Transition metalElement 21 · d-block

Scandium (Sc)

Scandium (Sc) is a transition metal with atomic number 21 and a standard atomic weight of 44.956. At room temperature it is a solid that melts at 1,541 °C and boils at 2,836 °C.

21ScScandium44.956

Atomic number

protons

Atomic weight

44.956

CIAAW 2024

Melting point

1,541 °C

1,814.15 K

Boiling point

2,836 °C

3,109.15 K

Density

2.99 g/cm³

near room temperature

Electronegativity

1.36

Pauling scale

State at 25 °C

Solid

Discovered

1879

Sweden

Scandium at a glance

Identity

Symbol	Sc
Atomic number (Z)	21
Atomic weight	44.956 ± 0.001 (CIAAW 2024)
Category	Transition metal
Group	3
Period	4
Block	d-block
CAS number	7440-20-2

Atomic properties

Electron configuration	[Ar] 3d¹ 4s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²
Electrons per shell	2, 8, 9, 2
Oxidation states	+3 Less common: 0, +1, +2
Electronegativity (Pauling)	1.36
First ionisation energy	6.561 eV (633.1 kJ/mol) 2nd: 12.8 eV · 3rd: 24.757 eV
Electron affinity	0.188 eV
Atomic radius (empirical)	160 pm
Covalent radius	148 pm
Van der Waals radius	215 pm

Physical properties

State at 25 °C	Solid
Melting point	1,541 °C · 2,805.8 °F · 1,814.15 K
Boiling point	2,836 °C · 5,136.8 °F · 3,109.15 K
Density	2.99 g/cm³
Specific heat capacity	0.568 J/(g·K)
Thermal conductivity	15.8 W/(m·K)
Crystal structure	Hexagonal

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	⁴⁵Sc 100%
Stable isotopes	6
Known isotopes	29
Abundance in Earth's crust	22 mg/kg
Abundance in seawater	0.0000006 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Scandium electron configuration

Scandium has 21 electrons. Written in short form, its ground-state configuration is [Ar] 3d¹ 4s² — the electrons of the noble gas argon, plus 3d¹ 4s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s².

3d↑

4s↑↓

Discovery and name

Discovered

1879 — Lars Fredrik Nilson · Sweden.

Name

Latin Scandia, Scandinavia.

Known for

A light rare-earth metal; small additions make strong aluminium–scandium alloys for bikes and aircraft. Scandium iodide is used in high-intensity lamps.

Isotopes of scandium

Naturally occurring scandium is a mix of 1 isotope. Each has 21 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
⁴⁵Sc	21	24	100%	stable

29 isotopes of scandium are known in our data set (half-lives as published in nuclear data tables).

Scandium compared with group 3

The other elements in group 3, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Scandium	21	44.956	1,541 °C	2,836 °C	2.99 g/cm³	1.36
Yttrium	39	88.906	1,522 °C	3,345 °C	4.47 g/cm³	1.22

Frequently asked questions

6 answers

What is the atomic mass of scandium?

The standard atomic weight of scandium is 44.956 ± 0.001 (CIAAW 2024), so one mole weighs about 44.956 grams.

How many protons, neutrons and electrons does scandium have?

A neutral scandium atom has 21 protons and 21 electrons. Its most common isotope, scandium-45, has 24 neutrons.

What is the electron configuration of scandium?

[Ar] 3d¹ 4s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²).

What are the melting and boiling points of scandium?

Scandium melts at 1,541 °C (2,805.8 °F) and boils at 2,836 °C (5,136.8 °F).

Is scandium a metal?

Scandium is a metal. It is in group 3, period 4, and is a solid at room temperature.

Who discovered scandium?

1879 — Lars Fredrik Nilson (Sweden).