Actinium Facts – Atomic Number 89 or Ac

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These are vials of glowing actinium-225. Oak Ridge National Laboratory, US Department of Energy
These are vials of glowing actinium-225. Oak Ridge National Laboratory, US Department of Energy

Element Name: Actinium

Symbol: Ac

Atomic Number: 89

Atomic Weight: 227.0278

Electron Configuration: [Rn] 6d1 7s2

Element Classification: Radioactive Rare Earth (Actinide Series)

Discovery: Andre-Louis Debierne 1899 (France)

Word Origin: Greek: akis, aktinos (ray).

Melting Point (K): 1320

Boiling Point (K): 3470

Appearance: heavy, silvery-white metal that is highly radioactive – glows with a pale blue light

Atomic Radius (pm): 188

Atomic Volume (cc/mol): 22.54

Ionic Radius: 118 (+3e)

Fusion Heat (kJ/mol): (10.5)

Evaporation Heat (kJ/mol): (292.9)

Pauling Negativity Number: 1.1

First Ionizing Energy (kJ/mol): 665.5

Oxidation States: 3

Lattice Structure: Face-Centered Cubic

Lattice Constant (Å): 5.310

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange’s Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)