Selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and telluriu ...

(₃₄Se) has six natural

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass number ...

s that occur in significant quantities, along with the trace isotope ⁷⁹Se, which occurs in minute quantities in

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly ...

ores. Five of these isotopes are stable: 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 relea ...

, along with ⁷⁹Se, which has a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

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 In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move clo ...

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 Stable Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. T ...

Believed 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 Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which is ...

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