Bismuth

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83 leadbismuthpolonium
Sb

Bi

Uup
Bi-TableImage.png
General
Name, Symbol, Number bismuth, Bi, 83
Chemical series poor metals
Group, Period, Block 15, 6, p
Appearance lustrous reddish white
Bismuth crystal macro.jpg
Atomic mass 208.98040(1) g/mol
Electron configuration [Xe] 4f14 5d10 6s2 6p3
Electrons per shell 2, 8, 18, 32, 18, 5
Physical properties
Phase solid
Density (near r.t.) 9.78 g/cm³
Liquid density at m.p. 10.05 g/cm³
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
Heat of vaporization 151 kJ/mol
Heat capacity (25 °C) 25.52 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 941 1041 1165 1325 1538 1835
Atomic properties
Crystal structure rhombohedral
Oxidation states 3, 5
(mildly acidic oxide)
Electronegativity 2.02 (Pauling scale)
Ionization energies
(more)
1st: 703 kJ/mol
2nd: 1610 kJ/mol
3rd: 2466 kJ/mol
Atomic radius 160 pm
Atomic radius (calc.) 143 pm
Covalent radius 146 pm
Miscellaneous
Magnetic ordering diamagnetic
Electrical resistivity (20 °C) 1.29 µΩ·m
Thermal conductivity (300 K) 7.97 W/(m·K)
Thermal expansion (25 °C) 13.4 µm/(m·K)
Speed of sound (thin rod) (20 °C) 1790 m/s
Speed of sound (thin rod) (r.t.) 32 m/s
Shear modulus 12 GPa
Bulk modulus 31 GPa
Poisson ratio 0.33
Mohs hardness 2.25
Brinell hardness 94.2 MPa
CAS registry number 7440-69-9
Notable isotopes
Main article: Isotopes of bismuth
iso NA half-life DM DE (MeV) DP
207Bi syn 31.55 y ε, β+ 2.399 207Pb
208Bi syn 3,368,000 y ε, β+ 2.880 208Pb
209Bi 100% (1.9±0.2) ×1019y α   205Tl

Bismuth (chemical symbol Bi, atomic number 83) is a brittle, white crystalline metal with a pink tinge. It acquires an iridescent oxide tarnish that shows many refractive colors, ranging from yellow to blue. It belongs to the same family of chemical elements as arsenic and antimony and is chemically similar to them. It is a poor conductor of heat and electricity.

This element expands on freezing and was long an important component of low-melting typesetting alloys that needed to expand to fill printing molds. Currently, bismuth alloys are widely used for safety devices in fire detection and suppression systems. Bismuth oxychloride is used extensively in cosmetics; bismuth subnitrate, subcarbonate, and subsalicylate are useful for medical applications; and bismuth telluride is used as a thermoelectric material. In addition, bismuth is being used as a nontoxic replacement for lead in various applications, including solder, paints, bullets and shot, brasses for plumbing, and fishing sinkers.

Contents

Occurrence

In the Earth's crust, bismuth is about twice as abundant as gold. In nature, it occurs in its native (free elemental) form, and also as its compounds. It is often associated with the ores of lead, tin, and copper. Its most important ores are bismuthinite (a sulfide) and bismite (an oxide).

It is usually not economical to mine bismuth as a primary product. Rather, it is most often obtained as a byproduct of the processing of other metal ores, especially lead, or other metal alloys. Like lead (but to a much lesser extent), it is radiogenic, being formed from the natural radioactive decay of uranium and thorium (specifically, by the decay of neptunium-237 or uranium-233).

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 this element.

History

Bismuth (New Latin bisemutum, from German Wismuth, perhaps from weiße Masse, "white mass") was confused in early times with tin and lead because of its resemblance to those elements. The German monk Basilius Valentinus described some of its uses in 1450. In 1753, Claude François Geoffroy showed that this metal is distinct from lead.

Artificial bismuth was commonly used in place of the actual mineral. It was made by reducing tin into thin plates and cementing them by a mixture of white tartar, saltpeter, and arsenic, stratified in a crucible over an open fire.[1]

Notable characteristics

In the periodic table, bismuth is located in group 15 (formerly group 5A), below arsenic and antimony. It is thus a member of the nitrogen family of elements, sometimes called the pnictogens (or pnicogens). It lies in period 6, between lead and polonium in period 6. In addition, bismuth is placed in the group called "poor metals" (or post-transition metals), which are situated between the transition metals and metalloids in the periodic table. The melting and boiling points of this group of metals are generally lower than those of the transition metals, and they are also softer.

Among all the metals, bismuth is the most naturally diamagnetic—in other words, it is the most resistant to being magnetized. Also, it has a high electrical resistance. Its thermal conductivity is nearly the lowest among metals—only mercury has a lower value for this property. The toxicity of bismuth is much lower than that of its neighbors in the periodic table, such as lead, thallium, and antimony.

When deposited in sufficiently thin layers on a substrate bismuth acts as a semiconductor, rather than as a poor metal [2]. When bismuth is burned with oxygen, the flame acquires a blue color, and the bismuth trioxide produced forms yellow fumes.

