Bismuth



Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth chemically resembles arsenic and antimony. Elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when freshly produced, but is often seen in air with a pink tinge owing to surface oxidation. Bismuth is the most naturally diamagnetic element, and has one of the lowest values of thermal conductivity among metals.

Bismuth metal has been known on Terra from ancient times, although until the 18th century CE it was often confused with lead and tin, which share some physical properties.

Bismuth has long been considered as the element with the highest atomic mass that is stable. However, in 2003 OTT it was discovered to be slightly radioactive: its only primordial isotope, bismuth-209, decays with a half life more than a billion times the estimated age of the universe.

Bismuth compounds account for about half the production of bismuth. They are used in cosmetics, pigments, and a few pharmaceuticals. Bismuth's unusual propensity to expand upon freezing is responsible for some of its uses, such as in casting of printing type. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead became apparent, there was an increasing use of bismuth alloys (presently about a third of bismuth production) as a replacement for lead.

Today, cosmetics and alloys account for 99% of bismuth production.