Isotopes of thulium
Naturally occurring thulium (Tm) is composed of one stable isotope, Tm (100% natural abundance). Thirty-four radioisotopes have been characterized, with the most stable being Tm with a half-life of 1.92 years, Tm with a half-life of 128.6 days, Tm with a half-life of 93.1 days, and Tm with a half-life of 9.25 days. All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half-lives that are less than 2 minutes. This element also has 26 meta states, with the most  stable being Tm (t 5.1 minutes), Tm (t 74.5 seconds) and Tm (t 45 seconds). The isotopes of thulium range in atomic weight from 144.97007 u (Tm) to 178.95534 u (Tm). The primary decay mode before the most abundant stable isotope, Tm, is electron capture, and the primary mode after is beta emission. The primary decay products before Tm are erbium isotopes, and the primary products after are ytterbium isotopes. All isotopes of thulium are either radioactive or, in the case of Tm, observationally stable, meaning that Tm is predicted to be radioactive but no actual decay has been observed