A radioactive chemical element of the actinide series produced by intense neutron irradiation of plutonium or curium.

It was named (1950) by the discoverers, Glenn Theodoure Seaboeg and associates, at the University of California. Symbol Cf at wt. 251, at no.98 melt pt. 900° C, boiling pt 1472° C.

An isotope with a half life of 2.65 years is used as a neutron source in mining, medicine, etc.