Isotopes of arsenic

Arsenic occurs naturally as one stable isotope, ⁷⁵As, so is monoisotopic and mononuclidic. Synthetic radioisotopes are known from ⁶⁴As to ⁹⁵As, as well as at least 11 isomers.

The most stable of these are ⁷³As with a half-life of 80.30 days and ⁷⁴As with a half-life of 17.77 days, followed by ⁷¹As (65.30 hours), ⁷⁷As (38.79 hours), ⁷⁶As (26.24 hours), and ⁷²As (26.0 hours). All others outside this range of mass number 71-77 have half-lives under 100 minutes and most under one minute. The longest-lived of the isomers is ^82mAs at 13.6 seconds.

Isotopes lighter than the stable one generally decay by positron emission or electron capture to germanium isotopes, while those heavier beta decay to selenium isotopes. A notable exception is that ⁷⁴As decays both ways.

List of isotopes

|-id=Arsenic-63 | ⁶³As | style="text-align:right" | 33 | style="text-align:right" | 30 | | | | | | |-id=Arsenic-64 | rowspan=2 |⁶⁴As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 31 | rowspan=2 |63.95756(22)# | rowspan=2 |69.0(14) ms | β⁺ | ⁶⁴Ge | rowspan=2 |0+# | rowspan=2 | |- | β⁺, p? | ⁶³Ga |-id=Arsenic-65 | rowspan=2 |⁶⁵As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 32 | rowspan=2 |64.949611(91) | rowspan=2 |130.3(6) ms | β⁺ | ⁶⁵Ge | rowspan=2 |3/2−# | rowspan=2 | |- | β⁺, p? | ⁶⁴Ga |-id=Arsenic-66 | ⁶⁶As | style="text-align:right" | 33 | style="text-align:right" | 33 | 65.9441488(61) | 95.77(23) ms | β⁺ | ⁶⁶Ge | 0+ | |-id=Arsenic-66m1 | style="text-indent:1em" | ^66m1As | colspan="3" style="text-indent:2em" | 1356.63(17) keV | 1.14(4) ÃŽÂ¼s | IT | ⁶⁶As | 5+ | |-id=Arsenic-66m2 | style="text-indent:1em" | ^66m2As | colspan="3" style="text-indent:2em" | 3023.(3) keV | 7.98(26) ÃŽÂ¼s | IT | ⁶⁶As | 9+ | |-id=Arsenic-67 | ⁶⁷As | style="text-align:right" | 33 | style="text-align:right" | 34 | 66.93925111(48) | 42.5(12) s | β⁺ | ⁶⁷Ge | (5/2−) | |-id=Arsenic-68 | ⁶⁸As | style="text-align:right" | 33 | style="text-align:right" | 35 | 67.9367741(20) | 151.6(8) s | β⁺ | ⁶⁸Ge | 3+ | |-id=Arsenic-68m | style="text-indent:1em" | ^68mAs | colspan="3" style="text-indent:2em" | 425.1(2) keV | 111(20) ns | IT | ⁶⁸As | 1+ | |-id=Arsenic-69 | ⁶⁹As | style="text-align:right" | 33 | style="text-align:right" | 36 | 68.932246(34) | 15.2(2) min | β⁺ | ⁶⁹Ge | 5/2− | |-id=Arsenic-70 | ⁷⁰As | style="text-align:right" | 33 | style="text-align:right" | 37 | 69.9309346(15) | 52.6(3) min | β⁺ | ⁷⁰Ge | 4+ | |-id=Arsenic-70m | style="text-indent:1em" | ^70mAs | colspan="3" style="text-indent:2em" | 32.046(23) keV | 96(3) ÃŽÂ¼s | IT | ⁷⁰As | 2+ | |-id=Arsenic-71 | ⁷¹As | style="text-align:right" | 33 | style="text-align:right" | 38 | 70.9271136(45) | 