ELEMENTLE

Element 21 · Transition Metal

Scandium

Period 4 · Group 3

Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic d-block element, it has historically been sometimes classified as a rare earth element, together with yttrium and the lanthanoids. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia.

Three reasons Scandium stands out

  1. 1

    Used in aerospace and sporting goods.

  2. 2

    Its existence was predicted by Mendeleev before it was ever discovered, as a missing gap in his periodic table.

  3. 3

    Adding it to mercury-vapour lamps produces artificial light that closely mimics natural sunlight.

A scarce metal with a quiet supporting role

Scandium is dispersed so thinly through minerals that concentrated ores are unusual. Small additions can make aluminum alloys stronger and easier to weld, useful where low mass matters. Scandium iodide in metal-halide lamps also helps produce light resembling natural daylight.

Scandium at a glance
Atomic number / protons21
SymbolSc
Family (Elementle)Transition Metal
Classification (PubChem)Transition metal
Period4
Group3
Atomic mass (u)44.95591
Standard stateSolid
Electron configuration[Ar]4s2 3d1
Reported oxidation states+3
Electronegativity (Pauling)1.36
Atomic radius (pm)211
First ionization energy (eV)6.561
Electron affinity (eV)0.188
Density (g/cm³)2.99
Melting point1814 K (1,540.85 °C)
Boiling point3109 K (2,835.85 °C)
Discovery (PubChem)1879

Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.

Sources & further reading

PubChem: Scandium · Scandium on Wikipedia

The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.