Scandium (Sc)

Mendeleev predicted scandium in 1871, called it eka-boron, and specified its atomic weight and oxide formula from the gap in his table; Nilson found it eight years later and the numbers matched. It is not actually rare — there is more scandium in the crust than lead — but it is almost never concentrated anywhere, so it is produced in tonnes per year rather than thousands of tonnes, mostly as a by-product of uranium and titanium refining. Adding a fraction of a percent to aluminium roughly doubles the strength of the weld zone, which is why it turns up in frames that have to be welded and still be light.

Properties

Atomic number

21

Symbol

Sc

Standard atomic weight

44.956 u

Category

Transition metal

Group

3

Period

4

Block

d-block

Electron configuration

[Ar] 4s² 3d¹

Electrons per shell

2, 8, 9, 2

Melting point

1,814 K — 1540.8 °C — 2805.5 °F

Boiling point

3,109 K — 2835.8 °C — 5136.5 °F

Density

2.99 g/cm³

Electronegativity

1.36 (Pauling)

Oxidation states

+3

Discovered

1879 by Lars Fredrik Nilson

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹

Noble gas shorthand

[Ar] 4s² 3d¹

Shells

K: 2 · L: 8 · M: 9 · N: 2

What it is used for

• Scandium-aluminium alloy in high-end bicycle frames and baseball bats
• Airframe components on the Russian MiG-21 and MiG-29
• Scandium iodide in metal-halide lamps for stadium lighting
• Solid oxide fuel cell electrolytes

Neighbours in the table

Group 3

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Scandium sits in group 3 with yttrium.