Symbol

Ba

Atomic Number

56

Atomic Mass

137.34

Family

Group 2 (Iia) Alkaline Earth Metal Pronunciation

BARE-ee-um

Overview

Barium was first isolated in 1808 by English chemist Sir Humphry Davy (1778-1829). In 1807 and 1808, Davy also discovered five other new elements: sodium, potassium, strontium, calcium, and magnesium. All of these elements had been recognized much earlier as new substances, but Davy was the first to prepare them in pure form. (See sidebar on Davy in the Calcium entry.)

Barium had first been identified as a new material in 1774 by Swedish chemist Carl Wilhelm Scheele (1742-86). The form with which Scheele worked, however, was a compound of barium, barium sulfate (BaSO₄). Barium sulfate is, in fact, the most common naturally occurring ore of barium. It is generally known as barite or barytes.

Barium is a member of the alkaline earth metals. The alkaline earth metals make up Group 2 (IIA) of the periodic table. The...