Scandium
MELTING POINT:
1,539°C
BOILING POINT:
2,832°C
DENSITY:
2.989 g/cm
3
MOST COMMON IONS:
Sc
3+
Drawing on his periodic law and his categorization of the elements, Russian chemist Dimitri Mendeleev predicted the existence of element 21 in 1871. However, it was not until 1879 that Swedish chemist Lars Frederick Nilson identified the element scandium as part of a novel compound he had isolated. Working with 10 kilograms (22 pounds) of euxenite, a mineral found only in Scandinavia at that time, Nilson eventually succeeded in purifying 2 grams (0.07 ounces) of what later became known as scandium oxide.
Since its discovery, scandium has been found only in several rare minerals. It is found in highest concentration in the Norwegian mineral thortveitite (35–40% scandium). Its abundance in Earth's crust is a point of conjecture; it is generally agreed that scandium occurs in greater abundance in the Sun and certain stars.
In addition to forming an oxide (scandium oxide, Sc 2 O 3 ), scandium is capable of forming a number of colorless salts. For instance, scandium reacts with halogens to form halides that have the formula ScX 3 (where X = F, Cl, Br, or I). Additionally it occurs as an aqua ion, [Sc(H 2 O) 6 ] 3+ , which undergoes hydrolysis to form hydroxide-bridged metal clusters. A wide range of organic compounds may also react with scandium.
Because of its scarce distribution and difficulties associated with its extraction, scandium is very expensive. As a result and despite more than 100 years of research, it still has only a limited number of applications. It is added to aluminum alloys to increase the strength, thermal resistance, and durability of the materials (without adding much weight). Such alloys have been used to make everything from missiles to premium bicycle frames. Scandium is as light as aluminum but has a much higher melting point, thus its appeal to space missile designers.
SEE ALSO Aluminum ; Halogens ; Hydrolysis .
Helen R. Webb
Bibliography
Kilbourn, Barry T. (1993–1994). A Lanthanide Lanthology: A Collection of Notes Concerning the Lanthanides and Related Elements. White Plains, NY: Molycorp.