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 A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate stalls for individual animals and livestock. There are many different types of stables in use today; the ...

: ⁷⁴Se, ⁷⁶Se, ⁷⁷Se, ⁷⁸Se, and ⁸⁰Se. The last three also occur as

fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

, along with ⁷⁹Se, which has a half-life of 327,000 years,The half-life of ⁷⁹Se
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.

List of isotopes

, - , rowspan=2, ⁶⁵Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 31 , rowspan=2, 64.96466(64)# , rowspan=2, <50 ms , β⁺ (>99.9%) , ⁶⁵As , rowspan=2, 3/2−# , rowspan=2, , rowspan=2, , - , β⁺, p (<.1%) , ⁶⁴Ge , - , ⁶⁶Se , style="text-align:right" , 34 , style="text-align:right" , 32 , 65.95521(32)# , 33(12) ms , β⁺ , ⁶⁶As , 0+ , , , - , rowspan=2, ⁶⁷Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 33 , rowspan=2, 66.95009(21)# , rowspan=2, 133(11) ms , β⁺ (99.5%) , ⁶⁷As , rowspan=2, 5/2−# , rowspan=2, , rowspan=2, , - , β⁺, p (.5%) , ⁶⁶Ge , - , ⁶⁸Se , style="text-align:right" , 34 , style="text-align:right" , 34 , 67.94180(4) , 35.5(7) s , β⁺ , ⁶⁸As , 0+ , , , - , rowspan=2, ⁶⁹Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 35 , rowspan=2, 68.93956(4) , rowspan=2, 27.4(2) s , β⁺ (99.955%) , ⁶⁹As , rowspan=2, (1/2−) , rowspan=2, , rowspan=2, , - , β⁺, p (.045%) , ⁶⁸Ge , - , style="text-indent:1em" , ^69m1Se , colspan="3" style="text-indent:2em" , 39.4(1) keV , 2.0(2) μs , , , 5/2− , , , - , style="text-indent:1em" , ^69m2Se , colspan="3" style="text-indent:2em" , 573.9(10) keV , 955(16) ns , , , 9/2+ , , , - , ⁷⁰Se , style="text-align:right" , 34 , style="text-align:right" , 36 , 69.93339(7) , 41.1(3) min , β⁺ , ⁷⁰As , 0+ , , , - , ⁷¹Se , style="text-align:right" , 34 , style="text-align:right" , 37 , 70.93224(3) , 4.74(5) min , β⁺ , ⁷¹As , 5/2− , , , - , style="text-indent:1em" , ^71m1Se , colspan="3" style="text-indent:2em" , 48.79(5) keV , 5.6(7) μs , , , 1/2− to 9/2− , , , - , style="text-indent:1em" , ^71m2Se , colspan="3" style="text-indent:2em" , 260.48(10) keV , 19.0(5) μs , , , (9/2)+ , , , - , ⁷²Se , style="text-align:right" , 34 , style="text-align:right" , 38 , 71.927112(13) , 8.40(8) d , EC , ⁷²As , 0+ , , , - , ⁷³Se , style="text-align:right" , 34 , style="text-align:right" , 39 , 72.926765(11) , 7.15(8) h , β⁺ , ⁷³As , 9/2+ , , , - , rowspan=2 style="text-indent:1em" , ^73mSe , rowspan=2 colspan="3" style="text-indent:2em" , 25.71(4) keV , rowspan=2, 39.8(13) min , IT , ⁷³Se , rowspan=2, 3/2− , rowspan=2, , rowspan=2, , - , β⁺ , ⁷³As , - , ⁷⁴Se , style="text-align:right" , 34 , style="text-align:right" , 40 , 73.9224764(18) , colspan=3 align=center, Observationally StableBelieved to decay by β⁺β⁺ to ⁷⁴Ge , 0+ , 0.0089(4) , , - , ⁷⁵Se , style="text-align:right" , 34 , style="text-align:right" , 41 , 74.9225234(18) , 119.779(4) d , EC , ⁷⁵As , 5/2+ , , , - , ⁷⁶Se , style="text-align:right" , 34 , style="text-align:right" , 42 , 75.9192136(18) , colspan=3 align=center, Stable , 0+ , 0.0937(29) , , - , ⁷⁷Se , style="text-align:right" , 34 , style="text-align:right" , 43 , 76.9199140(18) , colspan=3 align=center, Stable , 1/2− , 0.0763(16) , , - , style="text-indent:1em" , ^77mSe , colspan="3" style="text-indent:2em" , 161.9223(7) keV , 17.36(5) s , IT , ⁷⁷Se , 7/2+ , , , - , ⁷⁸Se , style="text-align:right" , 34 , style="text-align:right" , 44 , 77.9173091(18) , colspan=3 align=center, Stable , 0+ , 0.2377(28) , , - , ⁷⁹Se

Long-lived fission product Long-lived fission products (LLFPs) are radioactive materials with a long half-life (more than 200,000 years) produced by nuclear fission of uranium and plutonium. Because of their persistent radiotoxicity it is necessary to isolate them from man ...

