Scandium (Sc)

Scandium (symbol Sc) is the chemical element with atomic number 21: a transition metal, solid at 0 °C, with an atomic mass of 44.956 u. Discovered in 1879 (Lars Fredrik Nilson).

Scandium is a light metal whose existence and properties Mendeleev predicted before its discovery, under the name “eka-boron.” It is not especially rare in Earth's crust, but it is widely dispersed, which makes it hard and costly to produce. Added in small amounts to aluminium, it makes it markedly stronger.

Key facts

Atomic number: 21
Symbol: Sc
French name: Scandium
Atomic mass: 44.956 u
Molar mass: 44.956 g/mol
Family: Transition metals
Position: period 4, group 3, d-block
State at 0 °C: Solid
Melting point: 1,540.9 °C
Boiling point: 2,835.9 °C
Density: 2.99 g/cm³
Electronegativity (Pauling): 1.36
First ionization energy: 633 kJ/mol
Atomic radius: 160 pm
Electron configuration: [Ar] 3d¹ 4s²
Abundance in Earth's crust: 22 ppm (31st most abundant element)
Indicative price: 3,500 $/kg (order of magnitude)
Radioactive: no
Discovery: 1879, Lars Fredrik Nilson

Origin of the name

From Scandinavia.

What does scandium look like?

A relatively soft, silvery-white metal that takes on a faint yellowish or pinkish tint in air.

Where is scandium found?

About 22 ppm of Earth's crust, more than lead or tin, but it almost never forms concentrated deposits. It is recovered as a by-product of processing uranium, rare earths, titanium or nickel.

Natural sources

Thortveitite
Euxenite
Gadolinite
Nickel laterites

How is scandium produced?

It is extracted as a by-product from mining residues, then converted to scandium oxide. World production is only a few dozen tonnes of oxide a year, making it an expensive metal that is little used despite its qualities.

Top producers

China
Russia
Philippines

What is scandium used for?

Aluminium-scandium alloys for aerospace and sports gear.
Solid oxide fuel cells (scandium-stabilized zirconia).
Metal-halide lamps that produce light close to sunlight.
Lasers and specialty ceramics.

In everyday life

Some high-end bike frames
Alloy baseball bats
Floodlights in stadiums and TV studios

Role in living things

No known biological role. It is present in vanishingly small traces in the environment.

Hazards of scandium

Little studied, it is considered to have low toxicity. Metal dust is flammable, and some compounds can irritate the airways.

Cosmic origin

Supernovae: Forged in the cores of massive stars, then scattered when they explode.

History of scandium

In 1871, Mendeleev announced a missing element, “eka-boron,” with a mass of about 44. In 1879, the Swede Lars Fredrik Nilson discovered it in euxenite and gadolinite from Scandinavia and named it scandium. His compatriot Per Teodor Cleve immediately recognized it as Mendeleev's eka-boron, a triumph for the periodic table.

Did you know?

Parts of Soviet MiG-29 fighter jets used aluminium-scandium alloys.
Scandium is more abundant in the crust than gold, silver or lead, yet it can cost more than gold by the kilogram.
It is named after Scandinavia, where it was discovered.

Isotopes of scandium

A single stable isotope, scandium-45. Several radioactive isotopes hold promise in nuclear medicine for both seeing and treating tumors.

scandium-44: radioactive, half-life 4.04 h. Positron emitter being studied for PET imaging.
scandium-45: 100% of natural scandium, stable
scandium-46: radioactive, half-life 83.8 days. Tracer in the oil industry and for tracking sediments.
scandium-47: radioactive, half-life 3.35 days. Candidate for targeted cancer radiotherapy, teamed with scandium-44 for imaging.

Related elements

Same family (transition metals): Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), Cadmium (Cd), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au), Mercury (Hg), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs).

Same column (group 3): Yttrium (Y), Lanthanum (La), Actinium (Ac).