Scandium – facts and properties

Position in the periodic table

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Occurrence and extraction

Scandium is roughly as common in the Earth's crust as cobalt and more common than lead. It still counts as a rare metal because it is thinly spread and seldom concentrated in deposits of its own. Its only important mineral, thortveitite, occurs in Norway and Madagascar, and only in small amounts. Almost all scandium today is a by-product, recovered while processing ores of titanium, uranium, nickel or the rare earths. World output is only a few dozen tonnes of scandium oxide a year.

The Swedish chemist Lars Fredrik Nilson discovered scandium in 1879 in the Scandinavian minerals euxenite and gadolinite, and named it after Scandinavia. Shortly afterwards his compatriot Per Teodor Cleve realised that this was the element Mendeleev had called eka-boron a few years earlier. Mendeleev had worked out its atomic mass and the formula and density of its oxide from a gap in his table. The discoveries of scandium, gallium and germanium did a great deal to win acceptance for his periodic system. Pure scandium metal was only produced in the twentieth century, by electrolysis of a molten salt mixture.

Properties and reactions

Scandium sits in period 4 and group 3, with the electron configuration [Ar] 3d¹ 4s². That means it has just one d electron. When the atom gives up its two 4s electrons and its single 3d electron, it forms the Sc³⁺ ion, which has the same electron arrangement as argon. In compounds, scandium therefore almost always has an oxidation state of plus three. Because this ion has no d electrons left, scandium compounds are usually colourless, unlike the brightly coloured compounds of many other transition metals. In its chemistry scandium resembles yttrium and the lanthanoids, and it is grouped with them as one of the rare earth metals.

With a density of 2.99 g/cm³, scandium is only slightly heavier than aluminium. It melts at 1541 °C and boils at 2836 °C, and its electronegativity is 1.36. In air the metal forms a thin oxide film and takes on a faint yellowish tint. It dissolves in dilute acids, giving off hydrogen. Heated in air it burns to scandium oxide, Sc₂O₃, a white powder with a very high melting point.

Uses in everyday life and technology

The main application is aluminium–scandium alloys. Adding just a few tenths of a percent of scandium refines the grain structure of aluminium, raises its strength considerably and makes it easier to weld. Such alloys are used in aerospace and in sports equipment such as bicycle frames and baseball bats, and some lightweight revolvers have scandium alloy frames. Because scandium is expensive, it remains limited to specialist uses for now.

Scandium iodide is one of the salts inside metal halide lamps. These lamps give a very bright light close to daylight and are used to light sports stadiums and film sets. Another field is solid oxide fuel cells: zirconium dioxide doped with scandium oxide conducts oxide ions particularly well at high temperatures and serves as the electrolyte.

Scandium has no known role in living things. At the low levels found in the environment it is not considered a hazard.

Quick question

Which element has the electron configuration [Ar] 4s1?

FAQ