, style="text-align:right" , 34 , style="text-align:right" , 45 , 78.9184991(18) , 3.27(8)×10⁵ y , β⁻ , ⁷⁹Br , 7/2+ , , , - , rowspan=2 style="text-indent:1em" , ^79mSe , rowspan=2 colspan="3" style="text-indent:2em" , 95.77(3) keV , rowspan=2, 3.92(1) min , IT (99.944%) , ⁷⁹Se , rowspan=2, 1/2− , rowspan=2, , rowspan=2, , - , β⁻ (.056%) , ⁷⁹Br , - , ⁸⁰Se , style="text-align:right" , 34 , style="text-align:right" , 46 , 79.9165213(21) , colspan=3 align=center, Observationally StableBelieved to decay by β⁻β⁻ to ⁸⁰Kr , 0+ , 0.4961(41) , , - , ⁸¹Se , style="text-align:right" , 34 , style="text-align:right" , 47 , 80.9179925(22) , 18.45(12) min , β⁻ , ⁸¹Br , 1/2− , , , - , rowspan=2 style="text-indent:1em" , ^81mSe , rowspan=2 colspan="3" style="text-indent:2em" , 102.99(6) keV , rowspan=2, 57.28(2) min , IT (99.948%) , ⁸¹Se , rowspan=2, 7/2+ , rowspan=2, , rowspan=2, , - , β⁻ (.052%) , ⁸¹Br , - , ⁸²Se

Primordial Primordial may refer to: * Primordial era, an era after the Big Bang. See Chronology of the universe * Primordial sea (a.k.a. primordial ocean, ooze or soup). See Abiogenesis * Primordial nuclide, nuclides, a few radioactive, that formed before ...

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...

, style="text-align:right" , 34 , style="text-align:right" , 48 , 81.9166994(22) , 0.97(5)×10²⁰ y , β⁻β⁻ , ⁸²Kr , 0+ , 0.0873(22) , , - , ⁸³Se , style="text-align:right" , 34 , style="text-align:right" , 49 , 82.919118(4) , 22.3(3) min , β⁻ , ⁸³Br , 9/2+ , , , - , style="text-indent:1em" , ^83mSe , colspan="3" style="text-indent:2em" , 228.50(20) keV , 70.1(4) s , β⁻ , ⁸³Br , 1/2− , , , - , ⁸⁴Se , style="text-align:right" , 34 , style="text-align:right" , 50 , 83.918462(16) , 3.1(1) min , β⁻ , ⁸⁴Br , 0+ , , , - , ⁸⁵Se , style="text-align:right" , 34 , style="text-align:right" , 51 , 84.92225(3) , 31.7(9) s , β⁻ , ⁸⁵Br , (5/2+)# , , , - , ⁸⁶Se , style="text-align:right" , 34 , style="text-align:right" , 52 , 85.924272(17) , 15.3(9) s , β⁻ , ⁸⁶Br , 0+ , , , - , rowspan=2, ⁸⁷Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 53 , rowspan=2, 86.92852(4) , rowspan=2, 5.50(12) s , β⁻ (99.64%) , ⁸⁷Br , rowspan=2, (5/2+)# , rowspan=2, , rowspan=2, , - , β⁻, n (.36%) , ⁸⁶Br , - , rowspan=2, ⁸⁸Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 54 , rowspan=2, 87.93142(5) , rowspan=2, 1.53(6) s , β⁻ (99.01%) , ⁸⁸Br , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻, n (.99%) , ⁸⁷Br , - , rowspan=2, ⁸⁹Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 55 , rowspan=2, 88.93645(32)# , rowspan=2, 0.41(4) s , β⁻ (92.2%) , ⁸⁹Br , rowspan=2, (5/2+)# , rowspan=2, , rowspan=2, , - , β⁻, n (7.8%) , ⁸⁸Br , - , rowspan=2, ⁹⁰Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 56 , rowspan=2, 89.93996(43)# , rowspan=2, 300# ms 300 ns, β⁻, n , ⁸⁹Br , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻ , ⁹⁰Br , - , rowspan=2, ⁹¹Se , rowspan=2 style="text-align:right" , 34 , rowspan=2 style="text-align:right" , 57 , rowspan=2, 90.94596(54)# , rowspan=2, 270(50) ms , β⁻ (79%) , ⁹¹Br , rowspan=2, 1/2+# , rowspan=2, , rowspan=2, , - , β⁻, n , ⁹⁰Br , - , ⁹²Se , style="text-align:right" , 34 , style="text-align:right" , 58 , 91.94992(64)# , 100# ms 300 ns, β⁻ , ⁹²Br , 0+ , , , - , ⁹³Se , style="text-align:right" , 34 , style="text-align:right" , 59 , 92.95629(86)# , 50# ms 300 ns, , , 1/2+# , , , - , ⁹⁴Se , style="text-align:right" , 34 , style="text-align:right" , 60 , 93.96049(86)# , 20# ms 300 ns, , , 0+ , ,

Selenium-75

The isotope selenium-75 has radiopharmaceutical uses.

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Selenium Selenium