Scandium

Scandium (Sc) is a transition metal with atomic number 21 and an atomic mass of 44.956. Its electron configuration is [Ar] 3d1 4s2.

Scandium key data

Symbol	Sc
Atomic number	21
Atomic mass (standard atomic weight)	44.956
Molar mass	44.956 g/mol
Protons	21
Neutrons (most abundant isotope, scandium-45)	24
Electrons (neutral atom)	21
Category	Transition metal
Period	4
Group	3
Block	d-block
Noble gas notation	[Ar] 3d1 4s2
Full electron configuration	1s2 2s2 2p6 3s2 3p6 3d1 4s2
Electrons per shell	2, 8, 9, 2

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

Measured properties of scandium

From PubChem, the US National Institutes of Health. Public domain.

Melting point	1814 K (1540.9 °C), 25th of 103 by melting point
Boiling point	3109 K (2835.9 °C), 40th of 93 by boiling point
Density	2.99 g/cm³, 70th of 96 by density
State at room temperature	Solid
Electronegativity	1.36 (Pauling), joint 57th of 95 by electronegativity
Van der Waals radius	211 pm, joint 44th of 99 by atomic radius
First ionisation energy	6.561 eV (633 kJ/mol), 60th of 102 by first ionisation energy
Electron affinity	0.188 eV (18.1 kJ/mol), 54th of 57 by electron affinity
Common oxidation states	+3
Discovered	1879

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Scandium electron configuration

The full electron configuration of scandium is 1s2 2s2 2p6 3s2 3p6 3d1 4s2. With the noble-gas core collapsed it is [Ar] 3d1 4s2, and the outermost subshell is 4s2.

Bohr model of scandium (Sc): a nucleus and four shells holding 2, 8, 9 and 2 electrons from the inside out. — Bohr model of scandium (Sc). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Orbital box diagram of scandium (Sc), 1s2 2s2 2p6 3s2 3p6 3d1 4s2: one box per orbital, filled by Hund’s rule, showing one unpaired electron, in 3d. — Orbital diagram of scandium (Sc). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one scandium atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

one atom = 44.956 / (6.02214076 × 10²³)
= 7.4651 × 10⁻²³ g

Atoms in one gram

atoms per gram = 6.02214076 × 10²³ / 44.956
= 1.3396 × 10²² atoms

Scandium on the periodic table

Scandium is in period 4, group 3, in the d-block.

Group 3 is scandium, yttrium and then either lanthanum and actinium or lutetium and lawrencium, depending on which convention a table follows.