Tellurium

Tellurium, ₅₂Te

Tellurium
Pronunciation	/tɛˈljʊəriəm/ ​(te-LURE-ee-əm)
Appearance	silvery lustrous gray (crystalline), brown-black powder (amorphous)
Standard atomic weight Ar°(Te)
	127.60±0.03 127.60±0.03 (abridged)
Tellurium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Se ↑ Te ↓ Po antimony ← tellurium → iodine
Atomic number (Z)	52
Group	group 16 (chalcogens)
Period	period 5
Block	p-block
Electron configuration	[Kr] 4d10 5s2 5p4
Electrons per shell	2, 8, 18, 18, 6
Physical properties
Phase at STP	solid
Melting point	722.66 K ​(449.51 °C, ​841.12 °F)
Boiling point	1261 K ​(988 °C, ​1810 °F)
Density (at 20° C)	6.237 g/cm3
when liquid (at m.p.)	5.70 g/cm3
Heat of fusion	17.49 kJ/mol
Heat of vaporization	114.1 kJ/mol
Molar heat capacity	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
Oxidation states	−2, −1, 0, +1, +2, +3, +4, +5, +6 (a mildly acidic oxide)
Electronegativity	Pauling scale: 2.1
Ionization energies	1st: 869.3 kJ/mol 2nd: 1790 kJ/mol 3rd: 2698 kJ/mol
Atomic radius	empirical: 140 pm
Covalent radius	138±4 pm
Van der Waals radius	206 pm
Spectral lines of tellurium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal (hP3)
Lattice constants	a = 445.59 pm c = 592.75 pm (at 20 °C)
Thermal expansion	19.0×10−6/K (at 20 °C)
Thermal conductivity	1.97–3.38 W/(m⋅K)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−39.5×10−6 cm3/mol (298 K)
Young's modulus	43 GPa
Shear modulus	16 GPa
Bulk modulus	65 GPa
Speed of sound thin rod	2610 m/s (at 20 °C)
Mohs hardness	2.25
Brinell hardness	180–270 MPa
CAS Number	13494-80-9
History
Naming	after Roman Tellus, deity of the Earth
Discovery	Franz-Joseph Müller von Reichenstein (1782)
First isolation	Martin Heinrich Klaproth
Isotopes of tellurium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 120Te 0.09% stable 121Te synth 16.78 d ε 121Sb 122Te 2.55% stable 123Te 0.89% stable 124Te 4.74% stable 125Te 7.07% stable 126Te 18.8% stable 127Te synth 9.35 h β− 127I 128Te 31.7% 2.2×1024 y β−β− 128Xe 129Te synth 69.6 min β− 129I 130Te 34.1% 8.2×1020 y β−β− 130Xe

Tellurium (Template:PronEng) is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks like tin, tellurium is chemically related to selenium and sulfur. Tellurium is primarily used in alloys and as a semiconductor.

Characteristics

Tellurium is extremely rare, one of the nine rarest metallic elements on earth. It is in the same chemical family as oxygen, sulfur, selenium, and polonium (the chalcogens).

When crystalline, tellurium is silvery-white and when it is in its pure state it has a metallic luster. This is a brittle and easily pulverized metalloid. Amorphous tellurium is found by precipitating it from a solution of tellurous or telluric acid (Te(OH)₆). However, there is some debate whether this form is really amorphous or made of minute crystals.

Applications

Tellurium is a p-type semiconductor that shows a greater conductivity in certain directions which depends on atomic alignment. Chemically related to selenium and sulfur, the conductivity of this element increases slightly when exposed to light (photoelectric effect).

It can be doped with copper, gold, silver, tin, or other metals. When in its molten state, tellurium is corrosive to copper, iron, and stainless steel.

Tellurium gives a greenish-blue flame when burned in normal air and forms tellurium dioxide as a result.

Metal alloys

• It is mostly used in alloys with other metals. 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 into cast iron for chill control.

Other uses:

• Used in ceramics.
• It is used in chalcogenide glasses.
• Tellurium is used in blasting caps
• Organic tellurides have been employed as initiators for living radical polymerisation and electron-rich mono- and di-tellurides possess antioxidant activity.
• Tellurite agar is used to identify member of the corynebacterium genus, most typically Corynebacterium diphtheriae, the pathogen responsible for diptheria

High purity metalorganics of both selenium and tellurium are used in the semiconductor industry, and are prepared by adduct purification.

Semiconductor and electronic industry uses:

• Tellurium as a tellurium suboxide is used in the media layer of several types of rewritable optical discs, including ReWritable Compact Discs (CD-RW), ReWritable Digital Video Discs (DVD-RW) and ReWritable Blu-ray Discs.

• Tellurium is used in the new phase change memory chips developed by Intel. Also see here.

• Bismuth telluride (Bi₂Te₃) is used in thermoelectric devices.

