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Arsenic (33As) has 33 known isotopes and at least 10 isomers. Only one of these isotopes, 75As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73As has a half-life of 80 days. Arsenic has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 75As, irradiated by the intense highenergy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 76As with a half-life of 1.0778 days and produce approximately 1.13 MeV gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several hours.[citation needed] Such a weapon is not known to have ever been built, tested, or used.[citation needed]

Main isotopes of arsenic (33As)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
73As syn 80.3 d ε 73Ge
γ
74As syn 17.8 d ε 74Ge
β+ 74Ge
γ
β 74Se
75As 100% stable
Standard atomic weight Ar, standard(As)
  • 74.921595(6)[1]

List of isotopesEdit

Nuclide
[n 1]
Z N Isotopic mass (u)
[n 2][n 3]
Half-life
Decay
mode

[n 4]
Daughter
isotope

[n 5][n 6]
Spin and
parity
[n 7][n 8]
Natural abundance (mole fraction)
Excitation energy[n 8] Normal proportion Range of variation
60As 33 27 59.99313(64)# p 59Ge 5+#
61As 33 28 60.98062(64)# p 60Ge 3/2−#
62As 33 29 61.97320(32)# p 61Ge 1+#
63As 33 30 62.96369(54)# p 62Ge (3/2−)#
64As 33 31 63.95757(38)# 40(30) ms
[18(+43-7) ms]
β+ 64Ge 0+#
65As 33 32 64.94956(32)# 170(30) ms β+ 65Ge 3/2−#
66As 33 33 65.94471(73) 95.77(23) ms β+ 66Ge (0+)
66m1As 1356.70(17) keV 1.1(1) µs (5+)
66m2As 3023.9(3) keV 8.2(5) µs (9+)
67As 33 34 66.93919(11) 42.5(12) s β+ 67Ge (5/2−)
68As 33 35 67.93677(5) 151.6(8) s β+ 68Ge 3+
68mAs 425.21(16) keV 111(20) ns
[?107(+23-16) ns]
1+
69As 33 36 68.93227(3) 15.2(2) min β+ 69Ge 5/2−
70As 33 37 69.93092(5) 52.6(3) min β+ 70Ge 4(+#)
70mAs 32.008(23) keV 96(3) µs 2(+)
71As 33 38 70.927112(5) 65.28(15) h β+ 71Ge 5/2−
72As 33 39 71.926752(5) 26.0(1) h β+ 72Ge 2−
73As 33 40 72.923825(4) 80.30(6) d EC 73Ge 3/2−
74As 33 41 73.9239287(25) 17.77(2) d β+ (66%) 74Ge 2−
β (34%) 74Se
75As 33 42 74.9215965(20) Stable 3/2− 1.0000
75mAs 303.9241(7) keV 17.62(23) ms 9/2+
76As 33 43 75.922394(2) 1.0942(7) d β (99.98%) 76Se 2−
EC (.02%) 76Ge
76mAs 44.425(1) keV 1.84(6) µs (1)+
77As 33 44 76.9206473(25) 38.83(5) h β 77mSe 3/2−
77mAs 475.443(16) keV 114.0(25) µs 9/2+
78As 33 45 77.921827(11) 90.7(2) min β 78Se 2−
79As 33 46 78.920948(6) 9.01(15) min β 79mSe 3/2−
79mAs 772.81(6) keV 1.21(1) µs (9/2)+
80As 33 47 79.922534(25) 15.2(2) s β 80Se 1+
81As 33 48 80.922132(6) 33.3(8) s β 81mSe 3/2−
82As 33 49 81.92450(21) 19.1(5) s β 82Se (1+)
82mAs 250(200) keV 13.6(4) s β 82Se (5-)
83As 33 50 82.92498(24) 13.4(3) s β 83mSe 3/2−#
84As 33 51 83.92906(32)# 4.02(3) s β (99.721%) 84Se (3)(+#)
β, n (.279%) 83Se
84mAs 0(100)# keV 650(150) ms
85As 33 52 84.93202(21)# 2.021(10) s β, n (59.4%) 84Se (3/2−)#
β (40.6%) 85Se
86As 33 53 85.93650(32)# 0.945(8) s β (67%) 86Se
β, n (33%) 85Se
87As 33 54 86.93990(32)# 0.56(8) s β (84.6%) 87Se 3/2−#
β, n (15.4%) 86Se
88As 33 55 87.94494(54)# 300# ms
[>300 ns]
β 88Se
β, n 87Se
89As 33 56 88.94939(54)# 200# ms
[>300 ns]
β 89Se 3/2−#
90As 33 57 89.95550(86)# 80# ms
[>300 ns]
91As 33 58 90.96043(97)# 50# ms
[>300 ns]
3/2−#
92As 33 59 91.96680(97)# 30# ms
[>300 ns]
  1. ^ mAs – Excited nuclear isomer.
  2. ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ^ Modes of decay:
    EC: Electron capture


    n: Neutron emission
    p: Proton emission
  5. ^ Bold italics symbol as daughter – Daughter product is nearly stable.
  6. ^ Bold symbol as daughter – Daughter product is stable.
  7. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  8. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

ReferencesEdit

  1. ^ Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.

External linksEdit