Erbium-166

Main isotopes of erbium

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct 160Er syn 28.58 h ε 160Ho 162Er 0.139% stable 164Er 1.601% stable 165Er syn 10.36 h ε 165Ho 166Er 33.503% stable 167Er 22.869% stable 168Er 26.978% stable 169Er syn 9.4 d β− 169Tm 170Er 14.910% stable 171Er syn 7.516 h β− 171Tm 172Er syn 49.3 h β− 172Tm
Standard atomic weight (Ar)	7002167259000000000♠167.259(3)

Naturally occurring erbium (₆₈Er) is composed of 6 stable isotopes, with ¹⁶⁶Er being the most abundant (33.503% natural abundance). Thirty radioisotopes have been characterized with between 74 and 108 neutrons, or 142 to 177 nucleons, with the most stable being ¹⁶⁹Er with a half-life of 9.4 days, ¹⁷²Er with a half-life of 49.3 hours, ¹⁶⁰Er with a half-life of 28.58 hours, ¹⁶⁵Er with a half-life of 10.36 hours, and ¹⁷¹Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has 13 meta states, with the most stable being ^167mEr (t_1/2 2.269 seconds).

The isotopes of erbium range in atomic weight from 141.9723 u (¹⁴²Er) to 176.9541 u (¹⁷⁷Er). The primary decay mode before the most abundant stable isotope, ¹⁶⁶Er, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁶⁶Er are holmium isotopes, and the primary products after are thulium isotopes.

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