65.30(7) h | β⁺ | ⁷¹Ge | 5/2− | |-id=Arsenic-72 | ⁷²As | style="text-align:right" | 33 | style="text-align:right" | 39 | 71.9267523(44) | 26.0(1) h | β⁺ | ⁷²Ge | 2− | |-id=Arsenic-73 | ⁷³As | style="text-align:right" | 33 | style="text-align:right" | 40 | 72.9238291(41) | 80.30(6) d | EC | ⁷³Ge | 3/2− | |-id=Arsenic-73m | style="text-indent:1em" | ^73mAs | colspan="3" style="text-indent:2em" | 427.902(21) keV | 5.7(2) ÃŽÂ¼s | IT | ⁷³As | 9/2+ | |-id=Arsenic-74 | rowspan=2|⁷⁴As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 41 | rowspan=2|73.9239286(18) | rowspan=2|17.77(2) d | β⁺ (66%) | ⁷⁴Ge | rowspan=2|2− | rowspan=2| |- | β^− (34%) | ⁷⁴Se |-id=Arsenic-75 | ⁷⁵As | style="text-align:right" | 33 | style="text-align:right" | 42 | 74.92159456(95) | colspan=3 align=center|Stable | 3/2− | 1.0000 |-id=Arsenic-75m | style="text-indent:1em" | ^75mAs | colspan="3" style="text-indent:2em" | 303.9243(8) keV | 17.62(23) ms | IT | ⁷⁵As | 9/2+ | |-id=Arsenic-76 | ⁷⁶As | style="text-align:right" | 33 | style="text-align:right" | 43 | 75.92239201(95) | 1.0933(38) d | β^− | ⁷⁶Se | 2− | |-id=Arsenic-76m | style="text-indent:1em" | ^76mAs | colspan="3" style="text-indent:2em" | 44.425(1) keV | 1.84(6) ÃŽÂ¼s | IT | ⁷⁶As | (1)+ | |-id=Arsenic-77 | ⁷⁷As | style="text-align:right" | 33 | style="text-align:right" | 44 | 76.9206476(18) | 38.79(5) h | β^− | ⁷⁷Se | 3/2− | |-id=Arsenic-77m | style="text-indent:1em" | ^77mAs | colspan="3" style="text-indent:2em" | 475.48(4) keV | 114.0(25) ÃŽÂ¼s | IT | ⁷⁷As | 9/2+ | |-id=Arsenic-78 | ⁷⁸As | style="text-align:right" | 33 | style="text-align:right" | 45 | 77.921828(10) | 90.7(2) min | β^− | ⁷⁸Se | 2− | |-id=Arsenic-79 | ⁷⁹As | style="text-align:right" | 33 | style="text-align:right" | 46 | 78.9209484(57) | 9.01(15) min | β^− | ⁷⁹Se | 3/2− | |-id=Arsenic-79m | style="text-indent:1em" | ^79mAs | colspan="3" style="text-indent:2em" | 772.81(6) keV | 1.21(1) ÃŽÂ¼s | IT | ⁷⁹As | (9/2)+ | |-id=Arsenic-80 | ⁸⁰As | style="text-align:right" | 33 | style="text-align:right" | 47 | 79.9224744(36) | 15.2(2) s | β^− | ⁸⁰Se | 1+ | |-id=Arsenic-81 | ⁸¹As | style="text-align:right" | 33 | style="text-align:right" | 48 | 80.9221323(28) | 33.3(8) s | β^− | ⁸¹Se | 3/2− | |-id=Arsenic-82 | ⁸²As | style="text-align:right" | 33 | style="text-align:right" | 49 | 81.9247387(40) | 19.1(5) s | β^− | ⁸²Se | (2−) | |-id=Arsenic-82m | style="text-indent:1em" | ^82mAs | colspan="3" style="text-indent:2em" | 131.6(5) keV | 13.6(4) s | β^− | ⁸²Se | (5-) | |-id=Arsenic-83 | ⁸³As | style="text-align:right" | 33 | style="text-align:right" | 50 | 82.9252069(30) | 13.4(4) s | β^− | ⁸³Se | 5/2−# | |-id=Arsenic-84 | rowspan=2|⁸⁴As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 