Californium – Cf

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Title: Cf

Californium (Cf), synthetic chemical element of the actinoid series of the periodic table, atomic number 98. Not occurring in nature, californium (as the isotope californium-245) was discovered (1950) by American chemists Stanley G. Thompson, Kenneth Street, Jr., Albert Ghiorso, and Glenn T. Seaborg at the University of California, Berkeley, as a product resulting from the helium–ion bombardment of curium-242 (atomic number 96) in the 152-cm (60-inch) cyclotron, followed by chemical separation from other elements by chromatography. The element was named after the state of California, where it was discovered.

chemical properties of Californium (part of Periodic Table of the Elements imagemap) — Encyclopædia Britannica, Inc.

BRITANNICA QUIZ118 Names and Symbols of the Periodic Table QuizSr

All californium isotopes are radioactive; the long-lived isotopes are produced from berkelium-249 or from californium-249. They are californium-249 (351-year half-life), californium-250 (13-year half-life), californium-251 (898-year half-life), and californium-252 (2.645-year half-life). The isotope californium-249 has been used in tracer levels and microgram amounts to investigate the chemistry of californium (which exhibits an oxidation state of +3 in aqueous solution) and for preparing microgram quantities of compounds such as the oxychloride CfOCl, the oxides Cf₂O₃ and CfO₂, and the trichloride CfCl₃. The dihalides CfCl₂, CfBr₂, and CfI₂ have been made. There is also some evidence from electrochemical studies in solutions for a +2 state. Metallic californium has been prepared and is structurally similar to metallic americium, curium, berkelium, and most lanthanoid metals.

Californium-252, because 3 percent of its decay occurs by spontaneous fission, is industrially and medically important as a very intense source of neutrons. One microgram releases 170,000,000 neutrons per minute.