This element also has numerous meta states, with the most stable being 167mEr (t1/2 = 2.269 seconds).
The isotopes of erbium range in atomic weight from 141.9723 u (142Er) to 179.9644 u (180Er).
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.
All isotopes of erbium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.