8392. Scandium

Nomenclature

CAS number: 7440-20-2

Description and references

Sc; at. wt 44.955912; at. no. 21; valence 3. Group IIIb (3). Rare earth metal. Naturally occurring isotope (mass number): 45; known artificial radioactive isotopes: 40-44, 46-51. Abundance in earth's crust: 5-25 ppm. Widely dispersed in nature. Occurs in the minerals thortveitite [(Sc,Y)2Si2O7] and in other rare earth minerals such as davidite, ytterbite, orthite and cerrite; frequently associated with tin or zirconium. Predicted and called “ekaboron” by Mendeleev. Discovered by Nilson: Ber. 12, 551, 554 (1879); 13, 1430, 1439 (1880). Sepn from wolframite: Lukens, J. Am. Chem. Soc. 35, 1470 (1913); on basis of solubility: Fischer, Bock, Z. Anorg. Chem. 249, 146 (1942). Toxicity of the chloride: Haley et al., J. Pharm. Sci. 51, 1043 (1962). Review of isolns including ion-exchange techniques: F. H. Spedding et al., J. Electrochem. Soc. 105, 683-686 (1958). Review of prepn, properties and compds: R. C. Vickery, The Chemistry of Yttrium and Scandium (Pergamon Press, New York, 1960) 123 pp; idem, “Scandium, Yttrium and Lanthanum” in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 329-353; T. Moeller, “The Lanthanides”, ibid. vol. 4, pp 1-101; F. H. Spedding in Kirk-Othmer Encyclopedia of Chemical Technology vol. 19 (John Wiley & Sons, New York, 3rd ed., 1982) pp 833-854; Chemistry of the Elements, N. N. Greenwood, A. Earnshaw, Eds. (Pergamon Press, New York, 1984) pp 1102-1110, 1423-1449.

Properties

Metal. Reported to be dimorphic. Crystalline forms: hexagonal close-packed α-form, d 2.9890; evidence of existence of face-centered cubic β-form, d 3.19, is inconclusive. mp 1541°. bp 2836°. Heat of fusion: 14.10 kJ/mol. Heat of sublimation (25°): 377.8 kJ/mol. E°(aq) Sc3+/Sc -2.08 V (calc). Salts are hydrolyzed in aq soln.

Derivative

Oxide.

Nomenclature

Scandia.
O3Sc2; mol wt 137.91.
O 34.80%, Sc 65.20%.

Properties

Fine white powder, d 3.864. Obtained by igniting the metal or its compds. Readily sol in hot or concd acids.

Derivative

Hydroxide.
Sc(OH)3; mol wt 95.98.
Sc 46.84%, O 50.01%, H 3.15%.

Properties

White gelatinous precipitate forming a hard, horny mass on exposure to air; obtained by the action of alkalies on solns of the salts; dissolves readily in dil acids.

Derivative

Chloride.
ScCl3; mol wt 151.31.
Sc 29.71%, Cl 70.29%.

Properties

White deliquescent solid. Prepd by the action of a mixture of sulfur chloride and chlorine on the heated oxide; mp 960°; crystallizes with 6 mols of water. Sol in water. Practically insol in alc. LD50 in mice: 755 mg/kg i.p.; 4 g/kg orally (Haley).

Derivative

Sulfate.
Sc2(SO4)3; mol wt 378.10.
Sc 23.78%, S 25.44%, O 50.78%.

Properties

Pentahydrate, d 2.519. Most sol of the sulfates of the rare earths (54.6 g/100 ml at 25°). Converted to the dihydrate on heating above 100°.

Derivative

Nitrate.
Sc(NO3)3; mol wt 230.97.
Sc 19.46%, N 18.19%, O 62.34%.

Properties

Crystallizes as the tetrahydrate, prismatic deliquescent crystals, readily dissolves in water or alc.