Though virtually unseen in nature, high-purity bismuth can be artificially produced in the form of distinctive "hopper crystals"—the edges of the crystals are fully developed, but the interior spaces are not filled in. (Such a crystal is shown in the table on the right.) These colorful laboratory creations are typically sold to hobbyists.

Isotopes

Many isotopes of bismuth are known, ranging in mass number from 184 to 218, most of which are extremely short-lived. Until recently, bismuth-209 was regarded as the heaviest stable isotope of any element. It was, however, suspected to be radioactive on theoretical grounds. Finally, in 2003, researchers at the Institut d'Astrophysique Spatiale in Orsay, France, demonstrated that 209Bi is very slightly radioactive, with a half-life of about 1.9 × 1019 years. This figure is over a billion times longer than the current estimated age of the universe. Given this phenomenal half-life, 209Bi can be treated as if it is stable and nonradioactive. Ordinary food containing typical amounts of carbon-14 is many thousands of times more radioactive than bismuth, as are our own bodies. Nonetheless, the radioactivity is of academic interest because bismuth is one of few elements whose radioactivity was theoretically predicted before being detected in the laboratory.

Compounds

  • Bismuth subsalicylate: It displays anti-inflammatory action (by the salicylate) and also acts as an antacid, anti-diarrheal, and mild antibiotic. It is the active ingredient in medications such as Pepto-Bismol® and Kaopectate®. It can, however, cause a black tongue and black stools in some users of the drugs.
  • Bismuth(III) telluride (Bi2Te3): This compound is a semiconductor and an efficient thermoelectric material for devices used in refrigeration or portable power generation. Although generally a low-risk material, it can be fatal if large doses are ingested. One should avoid breathing its dust. Also, its reaction with water may release toxic fumes.
  • Bismuth trioxide (Bi2O3): Like other metal oxides, it is a chemically basic oxide. It is the most important industrial compound of bismuth and a starting point for bismuth chemistry. It is found naturally as the mineral bismite, but it is usually obtained as a byproduct of the smelting of copper and lead ores. It may also be prepared by burning bismuth metal in air. It is commonly used to produce the "Dragon's eggs" effect in fireworks.
  • Bismuth germanate (BGO, Bi4Ge3O12, or the less common type Bi12GeO20): This compound is mainly used as a scintillator, because it emits light (with peak wavelength at 480 nm) when subjected to high-energy gamma rays. It is used in detectors in various fields of study, including particle physics, aerospace physics, nuclear medicine, and geologic exploration. It is also used in detectors for positron emission tomography.

Applications

Bismuth and its compounds have many applications, a number of which are listed below.

  • Bismuth oxychloride is extensively used in cosmetics.
  • Bismuth subnitrate and subcarbonate are used in medicine.
  • Bismuth subsalicylate is the active ingredient in certain antacids and antidiarrheal agents, as noted above.
  • Bismuth telluride is an excellent thermoelectric material and is widely used.
  • Strong, permanent magnets can be made from the manganese-bismuth alloy called bismanol.
  • Many bismuth alloys have low melting points and are widely used in safety devices for fire detection and suppression.
  • Bismuth is used in producing malleable irons.
  • It is finding use as a catalyst for making acrylic fibers.
  • It is a carrier for U-235 or U-233 fuel in nuclear reactors.
  • Bismuth subnitrate is a component of glazes, producing an iridescent luster finish.

In the early 1990s, research began to evaluate bismuth as a nontoxic replacement for lead in various applications:

  • In lead-free solders. Bismuth and many of its alloys expand slightly when they solidify, making them ideal for use in solders. This element's low toxicity will be especially important for solders intended for use in food-processing equipment.
  • As a pigment in artist's oil paints.
  • 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 fibers.
  • 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, subcarbonate, or subnitrate in pyrotechnics (for "crackling microstars" or "dragon's eggs").
  • As a replacement for lead in shot and bullets. Several countries (including the United Kingdom and the United States) prohibit the use of lead shot for the hunting of wetland birds, which are prone to poisoning from ingestion of the shot. Bismuth shot is one alternative that provides similar ballistic performance. Also, bismuth core bullets are being used in indoor shooting ranges, to avoid the generation of lead particles when a bullet strikes the backstop. Given bismuth's crystalline nature, bismuth bullets shatter into a nontoxic powder on impact, making recovery and recycling easy. The lack of malleability, however, makes bismuth unsuitable for use in expanding hunting bullets.

See also

References

  1. This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain. [1]
  2. Hoffman, C. A., J. R. Meyer, F. J. Bartoli, A. Di Venere, X. J. Yi, C. L. Hou, H. C. Wang, J. B. Ketterson, and G. K. Wong. “Semimetal-to-semiconductor transition in bismuth thin films.” Phys. Rev. B 48: 11431 (1993). Digital object identifier (DOI): 10.1103/PhysRevB.48.11431

External links

All links retrieved February 6, 2013.

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