Isotopes of arsenic
# Isotopes of arsenic

Arsenic $(_{33}As)$ has 33 known isotopes and at least 10 isomers. Only one of these isotopes, $^{75}As,$ is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is $^{73}As$ with 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 $^{75}As,$ irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope $^{76}As$ 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. Such a weapon is not known to have ever been built, tested, or used.

Transmutation of arsenic to much less toxic selenium could prevent cycling of arsenic, from groundwater to waterways to oceans and back via Sargassum seaweeds. Bioremediation can provide a large supply of arsenic and rid aquifers of persistent poisoning issues.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (mole fraction) | Natural abundance (mole fraction) |
| - | - | - | - | - | - | - | - | - | - |
| Nuclide | Excitation energy | Excitation energy | Excitation energy | Half-life | Decay mode | Daughter isotope | Spin and parity | Normal proportion | Range of variation |
| $^{60}As$ | 33 | 27 | 59.99313(64)# | | p | $^{59}Ge$ | 5+# | | |
| $^{61}As$ | 33 | 28 | 60.98062(64)# | | p | $^{60}Ge$ | 3/2−# | | |
| $^{62}As$ | 33 | 29 | 61.97320(32)# | | p | $^{61}Ge$ | 1+# | | |
| $^{63}As$ | 33 | 30 | 62.96369(54)# | | p | $^{62}Ge$ | (3/2−)# | | |
| $^{64}As$ | 33 | 31 | 63.95757(38)# | 40(30) ms [18(+43-7) ms] | $β^+$ | $^{64}Ge$ | 0+# | | |
| $^{65}As$ | 33 | 32 | 64.94956(32)# | 170(30) ms | $β^+$ | $^{65}Ge$ | 3/2−# | | |
| $^{66}As$ | 33 | 33 | 65.94471(73) | 95.77(23) ms | $β^+$ | $^{66}Ge$ | (0+) | | |
| $^{66m1}As$ | 1356.70(17) keV | 1356.70(17) keV | 1356.70(17) keV | 1.1(1) µs | | | (5+) | | |
| $^{66m2}As$ | 3023.9(3) keV | 3023.9(3) keV | 3023.9(3) keV | 8.2(5) µs | | | (9+) | | |
| $^{67}As$ | 33 | 34 | 66.93919(11) | 42.5(12) s | $β^+$ | $^{67}Ge$ | (5/2−) | | |
| $^{68}As$ | 33 | 35 | 67.93677(5) | 151.6(8) s | $β^+$ | $^{68}Ge$ | 3+ | | |
| $^{68m}As$ | 425.21(16) keV | 425.21(16) keV | 425.21(16) keV | 111(20) ns [?107(+23-16) ns] | | | 1+ | | |
| $^{69}As$ | 33 | 36 | 68.93227(3) | 15.2(2) min | $β^+$ | $^{69}Ge$ | 5/2− | | |
| $^{70}As$ | 33 | 37 | 69.93092(5) | 52.6(3) min | $β^+$ | $^{70}Ge$ | 4(+#) | | |
| $^{70m}As$ | 32.008(23) keV | 32.008(23) keV | 32.008(23) keV | 96(3) µs | | | 2(+) | | |
| $^{71}As$ | 33 | 38 | 70.927112(5) | 65.28(15) h | $β^+$ | $^{71}Ge$ | 5/2− | | |
| $^{72}As$ | 33 | 39 | 71.926752(5) | 26.0(1) h | $β^+$ | $^{72}Ge$ | 2− | | |
| $^{73}As$ | 33 | 40 | 72.923825(4) | 80.30(6) d | EC | $^{73}Ge$ | 3/2− | | |
| $^{74}As$ | 33 | 41 | 73.9239287(25) | 17.77(2) d | $β^+$ (66%) | $^{74}Ge$ | 2− | | |
| $^{74}As$ | 33 | 41 | 73.9239287(25) | 17.77(2) d | $β^−$ (34%) | $^{74}Se$ | 2− | | |
| $^{75}As$ | 33 | 42 | 74.9215965(20) | Stable | Stable | Stable | 3/2− | 1.0000 | |
| $^{75m}As$ | 303.9241(7) keV | 303.9241(7) keV | 303.9241(7) keV | 17.62(23) ms | | | 9/2+ | | |
