californium

californium [from California ], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900°C; b.p. about 1,470°C; density unknown; valence +3. Californium is a member of the actinide series of chemical elements, found in Group 3 of the periodic table . Its chemical properties are similar to those of lanthanum . Eighteen isotopes of californium are known, with half-lives ranging from about 40 sec for californium-239 to about 900 years for californium-251, the most stable isotope. Californium-249 (half-life 351 years) is most useful for chemical investigations; it is obtained by the decay of berkelium-249. Four solid compounds of californium have been prepared; they are the trichloride, oxychloride, oxyfluoride, and oxide. Californium-252 (half-life 2.6 years) is produced in nuclear reactors for use as a source of neutrons for counters and electronic systems in industrial and medical applications. The sixth transuranium element to be synthesized, californium has yet to be found in the earth's crust. Californium was first produced in 1950 by Glenn T. Seaborg , Stanley G. Thompson, Albert Ghiorso, and Kenneth Street, Jr., in a cyclotron at the Univ. of California at Berkeley by bombarding curium-242 with alpha particles, resulting in californium-245 (half-life 45 min).

cal·i·for·ni·um / ˌkaləˈfôrnēəm/ • n. the chemical element of atomic number 98, a radioactive metal of the actinide series. (Symbol: Cf)

californium (symbol Cf) Radioactive metallic element of the actinide series, first made in 1950 by US nuclear chemist Glenn Seaborg (1912–99) and colleagues at the University of California, Berkeley, by alpha-particle bombardment of the curium isotope Cm²⁴². Californium presents biological dangers because one microgram releases 170 million neutrons a minute. Properties: at.no. 98; most stable isotope Cf²⁵¹ (half-life 800 yr). See also transuranic elements