Isotopes of cerium
Naturally occurring cerium is composed of 4 stable isotopes: 136Ce, 138Ce, 140Ce, and 142Ce, with 140Ce being the most abundant and the only one that is theoretically stable. The others, 136Ce, 138Ce, and 142Ce are predicted to undergo double [beta decay], which has never been observed. There are 35 radioisotopes that have been characterized, with the most stable being 144Ce, with a half-life of 284.89 days; 139Ce, with a half-life of 137.64 days and 141Ce, with a half-life of 32.505 days. All of the remaining radioactive isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than 10 minutes.
The known isotopes of cerium range from 121Ce to 157Ce, in addition to 14 meta states.