# Isotopes of arsenic

Arsenic ($_{33}$As) has 32 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.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Isotopic abundance |
| Isotopic abundance |||
| $^{64}$As | 33 | 31 | 63.95756(22)# | 69.0(14) ms | β$^+$ | $^{64}$Ge | 0+# | |
| $^{64}$As | 33 | 31 | 63.95756(22)# | 69.0(14) ms | β$^+$, p? | $^{63}$Ga | 0+# | |
| $^{65}$As | 33 | 32 | 64.949611(91) | 130.3(6) ms | β$^+$ | $^{65}$Ge | 3/2−# | |
| $^{65}$As | 33 | 32 | 64.949611(91) | 130.3(6) ms | β$^+$, p? | $^{64}$Ga | 3/2−# | |
| $^{66}$As | 33 | 33 | 65.9441488(61) | 95.77(23) ms | β$^+$ | $^{66}$Ge | 0+ | |
| $^{66m1}$As | 1356.63(17) keV | 1356.63(17) keV | 1356.63(17) keV | 1.14(4) μs | IT | $^{66}$As | 5+ | |
| $^{66m2}$As | 3023.(3) keV | 3023.(3) keV | 3023.(3) keV | 7.98(26) μs | IT | $^{66}$As | 9+ | |
| $^{67}$As | 33 | 34 | 66.93925111(48) | 42.5(12) s | β$^+$ | $^{67}$Ge | (5/2−) | |
| $^{68}$As | 33 | 35 | 67.9367741(20) | 151.6(8) s | β$^+$ | $^{68}$Ge | 3+ | |
| $^{68m}$As | 425.1(2) keV | 425.1(2) keV | 425.1(2) keV | 111(20) ns | IT | $^{68}$As | 1+ | |
| $^{69}$As | 33 | 36 | 68.932246(34) | 15.2(2) min | β$^+$ | $^{69}$Ge | 5/2− | |
| $^{70}$As | 33 | 37 | 69.9309346(15) | 52.6(3) min | β$^+$ | $^{70}$Ge | 4+ | |
| $^{70m}$As | 32.046(23) keV | 32.046(23) keV | 32.046(23) keV | 96(3) μs | IT | $^{70}$As | 2+ | |
| $^{71}$As | 33 | 38 | 70.9271136(45) | 65.30(7) h | β$^+$ | $^{71}$Ge | 5/2− | |
| $^{72}$As | 33 | 39 | 71.9267523(44) | 26.0(1) h | β$^+$ | $^{72}$Ge | 2− | |
| $^{73}$As | 33 | 40 | 72.9238291(41) | 80.30(6) d | EC | $^{73}$Ge | 3/2− | |
| $^{73m}$As | 427.902(21) keV | 427.902(21) keV | 427.902(21) keV | 5.7(2) μs | IT | $^{73}$As | 9/2+ | |
| $^{74}$As | 33 | 41 | 73.9239286(18) | 17.77(2) d | β$^+$ (66%) | $^{74}$Ge | 2− | |
| $^{74}$As | 33 | 41 | 73.9239286(18) | 17.77(2) d | β$^−$ (34%) | $^{74}$Se | 2− | |
| $^{75}$As | 33 | 42 | 74.92159456(95) | Stable | Stable | Stable | 3/2− | 1.0000 |
| $^{75m}$As | 303.9243(8) keV | 303.9243(8) keV | 303.9243(8) keV | 17.62(23) ms | IT | $^{75}$As | 9/2+ | |
| $^{76}$As | 33 | 43 | 75.92239201(95) | 1.0933(38) d | β$^−$ | $^{76}$Se | 2− | |
| $^{76m}$As | 44.425(1) keV | 44.425(1) keV | 44.425(1) keV | 1.84(6) μs | IT | $^{76}$As | (1)+ | |
| $^{77}$As | 33 | 44 | 76.9206476(18) | 38.79(5) h | β$^−$ | $^{77}$Se | 3/2− | |
| $^{77m}$As | 475.48(4) keV | 475.48(4) keV | 475.48(4) keV | 114.0(25) μs | IT | $^{77}$As | 9/2+ | |
| $^{78}$As | 33 | 45 | 77.921828(10) | 90.7(2) min | β$^−$ | $^{78}$Se | 2− | |
| $^{79}$As | 33 | 46 | 78.9209484(57) | 9.01(15) min | β$^−$ | $^{79}$Se | 3/2− | |
| $^{79m}$As | 772.81(6) keV | 772.81(6) keV | 772.81(6) keV | 1.21(1) μs | IT | $^{79}$As | (9/2)+ | |
| $^{80}$As | 33 | 47 | 79.9224744(36) | 15.2(2) s | β$^−$ | $^{80}$Se | 1+ | |
