Bismuth

Bismuth symbol

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Wismut Kristall und 1cm3 Wuerfel

Bi phase diagram

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Bismuth(III) oxide 2

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Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens with properties resembling its lighter homologs 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 often seen with a pink tinge due to oxidation. Bismuth is the most naturally diamagnetic element, and its thermal conductivity is lower than any metal except mercury. It has a high electrical resistance. When deposited in sufficiently thin layers, bismuth exhibits superconductivity characteristics at low temperatures.

Properties

Bismuth has several notable physical and chemical properties. It has a low melting point (271.5 °C) relative to other metals. Its diamagnetic properties are the strongest of any metal, and it has a low thermal conductivity. Chemically, bismuth forms covalent bonds and is less dense as a liquid than as a solid, which is a characteristic it shares with water, gallium, germanium, antimony, and silicon.

Applications

Bismuth's most well-known application is in pharmaceuticals, particularly in the form of bismuth subsalicylate, used as an antidiarrheal and to treat other stomach ailments. It is also used in cosmetics, pigments, and a few electronic applications due to its non-toxicity compared to other heavy metals. Bismuth alloys, often with low melting points, are used in fire detection and suppression system safety devices. Bismuth's low toxicity is also valued for use in fishing sinkers and shot, as an environmentally friendly alternative to lead.

History

The element was discovered by an unknown alchemist around 1400 AD. The name bismuth comes from the German words "weiße Masse" or "white mass," later anglicized to bismuth. It was often confused with tin and lead until Claude François Geoffroy demonstrated in 1753 that it was distinct from those elements.

Occurrence

Bismuth is relatively scarce in the Earth's crust, occurring at an average concentration of less than 0.2 parts per million. It is produced as a by-product of refining lead, copper, tin, silver, and gold ores. China, Mexico, and Peru are the world's major producers of bismuth.

Compounds

Bismuth forms a variety of compounds with various applications. Bismuth oxychloride is used in cosmetics, while bismuth trioxide is used in fire retardants and the glass industry. Bismuth subsalicylate, as mentioned, is used in medicine. Bismuth compounds are also used in the ceramics industry as pigments and in the production of minor metals through the Kroll process.

Environmental and Health Aspects

Unlike many other heavy metals, bismuth is non-toxic and is considered safe for use in cosmetics and pharmaceuticals. It is one of the least toxic elements on the periodic table, with a toxicity comparable to that of salt. Bismuth's environmental impact is minimal, with its low toxicity making it a preferred choice over more hazardous metals like lead.

See Also

• Post-transition metal
• Diamagnetism
• Superconductivity
• Bismuth subsalicylate

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