89Ac Actinium

Year Discovered


Discovered By

Andre Debierne of France

Biological Rating

Not necessary for life.


Named from the Greek word meaning “ray”, actinium is a soft, silvery-white radioactive metal. It is the first metal of the actinide series, which includes the 15 elements from actinium to lawrencium. Like the lanthanides, The actinides, like lanthanides, are often referred to as “rare-earth elements” and also share several characteristics with the lanthanides. In general, actinides are very chemically active metals, and will react with air, water and acids, but not with bases. All actinides are radioactive and only thorium and uranium are commonly found in the Earth’s crust. Actinium itself glows in the dark and reacts with water to produce hydrogen gas. It also reacts with air and acids, but not bases. It is used in thermoelectric power sources and also used in neutron emitters. The most stable isotope of actinium has a half-life 21.8 years.

Biological Benefits

Actinium has no biological use.

Role in Life Processes

No known benefits for life processes for plants and animals.


Actinium is part of the decay series of uranium. As such it is found in very minute amounts in uranium-bearing rock. It is also produced in very small amounts in nuclear reactors.