Stable Cerium Isotopes - Ce Isotopes | Nominal mass | Accurate mass | % Natural abundance | Chemical form | Enrichment available % | | 136Ce | 135.907140 (50) | 0.19 (2) | oxide | 21 - 53+ | | 138Ce | 137.905985 (12) | 0.25 (2) | oxide, oxelate | 12 - 41+ | | 140Ce | 139.905433 (4) | 88.45 (51) | oxide | 99+ | | 142Ce | 141.909241 (4) | 11.114 (51) | oxide | 93 - 95+ | |