Symbol

Se

Atomic Number

34

Atomic Mass

78.96

Family

Group 16 (Via) Chalcogen Pronunciation

suh-LEE-nee-um

Overview

Selenium is a member of the chalcogen family. The chalcogens are elements in Group 16 (VIA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Other chalcogens are oxygen, sulfur, tellurium, and polonium. The name chalcogen comes from the Greek word chalkos, meaning "ore." The first two members of the family, oxygen and sulfur, are found in most ores.

Selenium is a metalloid. A metalloid is an element that has some characteristics of a metal and some of a non-metal.

Selenium and tellurium are often associated with each other. They tend to occur together in the Earth and have somewhat similar properties. They have many uses in common. In recent years, some important new uses have been found for selenium. It is now used in...