The atomic mass of Cerium is 140.12 . The Chemical symbol of Cerium is Ce and it is a member of the Lanthanide group . Other compounds include cerium ( III ) carbonate ( Ce2 ( CO3 ) 3 ) , cerium ( III ) fluoride ( CeF3 ) , cerium ( III ) oxide ( Ce2O3 ) , as well as cerium ( IV ) sulfate ( ceric sulfate , Ce ( SO4 ) 2 ) and cerium ( III ) triflate ( Ce ( OSO2CF3 ) 3 ) .