Yes. Thorium is a metal, classified as an actinide on the periodic table.

How many protons does thorium have?

Thorium has 90 protons. Its atomic number is 90, which is also the number of electrons in a neutral atom of thorium.

What group and period is thorium in?

Thorium is in period 7 of the periodic table. As an actinide in the f-block, it sits in a separate row below the main table and has no standard group number.

What is the atomic mass of thorium?

The atomic mass of thorium is 232.04 u (unified atomic mass units).

Element 90

Thorium (Th)

Actinide · Period 7 · f-block

Thorium (Th) is element 90 of the periodic table, an actinide in period 7 (f-block) with an atomic mass of 232.04 and is a solid at standard conditions.

At a glance

Atomic number: 90
Symbol: Th
Atomic mass: 232.04 u
Category: Actinides
Period: 7
Block: f-block
Phase at STP: solid

Electron structure

Electron configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d2 7s2
Shorthand configuration: [Rn] 6d2 7s2
Electrons per shell: 2, 8, 18, 32, 18, 10, 2
Oxidation states: +1, +2, +3, +4

Physical properties

Melting point: 2,115 K (1,841.85 °C)
Boiling point: 5,061 K (4,787.85 °C)
Density: 11.72 g/cm³
Phase: solid

Atomic properties

Electronegativity (Pauling): 1.3
Atomic radius: 180 pm
Covalent radius: 206 pm
First ionization energy: 587 kJ/mol
Electron affinity: 113 kJ/mol

Notable isotopes

Notable isotopes of Thorium: mass number, atomic mass, natural abundance, and stability.
Isotope	Mass	Abundance	Stability
Th-232	232.03806	-	Half-life 14 billion years

Common uses

Nuclear fuel research
Gas mantles
Welding electrodes
Optics

Discovery

Year: 1829
Discovered by: Jöns Jacob Berzelius
Country: Sweden

Frequently asked questions

Is thorium a metal?: Yes. Thorium is a metal, classified as an actinide on the periodic table.
How many protons does thorium have?: Thorium has 90 protons. Its atomic number is 90, which is also the number of electrons in a neutral atom of thorium.
What group and period is thorium in?: Thorium is in period 7 of the periodic table. As an actinide in the f-block, it sits in a separate row below the main table and has no standard group number.
What is the atomic mass of thorium?: The atomic mass of thorium is 232.04 u (unified atomic mass units).

Keep exploring

Thorium's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.