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curium

The Columbia Encyclopedia, Sixth Edition | Date: 2008

curium , artificially produced radioactive chemical element; symbol Cm; at. no. 96; mass no. of most stable isotope 247; m.p. about 1,340°C; b.p. 3,110°C; sp. gr. 13.5 (calculated); valence +3, +4. A hard, brittle, silvery metal that tarnishes in air, curium is chemically reactive and resembles gadolinium in its chemical properties, although it has a more complex crystalline structure. Oxides, fluorides, a chloride, a bromide, and an iodide of curium have been prepared. Curium is a member of the actinide series in Group 3 of the periodic table . Sixteen isotopes of curium are known. Curium-242, prepared by neutron bombardment of americium-241, has a half-life of 163 days; curium-247, the most stable isotope, has a half-life of 15.6 million years. Some curium isotopes are available in multigram quantities.

Curium is intensely radioactive; it is about 3,000 times as radioactive as radium . It is also very toxic when absorbed into the body because it accumulates in the bones and disrupts the formation of red blood cells. Curium-242 and curium-244 are used in the space program as a heat source (from the heat they generate as they undergo radioactive decay) for compact thermionic and thermoelectric power generation.

Curium has not been found to occur naturally; it was the third transuranium element to be synthesized. Curium was first produced by the bombardment of plutonium-239 with alpha particles in a cyclotron at the Univ. of California at Berkeley. Identified in 1944 by Glenn T. Seaborg , Ralph A. James, and Albert Ghiorso, it was named for Pierre and Marie Curie , the noted pioneers in the study of radioactivity. The metal was first isolated in visible amounts as the hydroxide by L. B. Werner and I. Perlman in 1947.

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The Columbia Encyclopedia, Sixth Edition. Copyright 2008 Columbia University Press