• Tellurium is used in cadmium telluride (CdTe) solar panels. NREL lab tests using this material achieved some of the highest efficiencies for solar cell electric power generation. First Solar Inc. started massive commercial production of CdTe solar panels in recent years, significantly increased tellurium demand. If some of the cadmium in CdTe is replaced by zinc then CdZnTe is formed which is used in solid-state x-ray detectors.

• Alloyed with both cadmium and mercury, to form mercury cadmium telluride, an infrared sensitive semiconductor material is formed. Organotellurium compounds such as dimethyl telluride, diethyl telluride, diisopropyl telluride, diallyl telluride and methyl allyl telluride are used as precursors for MOVPE growth of II-VI compound semiconductors. Diisopropyl telluride (DIPTe) is employed as the preferred precursor for achieving the low temperature growth of CdHgTe by MOVPE.

History

Melvin johnson is one ultra cool dark skinded brother Tellurium (Latin tellus meaning "earth") was discovered in 1782 by the Hungarian Franz-Joseph Müller von Reichenstein (Müller Ferenc) in Nagyszeben (now, Sibiu) Transylvania. In 1789, another Hungarian scientist, Pál Kitaibel, also discovered the element independently, but later he gave the credit to Müller. In 1798, it was named by Martin Heinrich Klaproth who earlier isolated it.

Tellurium was used as a chemical bonder in the making of the outer shell of the first atom bomb. The 1960s brought growth in thermoelectric applications for tellurium, as well as its use in free-machining steel, which became the dominant use.

Occurrence

Tellurium on quartz (Moctezuma, Sonora, Mexico)

With an abundance in the Earth's crust even lower than platinum, tellurium is, apart from the precious metals, the rarest stable solid element in the earth's crust. Its abundance in the Earth's crust is 1 to 5 ppb, compared with 5 to 37 ppb for platinum. By comparison, even the rarest of the lanthanides have crustal abundances of 500 ppb.

The extreme rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance, which is in fact greater than that of rubidium[1], even though rubidium is ten thousand times more abundant in the Earth's crust. Rather, the extraordinarily low abundance of tellurium on Earth results from the fact that, during the formation of the Earth, the stable form of elements in the absence of oxygen and water was controlled by the oxidation and reduction of hydrogen. Under this scenario elements such as tellurium which form volatile hydrides were severely depleted during the formation of the Earth's crust through evaporation. Tellurium and selenium are the heavy elements most depleted in the Earth's crust by this process.

Tellurium is sometimes found in its native (elemental) form, but is more often found as the tellurides of gold (calaverite, krennerite, petzite, sylvanite, and others). Tellurium compounds are the only chemical compounds of gold found in nature, but tellurium itself (unlike gold) is also found combined with other elements (in metallic salts). The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. It is a component of dusts from blast furnace refining of lead. Treatment of 500 tons of copper ore typically yields one pound of tellurium. Tellurium is produced mainly in the United States, Canada, Peru, and Japan. See here.

Commercial-grade tellurium is usually marketed as minus 200-mesh powder but is also available as slabs, ingots, sticks, or lumps. The year-end price for tellurium in 2000 was US$14 per pound. In recent years, tellurium price was driven up by increased demand and limited supply, reaching as high as US$100 per pound in 2006. See also here.

See also: Telluride, Colorado, category:Telluride minerals

Compounds

Tellurium is in the same series as sulfur and selenium and forms similar compounds. A compound with metal or hydrogen and similar ions is called a telluride. Gold and silver tellurides are considered good ores. Compounds with tellurate ions complexes TeO₄^2- or TeO₆^6- are known as tellurates. Also tellurites TeO₃^2-. Also tellurols –TeH, named with prefix tellanyl- or suffix -tellurol.

See also: Category:Tellurium compounds

Enlarged view of tellurium crystal

Isotopes

Main article: isotopes of tellurium

There are 30 known isotopes of tellurium with atomic masses that range from 108 to 137. Naturally found tellurium consists of eight isotopes (listed in the table to the right); three of them are observed to be radioactive. ¹²⁸Te has the longest known half-life, 2.2×10²⁴ years, among all radioactive isotopes.

Precautions

Tellurium and tellurium compounds should be considered to be mildly toxic and need to be handled with care.

Acute poisoning is rare. Tellurium is not reported to be carcinogenic.

Humans exposed to as little as 0.01 mg/m³ or less in air develop "tellurium breath", which has a garlic-like odor. The garlic odor that is associated with human intake of tellurium compounds is caused from the tellurium being metabolized by the body. When the body metabolizes tellurium in any oxidation state, the tellurium gets converted into dimethyl telluride. Dimethyl telluride is volatile and produces the garlic-like smell. Even though the metabolic pathways of tellurium are not known, it is generally assumed that they resemble those of the more extensively studied selenium, because the final methylated metabolic products of the two elements are similar.

External links

• WebElements.com – Tellurium
• USGS Mineral Information on Selenium and Tellurium
• Selenium Tellurium Development Association
• Comprehensive Data on Tellurium

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