Symbol

Pu

Atomic Number

94

Atomic Mass

244.0642

Family

Actinide Transuranium Elem Pronunciation

plu-TOE-nee-um

Overview

Plutonium is a synthetic (artificial) element. It exists naturally only in the smallest imaginable amounts. Plutonium was first prepared artificially by a team of researchers at the University of California at Berkeley (UCB) in 1941. News of this discovery was not released, however, until 1946. This delay was caused by the need for secrecy about scientific developments during World War I I (1939-45).

Plutonium is a member of the actinide family. The actinides occur in Row 7 of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. The actinides get their name from element 89, actinium, which is sometimes considered the first member of the family. Plutonium is also called a transuranium element. The term transuranium means "beyond uranium." Elements with atomic numbers greater than that of uranium (92) are...