The Element Actinium
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
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10
6s2 6p6 6d1
Citation and linking information
For questions about this page, please contact Steve Gagnon.