Isotopes of Lanthanum

Isotopes Of Lanthanum

Naturally occurring lanthanum (La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). 38 radioisotopes have been characterized with the most stable being 138La with a half-life of 102×109 years, 137La with a half-life of 60,000 years and 140La with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 minute. This element also has 12 nuclear isomers, the longest-lived of which is 132mLa with a half-life of 24.3 minutes.

The isotopes of lanthanum range in atomic weight from 116.95 u (117La) to 154.96 u (155La).

Standard atomic mass: 138.90547(7) u