Structural Formula Vector Image
Title: Curium
CAS Registry Number: 7440-51-9
Literature References: Cm; at. no. 96; valence 3, 4. Man-made radioactive element. No stable nuclides; known isotopes (mass numbers): 238-251. Longest-lived known isotope: 247 (T½ 1.56 ´ 107 years, rel. at. mass 247.0703, a-decay). Prepn of first isotope, 242Cm (T½ 162.9 days, a-decay), in 1944 by G. T. Seaborg et al. in The Transuranium Elements, G. T. Seaborg et al., Eds. (McGraw-Hill, New York, 1949) pp 1554-1571. Prepn of metal: J. C. Wolfmann et al., J. Am. Chem. Soc. 73, 493 (1951). Properties: Cunningham, Wallman, J. Inorg. Nucl. Chem. 26, 271 (1964); Smith et al., J. Chem. Phys. 50, 5066 (1969). Reviews: M. Haissinsky, J.-P. Adloff, Radiochemical Survey of the Elements (Elsevier, New York, 1965) pp 41-43; C. Keller, The Chemistry of the Transuranium Elements (Verlag Chemie, Weinheim, English Ed., 1971) pp 529-551; Comprehensive Inorganic Chemistry vol 5, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) passim; Handb. Exp. Pharmakol. 36, 689-928 (1973); P. G. Eller, R. A. Penneman in The Chemistry of the Actinide Elements vol. 2, J. J. Katz et al., Eds. (Chapman and Hall, New York, 1986) pp 962-988.
Properties: Silvery, lusterous, malleable metal. Two allotropic modifications: double hexagonal close-packed a-form, d 13.51, transforms to b-form at ~1277°; face-centered cubic b-form, d 12.9, exists from ~1277° to mp. mp 1345°. bp (calc) 3110°. Metal dissolves rapidly in dilute acid solns; oxidizes rapidly in the presence of traces of oxygen. Pyrophoric when finely divided. Chemistry of trivalent state similar to that of trivalent lanthanides.
Melting point: mp 1345°
Boiling point: bp (calc) 3110°
Density: d 13.51; d 12.9
CAUTION: Radiation hazard; handling requires special equipment and shielding facilities (Katz et al., loc. cit. vol. 2, p 1128).
Use: 242Cm and 244Cm as power sources in radionuclide batteries for space and medical applications. 242Cm as radioactive heat source. 248Cm in accelerator studies to form superheavy elements.

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