| $^{76}As$ | 33 | 43 | 75.922394(2) | 1.0942(7) d | $β^−$ (99.98%) | $^{76}Se$ | 2− | | |
| $^{76}As$ | 33 | 43 | 75.922394(2) | 1.0942(7) d | EC (.02%) | $^{76}Ge$ | 2− | | |
| $^{76m}As$ | 44.425(1) keV | 44.425(1) keV | 44.425(1) keV | 1.84(6) µs | | | (1)+ | | |
| $^{77}As$ | 33 | 44 | 76.9206473(25) | 38.83(5) h | $β^−$ | $^{77m}Se$ | 3/2− | | |
| $^{77m}As$ | 475.443(16) keV | 475.443(16) keV | 475.443(16) keV | 114.0(25) µs | | | 9/2+ | | |
| $^{78}As$ | 33 | 45 | 77.921827(11) | 90.7(2) min | $β^−$ | $^{78}Se$ | 2− | | |
| $^{79}As$ | 33 | 46 | 78.920948(6) | 9.01(15) min | $β^−$ | $^{79m}Se$ | 3/2− | | |
| $^{79m}As$ | 772.81(6) keV | 772.81(6) keV | 772.81(6) keV | 1.21(1) µs | | | (9/2)+ | | |
| $^{80}As$ | 33 | 47 | 79.922534(25) | 15.2(2) s | $β^−$ | $^{80}Se$ | 1+ | | |
| $^{81}As$ | 33 | 48 | 80.922132(6) | 33.3(8) s | $β^−$ | $^{81m}Se$ | 3/2− | | |
| $^{82}As$ | 33 | 49 | 81.92450(21) | 19.1(5) s | $β^−$ | $^{82}Se$ | (1+) | | |
| $^{82m}As$ | 250(200) keV | 250(200) keV | 250(200) keV | 13.6(4) s | $β^−$ | $^{82}Se$ | (5-) | | |
| $^{83}As$ | 33 | 50 | 82.92498(24) | 13.4(3) s | $β^−$ | $^{83m}Se$ | 3/2−# | | |
| $^{84}As$ | 33 | 51 | 83.92906(32)# | 4.02(3) s | $β^−$ (99.721%) | $^{84}Se$ | (3)(+#) | | |
| $^{84}As$ | 33 | 51 | 83.92906(32)# | 4.02(3) s | $β^−,$ n (.279%) | $^{83}Se$ | (3)(+#) | | |
| $^{84m}As$ | 0(100)# keV | 0(100)# keV | 0(100)# keV | 650(150) ms | | | | | |
| $^{85}As$ | 33 | 52 | 84.93202(21)# | 2.021(10) s | $β^−,$ n (59.4%) | $^{84}Se$ | (3/2−)# | | |
| $^{85}As$ | 33 | 52 | 84.93202(21)# | 2.021(10) s | $β^−$ (40.6%) | $^{85}Se$ | (3/2−)# | | |
| $^{86}As$ | 33 | 53 | 85.93650(32)# | 0.945(8) s | $β^−$ (67%) | $^{86}Se$ | | | |
| $^{86}As$ | 33 | 53 | 85.93650(32)# | 0.945(8) s | $β^−,$ n (33%) | $^{85}Se$ | | | |
| $^{87}As$ | 33 | 54 | 86.93990(32)# | 0.56(8) s | $β^−$ (84.6%) | $^{87}Se$ | 3/2−# | | |
| $^{87}As$ | 33 | 54 | 86.93990(32)# | 0.56(8) s | $β^−,$ n (15.4%) | $^{86}Se$ | 3/2−# | | |
| $^{88}As$ | 33 | 55 | 87.94494(54)# | 300# ms [>300 ns] | $β^−$ | $^{88}Se$ | | | |
| $^{88}As$ | 33 | 55 | 87.94494(54)# | 300# ms [>300 ns] | $β^−,$ n | $^{87}Se$ | | | |
| $^{89}As$ | 33 | 56 | 88.94939(54)# | 200# ms [>300 ns] | $β^−$ | $^{89}Se$ | 3/2−# | | |
| $^{90}As$ | 33 | 57 | 89.95550(86)# | 80# ms [>300 ns] | | | | | |
| $^{91}As$ | 33 | 58 | 90.96043(97)# | 50# ms [>300 ns] | | | 3/2−# | | |
| $^{92}As$ | 33 | 59 | 91.96680(97)# | 30# ms [>300 ns] | | | | | |
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* ↑ $^mAs$ – Excited nuclear isomer.
* ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
* ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
* ↑ Modes of decay: EC:Electron capture n:Neutron emission p:Proton emission
* ↑ Bold italics symbol as daughter – Daughter product is nearly stable.
* ↑ Bold symbol as daughter – Daughter product is stable.
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
