Thorium

Atomic number

90

Atomic mass (u)

232.038

Category

Actinide

Standard state

Solid

Melting point

1749.85 °C (2023 K)

Boiling point

4787.85 °C (5061 K)

Density (g/cm³)

11.72

Electronegativity (Pauling)

1.3

Electron configuration

[Rn]7s2 6d2

Oxidation states

+4

Atomic radius (pm)

237

First ionization energy (eV)

6.08

Discovery & recognition

Discovery year / period (PubChem)

1828

Discovery credited to (RSC)

Jöns Jacob Berzelius

Date or period recorded by RSC

1829

Discovery place

Stockholm, Sweden; source specimen from near Brevig, Norway

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Thorium is found as the minerals thorite, uranothorite and thorianite.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.