0 a chemical element that is a soft, silver-white metal and is radioactive:
Researchers are testing the actinium.
Thorium decays into a radium isotope, and then into actinium, which has a 10-day half-life.
Various alternative processes have been proposed for making actinium.
Secondary decay products of thorium include radium and actinium.
Owing to its scarcity, high price and radioactivity, actinium has no significant industrial use.
The actinide series derives its name from the group 3 element actinium.
The new name meant parent of actinium and reflected the fact that actinium is a product of radioactive decay of protactinium.
The former reaction is carried out at room temperature, by adding hydrofluoric acid to a solution containing actinium ions.
