CAS Number54038-81-2
PubChem CIDna
Atomic Radius-
Atomic Volume-
Atomic Weight[269]
Boiling Point-
Bulk Modulus
CategoryTransition metals
Crystal Structure
Covalent Radius143
Electrical Resistivity
Electron Configuration[Rn] 5f14 6d4 7s2
Electrons per shell2, 8, 18, 32, 32, 12, 2
Heat of Fusionna
Heat of Vaporizationna
Ionization Potential-
Magnetic Ordering
Magnetic Susceptibility
Mass Number106
Melting Point-
Atomic Number262
Oxidation States6
Poisson Ratio
Shear Modulus
Specific Heat Capacity-
Thermal Conductivity-
Van der Waals radius
Young's Modulus
Abundance in Earth's crustna
Abundance in Universena
Sg Seaborgium 106 (263) 6 7 d 106 [Rn] 5f14 6d4 7s2 2 8 18 32 32 12 2 None Unknown 1 1.94 h 2.78h AlphaEmission TransitionMetal, Metal, Radioactive, Synthetic see-BORG-i-em Synthetic radioactive metal. It has no significant commercial applications. Made by bombarding californium-249 with oxygen-18. itreFICfo3I Seaborgium
André-Louis Debierne, a French chemist, discovered actinium in 1899.

He separated it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium.

Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum. From the Greek aktis, aktinos, meaning beam or ray 106 1974 Albert Ghiorso and others The Lawrence Berkeley Laboratory in California and the Livermore National Laboratory, USA. Glenn T. "Seaborg", American nuclear chemist and Nobel prize winner.

Isotopes of Actinium

Standard Atomic Weight

Stable Isotopes

Unstable Isotopes

258Sg 259Sg 260Sg 261Sg 262Sg 263Sg 264Sg 265Sg 266Sg 267Sg 268Sg 269Sg 270Sg 271Sg 272Sg 273Sg

Actinium is highly radioactive
Actinium glows in the dark with a pale blue light
Actinium is used as an active element of radioisotope thermoelectric generators, for example in spacecraft.

The medium half-life of 227Ac makes it very convenient radioactive isotope in modeling the slow vertical mixing of oceanic waters.

225Ac is applied in medicine to produce 213Bi in a reusable generator or can be used alone as an agent for radiation therapy.