Scandium
Element 21 · Transition Metal
Scandium is a silvery-white transition metal that begins the d-block in period 4. Mendeleev predicted its existence as eka-boron before its discovery in 1879, and its properties matched his forecast closely. It has a single stable oxidation state, +3, and its chemistry resembles aluminium and the rare earths more than the later transition metals.
Scandium's claim to fame is metallurgical: tiny additions of scandium to aluminium create alloys that are far stronger and more weldable, prized in aerospace parts and premium sports equipment. Its rarity keeps it expensive, so it is reserved for applications where performance justifies the cost.
Key facts
| Atomic number | 21 |
|---|---|
| Atomic weight | 44.956 |
| Category | Transition Metal |
| Group / Period | 3 / 4 |
| Block | d |
| Electron configuration | [Ar] 3d1 4s2 |
| Common oxidation states | +3 |
| State at STP | Solid |
| Electronegativity | 1.36 |
| Atomic radius | 184 pm |
| Density | 2.985 g/cm³ |
| Melting point | 1541 °C |
| Boiling point | 2836 °C |
Occurrence
Scandium is widely dispersed but rarely concentrated, making it scarce despite being more abundant in the crust than lead. It occurs in minerals such as thortveitite and as a trace in wolframite and tin ores. Most commercial scandium is recovered as a byproduct of uranium, titanium, and rare-earth processing.
Applications
Aluminium-scandium alloys make stronger, lighter baseball bats and bicycle frames
Aerospace components use scandium alloys for high strength at low weight
Metal-halide stadium lamps contain scandium iodide for bright white light
Solid-oxide fuel cells use scandia-stabilized zirconia electrolytes
3D-printed aerospace parts increasingly rely on scandium-alloyed aluminium powder
Common compounds
- scandium oxide
- scandium fluoride
- scandium chloride
- scandium nitrate
The first kilogram of pure scandium metal was not produced until 1960.
Data source: IUPAC standard atomic weights 2021