Structural Formula Vector Image
Title: Californium
CAS Registry Number: 7440-71-3
Literature References: Cf; at. no. 98; valence 4, 3, 2. Man-made, radioactive element. No stable nuclides; known isotopes (mass numbers): 239-256. Longest-lived known isotope: 251 (T½ 898 years, a-emitter, rel. at. mass 251.0796). Prepn of isotope 245Cf (T½ 43.6 min) by bombarding 242Cm with helium ions: S. G. Thompson et al., Phys. Rev. 78, 298 (1950); eidem, ibid. 80, 790. Prepn of 249Cf metal (T½ 351 years, a-emitter, rel. at. mass 249.0748) by reduction of Cf2O3 with lanthanum metal: Haire, Baybarz, J. Inorg. Nucl. Chem. 36, 1295 (1974). Medical uses of 252Cf (a-decay, T½ half-life 2.645 years, rel. at. mass 252.0816; spontaneous fission T½ half-life 85.5 years): Seaborg, Handb. Exp. Pharmakol. 36, 929 (1973). Reviews: Cunningham, J. Chem. Educ. 36, 32-37 (1959); M. Haissinsky, J. P. Adloff, Radiochemical Survey of the Elements (Elsevier, New York, 1965) pp 28-29; C. Keller, The Chemistry of the Transuranium Elements (Verlag Chemie, Weinheim, English Ed., 1971) pp 567-581; Silva, "Trans-Curium Elements" in MTP Int. Rev. Sci.: Inorg. Chem., Ser. One vol. 8, A. G. Maddock, Ed. (University Park Press, Baltimore, 1972) pp 71-105; Comprehensive Inorganic Chemistry vol.5, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) passim; Handb. Exp. Pharmakol. 36, 689-928 (1973); R. G. Haire in The Chemistry of the Actinide Elements vol. 2, J. J. Katz et al., Eds. (Chapman and Hall, New York, 1986) pp 1025-1070. Review of radiobiology and therapeutic applications: Y. Maruyama et al., Oncology 35, 172 (1978); of use in brachytherapy for cervical cancer: idem et al., Cancer 68, 1189-1197 (1991). Review of production, distribution and uses of 252Cf: R. C. Martin et al., Appl. Radiat. Isot. 53, 785-792 (2000).
Properties: Metal; two crystalline forms: double hexagonal close-packed a-form, d 15.10, exists below 900°; face-centered cubic b-form, d 8.74 (Katz et al., loc. cit. vol. 2, p. 1150). mp 900±30° (Haire, Baybarz). Slowly oxidized in air at room temp; rate increases with increased moisture in air. Oxidized when warmed in air; reacts when heated with nitrogen, hydrogen or a chalogen. Reacts rapidly with dry hydrogen halides and with aq mineral acids.
Melting point: mp 900±30° (Haire, Baybarz)
Density: d 15.10; d 8.74 (Katz et al., loc. cit. vol. 2, p. 1150)
CAUTION: Radiation hazard; handling requires special equipment and shielding facilities (Katz et al., loc. cit. vol. 2, p. 1128).
Use: 252Cf as neutron source; startup source for nuclear reactors; in nuclear reactor fuel rod scanners; for neutron radiography of weapons components.
Therap-Cat: 252Cf as antineoplastic (radiation source).

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