Californium

MELTING POINT: 900°C
BOILING POINT: Unknown
DENSITY: Unknown
MOST COMMON IONS: Cf²⁺, Cf³⁺

Element 98, named after the state of California, was first synthesized by the research group of Glenn Seaborg in 1950 at the University of California at

Berkeley. A target of microgram amounts of an isotope of curium (²⁴²Cm) was bombarded with accelerated helium ions in a cyclotron, to produce approximately 5,000 atoms of a californium isotope of mass 245 and a half-life of 44 minutes.

Californium, like all the actinide elements heavier than plutonium, exists in a stable trivalent oxidation state in aqueous solutions. It has also been found to exist in the (less stable) tetravalent oxidation state in solution. The ground state electronic configuration for the atom is 5f¹⁰7s². Metallic californium has a face-centered cubic structure near its melting point and a double hexagonal close-packed structure at temperatures below its melting point. Californium has eighteen isotopes, all of which are radioactive. The longest-lived isotope has a mass number of 251 and a half-life of 900 years. The isotope having mass number 252 and a half-life of 2.65 years undergoes radioactive decay, a fraction of which (3%) is via spontaneous nuclear fission; it releases neutrons in the fission event. Californium-252 has been used as a neutron source in a variety of analytical techniques, in medical diagnostic tests that require activation analysis, and in the production of short-lived nuclides. Californium neutron sources are used to image low density materials (especially hydrogenous materials). The compactness and portability of ²⁵²Cf neutron sources has resulted in their use in such areas as the detection of metals in deep wells, lunar exploration, and nuclear weapons monitoring.

Californium

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