| $^{81}$As | 33 | 48 | 80.9221323(28) | 33.3(8) s | β$^−$ | $^{81}$Se | 3/2− | |
| $^{82}$As | 33 | 49 | 81.9247387(40) | 19.1(5) s | β$^−$ | $^{82}$Se | (2−) | |
| $^{82m}$As | 131.6(5) keV | 131.6(5) keV | 131.6(5) keV | 13.6(4) s | β$^−$ | $^{82}$Se | (5-) | |
| $^{83}$As | 33 | 50 | 82.9252069(30) | 13.4(4) s | β$^−$ | $^{83}$Se | 5/2−# | |
| $^{84}$As | 33 | 51 | 83.9293033(34) | 3.16(58) s | β$^−$ (99.72%) | $^{84}$Se | (2−) | |
| $^{84}$As | 33 | 51 | 83.9293033(34) | 3.16(58) s | β$^−$, n (.28%) | $^{83}$Se | (2−) | |
| $^{85}$As | 33 | 52 | 84.9321637(33) | 2.022(7) s | β$^−$, n (62.6%) | $^{84}$Se | (5/2−) | |
| $^{85}$As | 33 | 52 | 84.9321637(33) | 2.022(7) s | β$^−$ (37.4%) | $^{85}$Se | (5/2−) | |
| $^{86}$As | 33 | 53 | 85.9367015(37) | 945(8) ms | β$^−$ (64.5%) | $^{86}$Se | (1−,2−) | |
| $^{86}$As | 33 | 53 | 85.9367015(37) | 945(8) ms | β$^−$, n (35.5%) | $^{85}$Se | (1−,2−) | |
| $^{86}$As | 33 | 53 | 85.9367015(37) | 945(8) ms | β$^−$, 2n? | $^{84}$Se | (1−,2−) | |
| $^{87}$As | 33 | 54 | 86.9402917(32) | 492(25) ms | β$^−$ (84.6%) | $^{87}$Se | (5/2−,3/2−) | |
| $^{87}$As | 33 | 54 | 86.9402917(32) | 492(25) ms | β$^−$, n (15.4%) | $^{86}$Se | (5/2−,3/2−) | |
| $^{87}$As | 33 | 54 | 86.9402917(32) | 492(25) ms | β$^−$, 2n? | $^{85}$Se | (5/2−,3/2−) | |
| $^{88}$As | 33 | 55 | 87.94584(22)# | 270(150) ms | β$^−$ | $^{88}$Se | | |
| $^{88}$As | 33 | 55 | 87.94584(22)# | 270(150) ms | β$^−$, n? | $^{87}$Se | | |
| $^{89}$As | 33 | 56 | 88.95005(32)# | 220# ms [>150 ns] | β$^−$? | $^{89}$Se | 5/2−# | |
| $^{89}$As | 33 | 56 | 88.95005(32)# | 220# ms [>150 ns] | β$^−$, n? | $^{88}$Se | 5/2−# | |
| $^{89}$As | 33 | 56 | 88.95005(32)# | 220# ms [>150 ns] | β$^−$, 2n? | $^{87}$Se | 5/2−# | |
| $^{90}$As | 33 | 57 | 89.95600(43)# | 70# ms [>300 ns] | β$^−$? | $^{90}$Se | | |
| $^{90}$As | 33 | 57 | 89.95600(43)# | 70# ms [>300 ns] | β$^−$, n? | $^{89}$Se | | |
| $^{90}$As | 33 | 57 | 89.95600(43)# | 70# ms [>300 ns] | β$^−$, 2n? | $^{88}$Se | | |
| $^{90m}$As | 124.5(5) keV | 124.5(5) keV | 124.5(5) keV | 220(100) ns | IT | $^{90}$As | | |
| $^{91}$As | 33 | 58 | 90.96082(43)# | 100# ms [>300 ns] | β$^−$? | $^{91}$Se | 5/2−# | |
| $^{91}$As | 33 | 58 | 90.96082(43)# | 100# ms [>300 ns] | β$^−$, n? | $^{90}$Se | 5/2−# | |
| $^{91}$As | 33 | 58 | 90.96082(43)# | 100# ms [>300 ns] | β$^−$, 2n? | $^{89}$Se | 5/2−# | |
| $^{92}$As | 33 | 59 | 91.96739(54)# | 45# ms [>300 ns] | β$^−$? | $^{92}$Se | | |
| $^{92}$As | 33 | 59 | 91.96739(54)# | 45# ms [>300 ns] | β$^−$, n? | $^{91}$Se | | |
| $^{92}$As | 33 | 59 | 91.96739(54)# | 45# ms [>300 ns] | β$^−$, 2n? | $^{90}$Se | | |
| $^{93}$As | 33 | 60 | | | | | | |
| $^{94}$As | 33 | 61 | | | | | | |
| $^{95}$As | 33 | 62 | | | | | | |
| This table header & footer: view |||||||||
* ↑ $^m$As – 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).