Barium is named after the Greek word barys, meaning "heavy," because barium and its minerals are dense. The pure form of this element was first discovered in 1808 by the chemist Humphry Davy, who extracted it from barium oxide. Davy obtained it by heating the mineral witherite, composed of barium carbonate, BaCO3. Today, the main source of barium is barite, a barium sulfate mineral, BaSO4, which forms in deserts and in rock deposits that come into contact with hot water.

A rarer mineral called benitoite also contains barium. The element is used in spark plugs to make them produce more powerful sparks and is added to glass to increase its luster. Barium compounds are added to some types of clay used to make pots and vases. In oil wells, barium compounds are added to drilling fluids to increase their density. Physicians make use of barium's density by giving patients a solution of barium compound to swallow before taking X-rays of their digestive system. Barium makes the soft digestive organs denser, allowing them to be seen clearly on X-ray radiographs.

Summary of properties (Ba)

Atomic weight137.327(7)
Discoverer (year)Davy, Humphry (1808)
Natural formmetallic solid (body centered cubic)
Electron configuration[Xe] 6s2
Melting point (ºC)725
Boiling point (ºC)1140
Abundance in earth's crust (ppm)425
Isotope (abundance)130Ba (0.106), 132Ba (0.101), 134Ba (2.417), 135Ba (6.592), 136Ba (7.854), 137Ba (11.232), 138Ba (71.698)
Density g/cm33.59
Van der Waals radius (pm)268
Covalent radius (pm)206
Electronegativity (Pauling)0.89
Vaporization enthalpy (kJ/mol)140.00
Enthalpy of fusion (kJ/mol)7.12
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.20
Thermal conductivity (W/cm·K) at 25ºC and 1 atm0.180
Oxidation state+2
Electron affinity (eV)0.14
1st Ionization potential (eV)5.2117

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