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 74As synth 17.8 d β+66% 74Ge β−34% 74Se 75As 100% stable
Standard atomic weight Ar°(As)
	74.921595±0.000006[2] 74.922±0.001 (abridged)[3]
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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]	Isotopic abundance
	Excitation energy[n 8]
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[n 9]	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: view

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).
9. Fission product

See also

Daughter products other than arsenic

• Isotopes of selenium
• Isotopes of germanium
• Isotopes of gallium