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Chemistry of Barium

Barium takes it name from the Greek word barys for heavy. Barium was first discovered in 1774 by Carl Scheele, but was not isolated as a pure metal until 1808 when Sir Humphry Davy electrolyzed molten barium salts. The name Barium comes from the Greek word barys, which means heavy. Barium is a soft, silvery white metal, and has a melting point of 1000 K. Because of its reaction to air, barium cannot be found in nature in its pure form but can be extracted from the mineral barite.

  • Atomic Number = 56        
  • <span">Mass = 137.3 g mol​-1        
  • <span">Electrion Configuration = [Xe]6s2
  • Density = 3.51 g cm-3


Like the lighter members of its family, barium reacts vigorously with water to produce hydrogen gas and so is commonly stored in oil.

Abundance and Extraction

The metal does not occur free in nature but chiefly as the sulfate and carbonate. The sulfate is used in X-ray diagnostics as a contrast medium (i.e., in soft tissue like the digestive tract).

Barium Isotopes

There are seven stable isotopes of naturally occurring barium: 130Ba, 132Ba, 134Ba, 135Ba, 136Ba, 137Ba, and 138Ba. In total, twenty-two isotopes are known to exist, but a majority of them are highly radioactive and have relatively short half-lives. 

Barium Compounds

Barium sulfate (BaSO4), or barite, is the most common mineral abundant in barium. This mineral has a density of 4.5g/cm3 and is extremely insoluble in water. Uses of barium sulfate include being a radiocontrast agent for X-ray imaging of the digestive system. Barium carbonate (BaCO3) is also commonly used as a rat poison. 

Barium compounds (which are toxic) are also useful in pyrotechnic devices where they impart a characteristic green color.