Periodic TableAll elementsThorium
No. 090
Th
232.04 u
Element · Actinide

Thorium

Thorium (钍, symbol Th) is chemical element number 90, an Actinide in period 7 of the periodic table, with a standard atomic weight of about 232.04. Weakly radioactive actinide. Considered a potential nuclear fuel.

Period 7Group —[Rn] 6d² 7s²

Properties

Atomic number90
SymbolTh
Atomic mass232.04 u
CategoryActinide
Period7
Group
Electron configuration[Rn] 6d² 7s²
Electronegativity1.3
Covalent radius206 pm
Density11.72 g/cm³
Melting point2115 K
Boiling point5061 K
DiscoveryJöns Jakob Berzelius, 1828

Overview

Weakly radioactive actinide. Considered a potential nuclear fuel. Thorium (Th) is an Actinide with atomic number 90, located in period 7. As an actinide it is typically radioactive and closely tied to nuclear technology.

It has the configuration [Rn] 6d² 7s² and an electronegativity near 1.3; its 2 outer-shell electrons drive its bonding. Under standard conditions it exists as a solid (a very high melting point); it melts near 2115 K (1841.9 °C), boils near 5061 K (4787.9 °C), has a density around 11.72 g/cm³.

It is widely used in Nuclear and Research. It is regarded as a high-hazard element, so handle it with appropriate care. It was first described by Jöns Jakob Berzelius in 1828. Browse elements of the same category in the browse view.

Electron shells

Th90

Electrons per shell: 2 · 8 · 18 · 32 · 18 · 10 · 2

Main uses

Hazard

HighRadioactive

Compounds containing Thorium

No compounds in this knowledge base contain Thorium yet.

Data sources

Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.