Symbol

Es

Atomic Number

99

Atomic Mass

252.0828

Family

Actinide Transuranium Element Pronunciation

ein-STY-nee-um

Overview

Einsteinium is a member of the actinide family. The actinide elements are found in Row 7 of the periodic table, a chart that shows how chemical elements are related to each other. The actinides fall between radium (element number 88) and rutherfordium (element number 104). They are usually listed in a separate row at the very bottom of the periodic table.

Einsteinium is also a transuranium element. Transuranium elements are those beyond uranium on the periodic table. Uranium has an atomic number of 92, so elements with larger atomic numbers are transuranium elements

Discovery and Naming

Einsteinium was discovered by a research team from the University of California at Berkeley. The team was led by Albert Ghiorso (1915- ). The element was discovered in the "ashes" after the first hydrogen bomb test in November 1952 at Eniwetok Atoll, Marshall Islands, in...