Symbol

Am

Atomic Number

95

Atomic Mass

243.0614

Family

Actinide Transuranium element

Pronunciation

am-uh-REE-see-um

Overview

Americium is called an actinide or transuranium element. It occurs in Row 7 of the periodic table, a chart that shows how the chemical elements are related to each other. The first element in that row is actinium, which explains the name actinide. The term transuranium means "beyond uranium" on the periodic table. Uranium has an atomic number of 92. Any element with an atomic number larger than 92, therefore, is called a transuranium element.

Discovery and Naming

Americium was discovered as a by-product of military research during World War I I (1939-45). The U.S. government maintained a major research site at the University of Chicago during the war. Work there led to the development of the first atomic bomb. During that research, a team from the University of California, consisting of Glenn Seaborg (1912- ), Albert Ghiorso...