(kăl'ĭfôr´´nēӘm) [from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900 degrees Celsius; b.p. about 1,470 degrees Celsius; 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).
Californium is a synthetic element ( atomic number = 98; relative atomic mass = 251; melting and boiling points unknown) that was...
(bûr'klēӘm) [from Berkeley], artificially produced radioactive chemical element; symbol Bk; at. no. 97; mass no. of most stable isotope 247; m.p. ab
(mĕndӘlāv'ēӘm), artificially produced radioactive chemical element; symbol Md; at. no. 101; mass no. of most stable isotope 258; m.p. 827 degrees Ce