Scandium Sc

Discovery

When Dmitri Mendeleev published his periodic table in 1869–1871, he left gaps for elements that should exist but had not yet been discovered. One of them, below boron, he called eka-boron and predicted its atomic weight of about 44 and the properties of its oxide.

In 1879 the Swedish chemist Lars Fredrik Nilson was analysing the rare minerals euxenite and gadolinite from Scandinavia, hoping to isolate rare earth elements. He found a new oxide with a distinctive spectrum and named its element scandium. Soon afterwards his colleague Per Teodor Cleve showed that scandium matched Mendeleev's eka-boron remarkably well, one of the first great confirmations of the periodic law.

Metallic scandium was not prepared until 1937, when German chemists electrolysed a molten mixture of potassium, lithium and scandium chlorides. Only in the 1970s did scandium alloys attract practical interest.

Origin of the name

Nilson named the element after Scandia, the Latin name for Scandinavia, where the minerals came from. The symbol is Sc. Scandium is often grouped with the rare earth elements, because it occurs in the same minerals and behaves similarly.

Main uses

• Aluminium alloys: adding a fraction of a percent of scandium refines the grain of aluminium and makes it stronger and more weldable. Such alloys have been used in some Soviet-era military aircraft parts and in high-end bicycle frames, baseball bats and firearm frames.
• Lighting: scandium iodide is added to metal-halide lamps to give bright light close to natural daylight, used in stadiums and film production.
• Fuel cells: scandium-stabilised zirconia is a highly conductive electrolyte for solid oxide fuel cells.
• Research: scandium compounds are used in lasers and as catalysts in organic synthesis.

Isotopes

Scandium has only one stable isotope, scandium-45. The radioactive scandium-46, with a half-life of about 84 days, has been used as a tracer in oil refineries to follow the movement of materials. In nuclear medicine, scandium-44 (a positron emitter with a half-life of about 4 hours) and scandium-47 (a beta emitter with a half-life of about 3.3 days) are being studied as a matched pair for imaging and treating tumours with the same chemistry.

In everyday life

Scandium has no known biological role and is not a concern in everyday life. Its main contact with the public is indirect, through the bright white lights of sports venues and occasional premium sporting goods.

World production is small, on the order of tens of tonnes of oxide per year, mostly as a by-product of processing other ores such as uranium, titanium and rare earths, which keeps its price high.