Ba

Ba is the chemical element with the symbol Ba and atomic number 56. It is an alkaline earth metal in group 2 of the periodic table, characterized by a soft, silvery-white appearance and high reactivity. In standard conditions it is relatively dense and tarnishes in air; it reacts readily with water and oxygen to form basic oxides and hydroxides. Its common oxidation state is +2.

The name Ba derives from barys, a Greek word meaning heavy, reflecting the element’s relatively high density among the light metals. Barium was first isolated by Humphry Davy in 1808 through the electrolysis of barium oxide. In nature, barium is found mainly in minerals such as barite (barium sulfate, BaSO4) and witherite (barium carbonate, BaCO3). Commercial production typically starts with mining barite, followed by chemical processing to convert BaSO4 to soluble forms like barium chloride, which are then reduced or refined to metallic barium.

Key properties and compounds include BaO, Ba(OH)2, BaCO3, and BaSO4. Barium metal is highly reactive, especially with water, releasing hydrogen gas and forming hydroxides. The most widely used barium compound is barium sulfate, which is virtually insoluble and used as a radiopaque contrast agent in medical X-ray and CT imaging, allowing visualization of the gastrointestinal tract. BaSO4 is also employed in drilling fluids, glassmaking, and certain pigments, while other barium compounds have applications in electronics and specialty chemistry. Historically, barium compounds have served as getters in vacuum tubes and have produced yellow-green colors in pyrotechnics.

Safety is a major consideration: soluble barium compounds are toxic and can interfere with muscle and nerve function, whereas insoluble BaSO4 is generally regarded as safe for medical imaging when properly administered. Environmental handling emphasizes preventing soluble barium from entering water supplies.