^− (0.051%) | ⁸¹Br |-id=Selenium-82 | ⁸²Se | style="text-align:right" | 34 | style="text-align:right" | 48 | 81.91669953(50) | 8.76(15)×10¹⁹ y | β^−β^− | ⁸²Kr | 0+ | 0.0882(15) | |-id=Selenium-83 | ⁸³Se | style="text-align:right" | 34 | style="text-align:right" | 49 | 82.9191186(33) | 22.25(4)&nbsp;min | β^− | ⁸³Br | 9/2+ | | |-id=Selenium-83m | style="text-indent:1em" | ^83mSe | colspan="3" style="text-indent:2em" | 228.92(7)&nbsp;keV | 70.1(4)&nbsp;s | β^− | ⁸³Br | 1/2− | | |-id=Selenium-84 | ⁸⁴Se | style="text-align:right" | 34 | style="text-align:right" | 50 | 83.9184668(21) | 3.26(10)&nbsp;min | β^− | ⁸⁴Br | 0+ | | |-id=Selenium-85 | ⁸⁵Se | style="text-align:right" | 34 | style="text-align:right" | 51 | 84.9222608(28) | 32.9(3)&nbsp;s | β^− | ⁸⁵Br | (5/2)+ | | |-id=Selenium-86 | rowspan=2|⁸⁶Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 52 | rowspan=2|85.9243117(27) | rowspan=2|14.3(3)&nbsp;s | β^− | ⁸⁶Br | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n? | ⁸⁵Br |-id=Selenium-87 | rowspan=2|⁸⁷Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 53 | rowspan=2|86.9286886(24) | rowspan=2|5.50(6)&nbsp;s | β^− (99.50%) | ⁸⁷Br | rowspan=2|(3/2+) | rowspan=2| | rowspan=2| |- | β^−, n (0.60%) | ⁸⁶Br |-id=Selenium-88 | rowspan=2|⁸⁸Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 54 | rowspan=2|87.9314175(36) | rowspan=2|1.53(6)&nbsp;s | β^− (99.01%) | ⁸⁸Br | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n (0.99%) | ⁸⁷Br |-id=Selenium-89 | rowspan=2|⁸⁹Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 55 | rowspan=2|88.9366691(40) | rowspan=2|430(50)&nbsp;ms | β^− (92.2%) | ⁸⁹Br | rowspan=2|5/2+# | rowspan=2| | rowspan=2| |- | β^−, n (7.8%) | ⁸⁸Br |-id=Selenium-90 | rowspan=2|⁹⁰Se | rowspan=2 style="text-align:right" | 34 | rowspan=2 style="text-align:right" | 56 | rowspan=2|89.94010(35) | rowspan=2|210(80)&nbsp;ms | β^− | ⁹⁰Br | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n? | ⁸⁹Br |-id=Selenium-91 | rowspan=3|⁹¹Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 57 | rowspan=3|90.94570(47) | rowspan=3|270(50)&nbsp;ms | β^− (79%) | ⁹¹Br | rowspan=3|1/2+# | rowspan=3| | rowspan=3| |- | β^−, n (21%) | ⁹⁰Br |- | β^−, 2n? | ⁸⁹Br |-id=Selenium-92 | rowspan=3|⁹²Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 58 | rowspan=3|91.94984(43)# | rowspan=3|90#&nbsp;ms [>300&nbsp;ns] | β^−? | ⁹²Br | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n? | ⁹¹Br |- | β^−, 2n? | ⁹⁰Br |-id=Selenium-92m | style="text-indent:1em" | ^92mSe | colspan="3" style="text-indent:2em" | 3072(2)&nbsp;keV | 15.7(7)&nbsp;μs | IT | ⁹²Se | (9−) | | |-id=Selenium-93 | rowspan=3|⁹³Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 59 | rowspan=3|92.95614(43)# | rowspan=3|130#&nbsp;ms [>300&nbsp;ns] | β^−? | ⁹³Br | rowspan=3|1/2+# | rowspan=3| | rowspan=3| |- | β^−, n? | ⁹²Br |- | β^−, 2n? | ⁹¹Br |-id=Selenium-93m | style="text-indent:1em" | ^93mSe | colspan="3" style="text-indent:2em" | 678.2(7)&nbsp;keV | 420(100)&nbsp;ns | IT | ⁹³Se | | | |-id=Selenium-94 | rowspan=3|⁹⁴Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 60 | rowspan=3|93.96049(54)# | rowspan=3|50#&nbsp;ms [>300&nbsp;ns] | β^−? | ⁹⁴Br | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n? | ⁹³Br |- | β^−, 2n? | ⁹²Br |-id=Selenium-94m | style="text-indent:1em" | ^94mSe | colspan="3" style="text-indent:2em" | 2430.0(6)&nbsp;keV | 680(50)&nbsp;ns | IT | ⁹⁴Se | (7−) | | |-id=Selenium-95 | rowspan=3|⁹⁵Se | rowspan=3 style="text-align:right" | 34 | rowspan=3 style="text-align:right" | 61 | rowspan=3|94.96730(54)# | rowspan=3|70#&nbsp;ms [>400&nbsp;ns] | β^−? | ⁹⁵Br | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β^−, n? | ⁹⁴Br |- | β^−, 2n? | ⁹³Br |-id=Selenium-96 | ⁹⁶Se | style="text-align:right" | 34 | style="text-align:right" | 62 | | | | | | | |-id=Selenium-97 | ⁹⁷Se | style="text-align:right" | 34 | style="text-align:right" | 63 | | | | | | |

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 δ^82/76Se) 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

• Isotopes of krypton
• Isotopes of bromine
• Isotopes of arsenic
• Isotopes of germanium

References

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources.