Isotopes of arsenic

Arsenic (33As) has 32 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 with a half-life of 80 days.

Isotopes of arsenic (33As)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
73As synth 80.3 d ε 73Ge
γ –
74As synth 17.8 d ε 74Ge
β+ 74Ge
γ –
β− 74Se
75As 100% stable
Standard atomic weight Ar°(As)

List of isotopes
Nuclide
[n 1]		 Z N Isotopic mass (Da)[4]
[n 2][n 3]		 Half-life[1]
 Decay
mode[1]
[n 4]		 Daughter
isotope
[n 5][n 6]		 Spin and
parity[1]
[n 7][n 8]		 Natural abundance (mole fraction)
Excitation energy[n 8] Normal proportion[1] Range of variation
64As 33 31 63.95756(22)# 69.0(14) ms β+ 64Ge 0+#
β+, p? 63Ga
65As 33 32 64.949611(91) 130.3(6) ms β+ 65Ge 3/2−#
β+, p? 64Ga
66As 33 33 65.9441488(61) 95.77(23) ms β+ 66Ge 0+
66m1As 1356.63(17) keV 1.14(4) μs IT 66As 5+
66m2As 3023.(3) keV 7.98(26) μs IT 66As 9+
67As 33 34 66.93925111(48) 42.5(12) s β+ 67Ge (5/2−)
68As 33 35 67.9367741(20) 151.6(8) s β+ 68Ge 3+
68mAs 425.1(2) keV 111(20) ns IT 68As 1+
69As 33 36 68.932246(34) 15.2(2) min β+ 69Ge 5/2−
70As 33 37 69.9309346(15) 52.6(3) min β+ 70Ge 4+
70mAs 32.046(23) keV 96(3) μs IT 70As 2+
71As 33 38 70.9271136(45) 65.30(7) h β+ 71Ge 5/2−
72As 33 39 71.9267523(44) 26.0(1) h β+ 72Ge 2−
73As 33 40 72.9238291(41) 80.30(6) d EC 73Ge 3/2−
73mAs 427.902(21) keV 5.7(2) μs IT 73As 9/2+
74As 33 41 73.9239286(18) 17.77(2) d β+ (66%) 74Ge 2−
β− (34%) 74Se
75As 33 42 74.92159456(95) Stable 3/2− 1.0000
75mAs 303.9243(8) keV 17.62(23) ms IT 75As 9/2+
76As 33 43 75.92239201(95) 1.0933(38) d β− 76Se 2−
76mAs 44.425(1) keV 1.84(6) μs IT 76As (1)+
77As 33 44 76.9206476(18) 38.79(5) h β− 77Se 3/2−
77mAs 475.48(4) keV 114.0(25) μs IT 77As 9/2+
78As 33 45 77.921828(10) 90.7(2) min β− 78Se 2−
79As 33 46 78.9209484(57) 9.01(15) min β− 79Se 3/2−
79mAs 772.81(6) keV 1.21(1) μs IT 79As (9/2)+
80As 33 47 79.9224744(36) 15.2(2) s β− 80Se 1+
81As 33 48 80.9221323(28) 33.3(8) s β− 81Se 3/2−
82As 33 49 81.9247387(40) 19.1(5) s β− 82Se (2−)
82mAs 131.6(5) keV 13.6(4) s β− 82Se (5-)
83As 33 50 82.9252069(30) 13.4(4) s β− 83Se 5/2−#
84As 33 51 83.9293033(34) 3.16(58) s β− (99.72%) 84Se (2−)
β−, n (.28%) 83Se
85As 33 52 84.9321637(33) 2.022(7) s β−, n (62.6%) 84Se (5/2−)
β− (37.4%) 85Se
86As 33 53 85.9367015(37) 945(8) ms β− (64.5%) 86Se (1−,2−)
β−, n (35.5%) 85Se
β−, 2n? 84Se
87As 33 54 86.9402917(32) 492(25) ms β− (84.6%) 87Se (5/2−,3/2−)
β−, n (15.4%) 86Se
β−, 2n? 85Se
88As 33 55 87.94584(22)# 270(150) ms β− 88Se
β−, n? 87Se
89As 33 56 88.95005(32)# 220# ms [>150 ns] β−? 89Se 5/2−#
β−, n? 88Se
β−, 2n? 87Se
90As 33 57 89.95600(43)# 70# ms [>300 ns] β−? 90Se
β−, n? 89Se
β−, 2n? 88Se
90mAs 124.5(5) keV 220(100) ns IT 90As
91As 33 58 90.96082(43)# 100# ms [>300 ns] β−? 91Se 5/2−#
β−, n? 90Se
β−, 2n? 89Se
92As 33 59 91.96739(54)# 45# ms [>300 ns] β−? 92Se
β−, n? 91Se
β−, 2n? 90Se
93As[5] 33 60
94As[5] 33 61
95As[5] 33 62
This table header & footer:
  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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

References
  1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. "Standard Atomic Weights: Arsenic". CIAAW. 2013.
  3. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  5. Shimizu, Y.; Kubo, T.; Sumikama, T.; Fukuda, N.; Takeda, H.; Suzuki, H.; Ahn, D. S.; Inabe, N.; Kusaka, K.; Ohtake, M.; Yanagisawa, Y.; Yoshida, K.; Ichikawa, Y.; Isobe, T.; Otsu, H.; Sato, H.; Sonoda, T.; Murai, D.; Iwasa, N.; Imai, N.; Hirayama, Y.; Jeong, S. C.; Kimura, S.; Miyatake, H.; Mukai, M.; Kim, D. G.; Kim, E.; Yagi, A. (8 April 2024). "Production of new neutron-rich isotopes near the N = 60 isotones Ge 92 and As 93 by in-flight fission of a 345 MeV/nucleon U 238 beam". Physical Review C. 109 (4). doi:10.1103/PhysRevC.109.044313.
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