Thorium

Document v1 · published by Koskamo · updated 2026-10-04

Thorium (Th) is chemical element 90, an actinide in the f-block, period 7 (PubChem).

Atomic number: 90
Symbol: Th
Group: none (f-block)
Period: 7
Atomic mass: 232.038 u
Electron configuration: [Rn]7s2 6d2
Electronegativity (Pauling scale): 1.3
Atomic radius (van der Waals): 237 pm
Ionization energy: 6.08 eV
Oxidation states: +4
Standard state: Solid
Melting point: 2023 K
Boiling point: 5061 K
Density: 11.72 g/cm³
Chemical group: Actinide
Year discovered: 1828

Source and provenance

Original source: pubchem.ncbi.nlm.nih.gov
Published on Koskamo by: Koskamo
Citation version: Document v1
Reuse: PubChem periodic table data (NIH/NLM, pubchem.ncbi.nlm.nih.gov/ptable); group and period from Jefferson Lab via PubChem

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Version history

Published by Koskamo2026-10-04
Version 1