- Barium (Ba) is a soft, silvery alkaline earth metal with atomic number 56, positioned in Group 2 of the periodic table alongside beryllium, magnesium, calcium, strontium, and radium.
- It has two valence electrons in the 6s subshell, which it readily loses to form the Ba²⁺ ion. Its atomic structure consists of fifty-six protons, usually eighty-one neutrons, and fifty-six electrons arranged in six shells.
- Naturally occurring barium is a mixture of seven stable isotopes, the most abundant being barium-138 (¹³⁸Ba), which accounts for approximately 71.7% of the total.
- Barium is not found in nature in its pure metallic form because of its high reactivity; it oxidizes rapidly in air and reacts readily with water to form barium hydroxide and hydrogen gas. It occurs naturally only in compounds, primarily in the minerals barite (barium sulfate, BaSO₄) and witherite (barium carbonate, BaCO₃). These minerals are mined mainly in China, India, Morocco, and the United States.
- The element was first isolated in 1808 by the English chemist Sir Humphry Davy, who used electrolysis to separate metallic barium from molten barium salts. Its name comes from the Greek barys, meaning “heavy,” reflecting the high density of barium compounds compared to many other minerals.
- In modern applications, barium compounds have important industrial and medical uses. Barite is widely used as a weighting agent in drilling fluids for oil and gas wells, helping to control well pressure. Barium sulfate, due to its opacity to X-rays, is used as a contrast medium in medical imaging of the gastrointestinal tract. Other barium compounds are employed in manufacturing ceramics, specialty glass, and certain pigments. Historically, barium nitrate and barium chlorate were used in green fireworks because barium compounds produce a distinctive green flame.
- Chemically, barium behaves like other alkaline earth metals, forming ionic compounds with nonmetals and being a strong reducing agent. It reacts vigorously with water, acids, and oxygen. Barium hydroxide is a strong base, and barium salts, while useful, can be toxic to humans if soluble, as they interfere with potassium ion transport in biological systems.
- Biologically, barium has no known essential role in humans or animals. Soluble barium compounds are poisonous, causing symptoms such as muscle paralysis, cardiac irregularities, and gastrointestinal distress. However, insoluble compounds like barium sulfate are considered safe for medical imaging because they pass through the digestive system without being absorbed.
- From an environmental perspective, natural barium compounds are generally stable and non-hazardous, but industrial releases of soluble barium salts can contaminate water supplies and pose ecological and health risks. Radioactive isotopes of barium, such as barium-140, are produced in nuclear fission and contribute to short-term fallout hazards.
