Difference between revisions of "Tellurium" - New World Encyclopedia

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'''Tellurium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/tiˈlʊəriəm, tɛ-/}}) (chemical symbol '''Te''', [[atomic number]]* 52) is a relatively rare [[chemical element]] that is classified as a [[metalloid]]. Silver-white in color, it looks like [[tin]]. It is chemically related to [[selenium]] and [[sulfur]]. This element is primarily used in [[alloy]]s and as a [[semiconductor]].
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'''Tellurium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/tiˈlʊəriəm, tɛ-/}}) (chemical symbol '''Te''', [[atomic number]]* 52) is a relatively rare [[chemical element]] that is classified as a [[metalloid]]. Silvery in color, it looks like [[tin]], but its chemical properties are more closely related to those of [[selenium]] and [[sulfur]]. This element is primarily used in [[alloy]]s and as a [[semiconductor]].
  
 
== Occurrence and production ==
 
== Occurrence and production ==
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;See also: [[:Category:Tellurium compounds]]
 
;See also: [[:Category:Tellurium compounds]]
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* '''Silver telluride''' (Ag<sub>2</sub>Te): This compound occurs in nature in the form of the minerals [[hessite]]* and [[empressite]]*. It is a [[semiconductor]] that can be doped to have either n-type or p-type conductivity. On heating, silver is lost from the material.
  
 
== Precautions ==
 
== Precautions ==
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[[Category:Chemical elements]]
 
[[Category:Chemical elements]]
  
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Revision as of 12:57, 20 October 2006

52 antimonytelluriumiodine
Se

Te

Po
Te-TableImage.png
periodic table
General
Name, Symbol, Number tellurium, Te, 52
Chemical series metalloids
Group, Period, Block 16, 5, p
Appearance silvery lustrous gray
Te,52.jpg
Atomic mass 127.60(3) g/mol
Electron configuration [Kr] 4d10 5s2 5p4
Electrons per shell 2, 8, 18, 18, 6
Physical properties
Phase solid
Density (near r.t.) 6.24 g/cm³
Liquid density at m.p. 5.70 g/cm³
Melting point 722.66 K
(449.51 °C, 841.12 °F)
Boiling point 1261 K
(988 °C, 1810 °F)
Heat of fusion 17.49 kJ/mol
Heat of vaporization 114.1 kJ/mol
Heat capacity (25 °C) 25.73 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K     (775) (888) 1042 1266
Atomic properties
Crystal structure hexagonal
Oxidation states ±2, 4, 6
(mildly acidic oxide)
Electronegativity 2.1 (Pauling scale)
Ionization energies
(more)
1st: 869.3 kJ/mol
2nd: 1790 kJ/mol
3rd: 2698 kJ/mol
Atomic radius 140 pm
Atomic radius (calc.) 123 pm
Covalent radius 135 pm
Van der Waals radius 206 pm
Miscellaneous
Magnetic ordering nonmagnetic
Thermal conductivity (300 K)
(1.97–3.38) W/(m·K)
Speed of sound (thin rod) (20 °C) 2610 m/s
Speed of sound (thin rod) (r.t.) 43 m/s
Shear modulus 16 GPa
Bulk modulus 65 GPa
Mohs hardness 2.25
Brinell hardness 180 MPa
CAS registry number 13494-80-9
Notable isotopes
Main article: Isotopes of tellurium
iso NA half-life DM DE (MeV) DP
120Te 0.096% Te is stable with 68 neutrons
122Te 2.603% Te is stable with 70 neutrons
123Te 0.908% >1.0×1013 y ε 0.051 123Sb
124Te 4.816% Te is stable with 72 neutrons
125Te 7.139% Te is stable with 73 neutrons
126Te 18.952% Te is stable with 74 neutrons
128Te 31.687% 2.2×1024 y ββ 0.867 128Xe
130Te 33.799% 7.9×1020 y ββ 2.528 130Xe

Tellurium (IPA: /tiˈlʊəriəm, tɛ-/) (chemical symbol Te, atomic number 52) is a relatively rare chemical element that is classified as a metalloid. Silvery in color, it looks like tin, but its chemical properties are more closely related to those of selenium and sulfur. This element is primarily used in alloys and as a semiconductor.

