|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/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)|
|Oxidation states||3, 5
(mildly acidic oxide)
|Electronegativity||2.02 (Pauling scale)|
|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|
|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|
|Brinell hardness||94.2 MPa|
|CAS registry number||7440-69-9|
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.
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).
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.
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 . 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.
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.
Bismuth and its compounds have many applications, a number of which are listed below.
In the early 1990s, research began to evaluate bismuth as a nontoxic replacement for lead in various applications:
All links retrieved February 6, 2013.
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