Actinium

Atomic number

89

Atomic mass (u)

227.02775

Category

Actinide

Standard state

Solid

Melting point

1050.85 °C (1324 K)

Boiling point

3197.85 °C (3471 K)

Density (g/cm³)

10.07

Electronegativity (Pauling)

1.1

Electron configuration

[Rn]7s2 6d1

Oxidation states

+3

Atomic radius (pm)

260

First ionization energy (eV)

5.17

Discovery & recognition

Discovery year / period (PubChem)

1899

Discovery credited to (RSC)

Andrew Debierne

Date or period recorded by RSC

1899

Discovery place

Paris, France

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.

“Actinium used for research purposes is made by the neutron bombardment of radium-226.”

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.