91Pa Protactinium

Year Discovered


Discovered By

Kasimir Fajans and O. Gohring of Germany

Biological Rating

Not necessary for life.


Named from the Greek word meaning “the first”, protactinium is a silvery, radioactive metal. It is chemically active, reacting with air, water and acids but not bases. Protactinium is one of the rarest elements and is found in minute quantities in uranium minerals and ores, and can be extracted from these sources in gram quantities. Protactinium has few uses, but becomes superconducting at very low temperatures. The most stable isotope of protactinium has a half-life of 32,500 years.

Biological Benefits

Protactinium has no biological use. It is believed to stimulate the metabolism.

Role in Life Processes

No known benefits for life processes in plants and animals.


Protactinium is a decay product of uranium, and can be extracted in very small quantities from uranium minerals.