Discovered | Characteristics | Prepared | Uses

Actinium is a metal in Group IIIB and the 7th period. Other members of the group are scandium (Sc), yttrium (Y), and lanthanum (La). It is the first element in the series known as the actinides.

It was discovered in 1899 by Debierne in uranium-bearing ores. It arises from decay of uranium--235, but it can be synthesized by neutron bombardment of radium.

The met al is prepared by reduction of AcF3 with lithium vapor at 1100-1300°C. The metal resembles La chemically.

Actinium--227 is beta-emitter with a half-life of 21.6 years. Its principal decay products are thorium--227 (half-life = 18.5 days) and radium--223 (half-life = 11.4 days). The energy involved in radioactive decay makes the element useful in thermo-electric power sources for satellites.