Occurrence and production

In nature, tellurium is sometimes found in its elemental form, but it is more often found as the tellurides of gold and silver, such as the minerals calaverite, krennerite, petzite, and sylvanite. Tellurium compounds are the only chemical compounds of gold found in nature. Yet, unlike gold, tellurium itself is also found combined with other elements, forming metallic salts.

The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. In addition, it is a component of dusts from blast furnace refining of lead. Tellurium is produced mainly in the United States, Canada, Peru, and Japan.

Commercial-grade tellurium, which is not toxic, is usually marketed as minus 200-mesh powder, but it is also available as slabs, ingots, sticks, and lumps.

History

Tellurium (from the Latin word tellus, meaning "earth") was discovered in 1782 by the Hungarian Franz-Joseph Müller von Reichenstein (Müller Ferenc) in Transylvania. Another Hungarian scientist, Pál Kitaibel, discovered the element independently in 1789, but he later gave the credit to Müller. It was named in 1798 by Martin Heinrich Klaproth who had isolated it earlier.

The 1960s brought growth in thermoelectric applications for tellurium, as well as its use in free-machining steel, which became the dominant use.

Notable characteristics

Tellurium crystal

In the periodic table, tellurium is located in group 16 (formerly group 6A), between selenium and polonium. Along with sulfur, selenium, and polonium, it is a member of the oxygen family of elements, also called the chalcogens. In addition, it lies in period 5, between antimony and iodine.

In its pure and crystalline state, tellurium has a silvery-white color and a metallic luster. When the element is precipitated from a solution of tellurous acid or telluric acid, it appears to have an amorphous form. There is, however, some debate whether this form is really amorphous or composed of minute crystals.

Tellurium is brittle and can be easily pulverized. When burned in air, it produces a greenish-blue flame and forms tellurium dioxide. In its molten state, the element is corrosive toward copper, iron, and stainless steel.

Chemically, tellurium is related to sulfur and selenium and forms similar compounds. Yet, while sulfur and selenium are nonmetals, tellurium (as well as polonium) is classified as a metalloid.

Tellurium is a P-type semiconductor. Its conductivity, which is higher in certain directions, increases slightly on exposure to light. It can be doped with various metals, including tin, copper, silver, and gold.

Isotopes

There are 30 known isotopes of tellurium, with atomic masses ranging from 108 to 137. Naturally occurring tellurium consists of eight isotopes (listed in the table on the right), three of which are radioactive. Among all its radioactive isotopes, 128Te has the longest half-life (2.2×1024 years).

Applications

  • Tellurium is mostly used in alloys with other metals. For example, it is added to lead to improve its strength and durability, and to decrease the corrosive action of sulfuric acid. When added to stainless steel and copper, it makes these metals more workable. It is alloyed with cast iron for chill control.
  • It is used in ceramics.
  • It is also used in chalcogenide glasses.
  • Tellurium is also used in blasting caps.
  • Bismuth telluride (Bi2Te3) is used in thermoelectric devices.
  • Cadmium telluride (CdTe) has potential applications in solar panels. Some of the highest efficiencies for solar cell electric power generation have been obtained by using this material, but this application has not yet caused demand to increase significantly.
  • If some of the cadmium in CdTe is replaced by zinc, then CdZnTe is formed, which is used in solid-state X-ray detectors.
  • When alloyed with both cadmium and mercury, it forms mercury cadmium telluride, an infrared-sensitive semiconductor.

<>Organic tellurides have been employed as initiators for living radical polymerisation and electron-rich mono- and di-tellurides possess antioxidant activity.

Compounds

<>

A compound with metal or hydrogen and similar ions is called a telluride. Good ores of tellurium consist of gold and silver tellurides. Compounds with tellurate ions (TeO42- or TeO66-) are known as tellurates.

See also Cadmium zinc telluride (CdZnTe), Telluric acid (H6TeO6).

See also
Category:Tellurium compounds
  • Silver telluride (Ag2Te): This compound occurs in nature in the form of the minerals hessite and empressite. It is a semiconductor that can be doped to have either n-type or p-type conductivity. On heating, silver is lost from the material.

Precautions

Tellurium and its compounds should be considered to be toxic and need to be handled with care. A human exposed to as little as 0.01 milligram (or less) of tellurium per cubic meter of air develops "tellurium breath," which has a garlicky odor. The body metabolizes tellurium in any oxidation state, converting it to dimethyl telluride. This product is volatile and smells like garlic.

References
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External links

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