2007 Schools Wikipedia Selection. Related subjects: Chemical elements
|Name, Symbol, Number||bismuth, Bi, 83|
|Chemical series||poor metals|
|Group, Period, Block||15, 6, p|
|Appearance||lustrous reddish white
|Atomic mass||208.98040 (1) g/mol|
|Electron configuration||[Xe] 4f14 5d10 6s2 6p3|
|Electrons per shell||2, 8, 18, 32, 18, 5|
|Density (near r.t.)||9.78 g·cm−3|
|Liquid density at m.p.||10.05 g·cm−3|
|Melting point||544.7 K
(271.5 ° C, 520.7 ° F)
|Boiling point||1837 K
(1564 ° C, 2847 ° F)
|Heat of fusion||11.30 kJ·mol−1|
|Heat of vaporization||151 kJ·mol−1|
|Heat capacity||(25 °C) 25.52 J·mol−1·K−1|
|Oxidation states||3, 5
(mildly acidic oxide)
|Electronegativity||2.02 (Pauling scale)|
| Ionization energies
|1st: 703 kJ·mol−1|
|2nd: 1610 kJ·mol−1|
|3rd: 2466 kJ·mol−1|
|Atomic radius||160 pm|
|Atomic radius (calc.)||143 pm|
|Covalent radius||146 pm|
|Electrical resistivity||(20 °C) 1.29 µΩ·m|
|Thermal conductivity||(300 K) 7.97 W·m−1·K−1|
|Thermal expansion||(25 °C) 13.4 µm·m−1·K−1|
|Speed of sound (thin rod)||(20 °C) 1790 m/s|
|Young's modulus||32 GPa|
|Shear modulus||12 GPa|
|Bulk modulus||31 GPa|
|Brinell hardness||94.2 MPa|
|CAS registry number||7440-69-9|
Bismuth ( IPA: [ˈbɪzməθ]) is a chemical element in the periodic table that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony. Of all the metals, it is the most naturally diamagnetic, and only mercury has less thermal conductivity. Lead-free bismuth compounds are used in cosmetics and in medical procedures.
It is a brittle metal with a pinkish hue, often occurring in its native form with an iridescent oxide tarnish showing many refractive colors from yellow to blue. Among the heavy metals, bismuth is unusual in that its toxicity is much lower than that of its neighbors in the periodic table such as lead, thallium and antimony. No other metal is more naturally diamagnetic (as opposed to superdiamagnetic) than bismuth, and it has a high electrical resistance. Of any metal, it has the second lowest thermal conductivity and the highest Hall effect. When deposited in sufficiently thin layers on a substrate, bismuth is a semiconductor, rather than a poor metal . When combusted with oxygen, bismuth burns with a blue flame and its oxide forms yellow fumes. Bismuth expands on freezing, and was long an important component of low-melting typesetting alloys which needed to expand to fill printing molds.
While bismuth was traditionally regarded as the element with the heaviest stable isotope, it had long been thought to be unstable on theoretical grounds. Not until 2003 was this demonstrated when researchers at the Institut d'Astrophysique Spatiale in Orsay, France, measured the alpha emission half-life of 209Bi to be 19 x 1018 years, meaning that bismuth is very slightly radioactive, with a half-life over a billion times longer than the current estimated age of the universe. Due to its extraordinarily long half-life, for nearly all applications bismuth can be treated as if it is stable and non-radioactive. However, the radioactivity is of academic interest because bismuth is one of few elements whose radioactivity was suspected, and indeed theoretically predicted, before being detected in the laboratory.
Though virtually unseen in nature, high-purity bismuth can form into distinctive hopper crystals. These colorful laboratory creations are typically sold to hobbyists.
Bismuth ( New Latin bisemutum from German Wismuth, perhaps from weiße Masse, "white mass") was confused in early times with tin and lead due to its resemblance to those elements. Basilius Valentinus described some of its uses in 1450. Claude François Geoffroy showed in 1753 that this metal is distinct from lead.
Artificial bismuth was commonly used in place of the actual mineral. It was made by hammering tin into thin plates, and cementing them by a mixture of white tartar, saltpeter, and arsenic, stratified in a crucible over an open fire.
In the Earth's crust, bismuth is about twice as abundant as gold. It is not usually economical to mine it as a primary product. Rather, it is usually produced as a byproduct of the processing of other metal ores, especially lead, but also tungsten or other metal alloys.
The most important ores of bismuth are bismuthinite and bismite. The People's Republic of China is the world's largest producer of bismuth, followed by Mexico and Peru. Canada, Bolivia, and Kazakhstan are smaller producers of bismuth.
The average price for bismuth in 2000 was US$ 7.70 per kilogram. It is relatively cheap, since like lead (but to a much lesser extent), it is radiogenic, being formed from the natural decay of uranium and thorium (specifically, by way of neptunium-237 or uranium-233).
Bismuth oxychloride is sometimes used in cosmetics. Also bismuth subnitrate and bismuth subcarbonate are used in medicine. Bismuth subsalicylate (Pepto-Bismol®) is used as an antidiarrheal and to treat some other gastro-intestinal diseases.
Some other current uses are:
- Strong permanent magnets can be made from the alloy bismanol (BiMn).
- Many bismuth alloys have low melting points and are widely used for fire detection and suppression system safety devices.
- Bismuth is used as an alloying agent in production of malleable irons.
- Bismuth is finding use as a catalyst for making acrylic fibers.
- A carrier for U-235 or U-233 fuel in nuclear reactors.
- Bismuth has also been used in solders. The fact that bismuth and many of its alloys expand slightly when they solidify make them ideal for this purpose.
- Bismuth subnitrate is a component of glazes that produces an iridescent luster finish.
- Bismuth telluride is an excellent thermoelectric material; it is widely used.
- As a replacement propellant for xenon in Hall effect thrusters.
In the early 1990s, research began to evaluate bismuth as a nontoxic replacement for lead in various applications:
- As noted above, bismuth has been used in solders; its low toxicity will be especially important for solders to be used in food processing equipment.
- As a pigment in artist's oil paint
- As an ingredient of Ceramic glazes
- As an ingredient in free-machining brasses for plumbing applications
- As an ingredient in free-cutting steels for precision machining properties
- As a catalyst for making acrylic fibres
- In low-melting alloys used in fire detection and extinguishing systems
- As an ingredient in lubricating greases
- As a dense material for fishing sinkers.
- As the oxide, carbonite, or nitrite in crackling microstars ( dragon's eggs) in pyrotechnics.
- In 1997 an antibody conjugate with Bi-213, which has a 45 minute half-life, and decays with the emission of an alpha-particle, was used to treat patients with leukemia.
- As a replacement for lead in shot and bullets. The UK, USA, and many other countries now prohibit the use of lead shot for the hunting of wetland birds, as other creatures in the wetlands are prone to lead poisoning from ingestion of lead shot. Bismuth-tin alloy shot is one alternative that provides similar ballistic performance to lead (another less expensive but also poorer-performing alternative is steel shot, although some prefer it for the increased damgage it does).
Bismuth core bullets are also starting to appear for use in indoor shooting ranges, where particles of lead from the bullet impacting the backstop can be a problem. Due to bismuth's crystaline nature, the bismuth bullets shatter into a non-toxic powder on impact, making recovery and recycling easy. The lack of malleability does, however, make bismuth unsuitable for use in expanding hunting bullets.
- FN Herstal uses bismuth in the projectiles for their FN 303 less-lethal riot gun.