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It's Elemental

The Element Actinium

[Click for Isotope Data]


89 Ac Actinium 227

Atomic Number: 89

Atomic Weight: 227

Melting Point: 1324 K (1051°C or 1924°F)

Boiling Point: 3471 K (3198°C or 5788°F)

Density: 10.07 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 7

Group Number: none

Group Name: Actinide

Special Notes: Radioactive

What's in a name? From the Greek word for a beam or ray, aktis.

Say what? Actinium is pronounced as ak-TIN-ee-em.

History and Uses:

Actinium was discovered in 1899 by André-Louis Debierne, a French chemist, while experimenting with new methods of separating rare earth oxides. Friedrich Otto Giesel independently discovered actinium in 1902.

Actinium is a rare element that is present in uranium ores in tiny amounts, but it is usually cheaper and easier to create actinium when it is needed by bombarding radium with neutrons in a nuclear reactor.

Actinium's most stable isotope, actinium-227, has a half-life of 21.77 years. It decays into francium-223 through alpha decay or into thorium-227 through beta decay.

Actinium has no significant commercial applications, although it is used in the production of neutrons.

Estimated Crustal Abundance: 5.5×10-10 milligrams per kilogram

Estimated Oceanic Abundance: Not Applicable

Number of Stable Isotopes: 0 (View all isotope data)

Ionization Energy: 5.17 eV

Oxidation States: +3

Electron Shell Configuration:


2s2   2p6

3s2   3p6   3d10

4s2   4p6   4d10   4f14

5s2   5p6   5d10

6s2   6p6   6d1


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For questions about this page, please contact Steve Gagnon.