Isotopes of arsenic
Open-knowledge reference entry
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
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.
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