- Scandium (Sc) is a soft, silvery-white transition metal with atomic number 21, positioned in Group 3 of the periodic table.
- It has three valence electrons in its outermost shell (two in the 4s subshell and one in the 3d subshell), which it typically loses to form Sc³⁺ cations. Its atomic structure consists of twenty-one protons, usually twenty-four neutrons, and twenty-one electrons arranged in four shells.
- Naturally occurring scandium is monoisotopic, consisting entirely of the stable isotope scandium-45 (⁴⁵Sc). Several radioactive isotopes have been synthesized, including scandium-46, scandium-47, and scandium-48, which are used in research and certain industrial applications.
- Scandium is relatively rare in Earth’s crust, with an average abundance of about 22 parts per million, comparable to that of cobalt. It is dispersed in trace amounts in over 800 minerals but concentrated enough for commercial extraction mainly in minerals such as thortveitite [(Sc,Y)₂Si₂O₇], certain uranium ores, and as a by-product of rare earth element processing. Significant sources include deposits in Scandinavia (where it was first discovered), China, Madagascar, and parts of Russia.
- The element was discovered in 1879 by Swedish chemist Lars Fredrik Nilson, who identified it while analyzing the rare earth mineral euxenite. Nilson named it “scandium” after Scandia, the Latin name for Scandinavia. Its discovery confirmed the prediction of Dmitri Mendeleev, who had foreseen an “ekaboron” in the periodic table with properties similar to scandium. Metallic scandium was first produced in 1937 by electrolysis of molten scandium chloride (ScCl₃).
- Scandium’s primary uses are in specialized alloys and high-performance materials. When added in small amounts (0.1–0.5%) to aluminum, scandium significantly increases the strength, weldability, and corrosion resistance of the alloy, making it valuable in aerospace, marine, and sports equipment applications. These aluminum–scandium alloys are used in aircraft components, bicycle frames, baseball bats, and high-end firearms.
- In the field of lighting, scandium iodide (ScI₃) is used in metal halide lamps to produce light with a color spectrum similar to natural sunlight, useful in stadiums, television studios, and photography. Scandium isotopes, particularly scandium-46, are used as radioactive tracers in oil refining and in research related to corrosion and wear analysis.
- Chemically, scandium exhibits characteristics of both transition metals and rare earth elements. It forms mostly ionic compounds in the +3 oxidation state, such as scandium oxide (Sc₂O₃) and scandium chloride (ScCl₃). It has an affinity for oxygen, sulfur, and halogens, and forms stable complexes with many ligands. Scandium is resistant to corrosion in air due to the formation of a passivating oxide layer, though it slowly dissolves in acids.
- Biologically, scandium has no known essential role in living organisms and is considered non-toxic in small amounts. However, its compounds should be handled with care, as inhalation of fine powders may cause respiratory irritation. Environmentally, scandium’s scarcity and relatively low production rates (measured in tens of tonnes per year globally) limit its overall impact.
