Actinium

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

Actinium (Ac) is chemical element 89, an actinide in the f-block, period 7 (PubChem).

Atomic number: 89
Symbol: Ac
Group: none (f-block)
Period: 7
Atomic mass: 227.02775 u
Electron configuration: [Rn]7s2 6d1
Electronegativity (Pauling scale): 1.1
Atomic radius (van der Waals): 260 pm
Ionization energy: 5.17 eV
Oxidation states: +3
Standard state: Solid
Melting point: 1324 K
Boiling point: 3471 K
Density: 10.07 g/cm³
Chemical group: Actinide
Year discovered: 1899

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