Isotopes of arsenic

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. Such a weapon is not known to have ever been built, tested, or used.

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 isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

References

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.

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.
• A.Shore, A. Fritsch, M. Heim, A. Schuh, M. Thoennessen. Discovery of the Arsenic Isotopes. arXiv:0902.4361.

External links