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 tellurium, ...
(
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 numbers) ...
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 weak ...
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
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 ato ...
of 327,000 years,
[The half-life of 79Se](_blank)
and
82Se, which has a very long half-life (~10
20 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 clos ...
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.
Th ...
[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)
,
, -
,
79SeLong-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)×10
5 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 Stable
[Believed 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 ]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)×10
20 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
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 tellurium, ...