Isotopes of lanthanum

Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance).

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.

Lighter isotopes mostly decay to isotopes of barium and heavy ones mostly decay to isotopes of cerium.

The isotopes of lanthanum range in atomic weight from 115.96 u (116La) to 154.96 u (155La).