Cerium-138

Main isotopes of cerium

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct 134Ce syn 3.16 d ε 134La 136Ce 0.186% stable 138Ce 0.251% stable 139Ce syn 137.640 d ε 139La 140Ce 88.449% stable 141Ce syn 32.501 d β− 141Pr 142Ce 11.114% stable 143Ce syn 33.039 d β− 143Pr 144Ce syn 284.893 d β− 144Pr
Standard atomic weight (Ar, standard)	140.116(1)

Naturally occurring cerium (₅₈Ce) is composed of 4 stable isotopes: ¹³⁶Ce, ¹³⁸Ce, ¹⁴⁰Ce, and ¹⁴²Ce, with ¹⁴⁰Ce being the most abundant (88.48% natural abundance) and the only one theoretically stable; ¹³⁶Ce, ¹³⁸Ce, and ¹⁴²Ce are predicted to undergo double beta decay but this process has never been observed. There are 35 radioisotopes that have been characterized, with the most stable being ¹⁴⁴Ce, with a half-life of 284.893 days; ¹³⁹Ce, with a half-life of 137.640 days and ¹⁴¹Ce, with a half-life of 32.501 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. This element also has 10 meta states.

The isotopes of cerium range in atomic weight from 119 u (¹¹⁹Ce) to 157 u (¹⁵⁷Ce).

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