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 numb ...
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:
74Se,
76Se,
77Se,
78Se, and
80Se. The last three also occur as
fission products, 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](_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)
,
, -
,
79Se[ Long-lived fission product]
, 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]
, 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 ...
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, ...