bismuth

Bismuth is a chemical element with the symbol Bi and the atomic number 83. It is a brittle, crystalline post-transition metal in group 15. Among the heaviest elements found in nature, bismuth-209 has an exceptionally long half-life, so the element has long been treated as effectively stable, though it is technically radioactive.

Its appearance is a pinkish white metal that forms a highly protective oxide film giving an iridescent surface. Bismuth crystallizes in a rhombohedral lattice and is very dense (about 9.78 g/cm3). It has a low melting point for a metal (271.4°C) and a high boiling point (1564°C). The metal is brittle and has relatively low electrical conductivity compared with most metals. It expands slightly on freezing and is diamagnetic.

Native bismuth is rare. The primary ore minerals are bismuthinite (Bi2S3) and bismite (Bi2O3). Bismuth is most commonly recovered as a byproduct of copper, lead, tin, and nickel mining and refining.

Common uses include low-melting fusible alloys with lead or tin, and as a substitute for lead in certain applications due to lower toxicity of many bismuth compounds. Medicinally, bismuth subsalicylate is used for upset stomach, and bismuth oxychloride is used as a cosmetics pigment. Thermoelectric materials based on bismuth telluride and related compounds are important in power generation and cooling. Bismuth alloys also find use in safety devices such as fire sprinkler heads because of their low melting temperatures and non-toxicity.

Safety and environmental notes: Although elemental bismuth and many of its compounds are considered of relatively low toxicity among heavy metals, some salts can cause harm if ingested, inhaled, or accumulated in the body. Proper handling and disposal are advised, and exposure should follow regulatory guidelines.

Name and history: The name bismuth derives from the German Wismut. The element has been known since ancient times, and its isolation as an element occurred in the early modern period.