51 | rowspan=2|83.9293033(34) | rowspan=2|3.16(58) s | β^− (99.72%) | ⁸⁴Se | rowspan=2|(2−) | rowspan=2| |- | β^−, n (.28%) | ⁸³Se |-id=Arsenic-85 | rowspan=2|⁸⁵As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 52 | rowspan=2|84.9321637(33) | rowspan=2|2.022(7) s | β^−, n (62.6%) | ⁸⁴Se | rowspan=2|(5/2−) | rowspan=2| |- | β^− (37.4%) | ⁸⁵Se |-id=Arsenic-86 | rowspan=3|⁸⁶As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 53 | rowspan=3|85.9367015(37) | rowspan=3|945(8) ms | β^− (64.5%) | ⁸⁶Se | rowspan=3|(1−,2−) | rowspan=3| |- | β^−, n (35.5%) | ⁸⁵Se |- | β^−, 2n? | ⁸⁴Se |-id=Arsenic-87 | rowspan=3|⁸⁷As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 54 | rowspan=3|86.9402917(32) | rowspan=3|492(25) ms | β^− (84.6%) | ⁸⁷Se | rowspan=3|(5/2−,3/2−) | rowspan=3| |- | β^−, n (15.4%) | ⁸⁶Se |- | β^−, 2n? | ⁸⁵Se |-id=Arsenic-88 | rowspan=2|⁸⁸As | rowspan=2 style="text-align:right" | 33 | rowspan=2 style="text-align:right" | 55 | rowspan=2|87.94584(22)# | rowspan=2|270(150) ms | β^− | ⁸⁸Se | rowspan=2| | rowspan=2| |- | β^−, n? | ⁸⁷Se |-id=Arsenic-89 | rowspan=3|⁸⁹As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 56 | rowspan=3|88.95005(32)# | rowspan=3|220# ms [>150 ns] | β^−? | ⁸⁹Se | rowspan=3|5/2−# | rowspan=3| |- | β^−, n? | ⁸⁸Se |- | β^−, 2n? | ⁸⁷Se |-id=Arsenic-90 | rowspan=3|⁹⁰As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 57 | rowspan=3|89.95600(43)# | rowspan=3|70# ms [>300 ns] | β^−? | ⁹⁰Se | rowspan=3| | rowspan=3| |- | β^−, n? | ⁸⁹Se |- | β^−, 2n? | ⁸⁸Se |-id=Arsenic-90m | style="text-indent:1em" | ^90mAs | colspan="3" style="text-indent:2em" | 124.5(5) keV | 220(100) ns | IT | ⁹⁰As | | |-id=Arsenic-91 | rowspan=3|⁹¹As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 58 | rowspan=3|90.96082(43)# | rowspan=3|100# ms [>300 ns] | β^−? | ⁹¹Se | rowspan=3|5/2−# | rowspan=3| |- | β^−, n? | ⁹⁰Se |- | β^−, 2n? | ⁸⁹Se |-id=Arsenic-92 | rowspan=3|⁹²As | rowspan=3 style="text-align:right" | 33 | rowspan=3 style="text-align:right" | 59 | rowspan=3|91.96739(54)# | rowspan=3|45# ms [>300 ns] | β^−? | ⁹²Se | rowspan=3| | rowspan=3| |- | β^−, n? | ⁹¹Se |- | β^−, 2n? | ⁹⁰Se |-id=Arsenic-93 | ⁹³As | style="text-align:right" | 33 | style="text-align:right" | 60 | | | | | | |-id=Arsenic-94 | ⁹⁴As | style="text-align:right" | 33 | style="text-align:right" | 61 | | | | | | |-id=Arsenic-95 | ⁹⁵As | style="text-align:right" | 33 | style="text-align:right" | 62 | | | | | |

See also

Daughter products other than arsenic

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

References

• A.Shore, A. Fritsch, M. Heim, A. Schuh, M. Thoennessen. Discovery of the Arsenic Isotopes. arXiv:0902.4361.