|Pronunciation|| / /|
|Appearance||silvery lustrous gray (crystalline),|
brown-black powder (amorphous)
|Standard atomic weight Ar, std(Te)||127.60(3)|
|Tellurium in the periodic table|
|Atomic number (Z)||52|
|Group||group 16 (chalcogens)|
|Electron configuration||[ Kr ] 4d10 5s2 5p4|
|Electrons per shell||2, 8, 18, 18, 6|
|Phase at STP||solid|
|Melting point||722.66 K (449.51 °C,841.12 °F)|
|Boiling point||1261 K(988 °C,1810 °F)|
|Density (near r.t.)||6.24 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 |
|Oxidation states||−2, −1, +1, +2, +3, +4, +5, +6 (a mildly acidic oxide)|
|Electronegativity||Pauling scale: 2.1|
|Atomic radius||empirical:140 pm|
|Covalent radius||138±4 pm|
|Van der Waals radius||206 pm|
|Spectral lines of tellurium|
|Crystal structure|| hexagonal|
|Speed of sound thin rod||2610 m/s(at 20 °C)|
|Thermal expansion||18 µm/(m·K) (at r.t.)|
|Thermal conductivity||1.97–3.38 W/(m·K)|
|Magnetic susceptibility||−39.5·10−6 cm3/mol(298 K)|
|Young's modulus||43 GPa|
|Shear modulus||16 GPa|
|Bulk modulus||65 GPa|
|Brinell hardness||180–270 MPa|
|Naming||after Roman Tellus , deity of the Earth|
|Discovery||Franz-Joseph Müller von Reichenstein (1782)|
|First isolation||Martin Heinrich Klaproth|
|Main isotopes of tellurium|
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth, and partly to tellurium's low affinity for oxygen, which causes it to bind preferentially to other chalcophiles in dense minerals that sink into the core.
Tellurium-bearing compounds were first discovered in 1782 in a gold mine in Kleinschlatten, Transylvania (now Zlatna, Romania) by Austrian mineralogist Franz-Joseph Müller von Reichenstein, although it was Martin Heinrich Klaproth who named the new element in 1798 after the Latin word for "earth", tellus. Gold telluride minerals are the most notable natural gold compounds. However, they are not a commercially significant source of tellurium itself, which is normally extracted as a by-product of copper and lead production.
Commercially, the primary use of tellurium is copper (tellurium copper) and steel alloys, where it improves machinability. Applications in CdTe solar panels and cadmium telluride semiconductors also consume a considerable portion of tellurium production. Tellurium is considered a technology-critical element.
Tellurium has no biological function, although fungi can use it in place of sulfur and selenium in amino acids such as tellurocysteine and telluromethionine.In humans, tellurium is partly metabolized into dimethyl telluride, (CH3)2Te, a gas with a garlic-like odor exhaled in the breath of victims of tellurium exposure or poisoning.
Tellurium has two allotropes, crystalline and amorphous. When crystalline, tellurium is silvery-white with a metallic luster. It is a brittle and easily pulverized metalloid. Amorphous tellurium is a black-brown powder prepared by precipitating it from a solution of tellurous acid or telluric acid (Te(OH)6). 722.66 K (841.12 °F) and 1,261 K (1,810 °F), respectively.Tellurium is a semiconductor that shows a greater electrical conductivity in certain directions depending on atomic alignment; the conductivity increases slightly when exposed to light (photoconductivity). When molten, tellurium is corrosive to copper, iron, and stainless steel. Of the chalcogens (oxygen-family elements), tellurium has the highest melting and boiling points, at
Tellurium adopts a polymeric structure consisting of zig-zag chains of Te atoms. This gray material resists oxidation by air and is not volatile.
Naturally occurring tellurium has eight isotopes. Six of those isotopes, 120Te, 122Te, 123Te, 124Te, 125Te, and 126Te, are stable. The other two, 128Te and 130Te, have been found to be slightly radioactive, × 1024 years for 128Te. This is the longest known half-life among all radionuclides and is about 160 trillion (1012) times the age of the known universe. Stable isotopes comprise only 33.2% of naturally occurring tellurium.with extremely long half-lives, including 2.2
A further 31 artificial radioisotopes of tellurium are known, with atomic masses ranging from 104 to 142 and with half-lives of 19 days or less. Also, 17 nuclear isomers are known, with half-lives up to 154 days. With the exception of beryllium-8 and beta-delayed alpha emission branches in some lighter nuclides, tellurium (104Te to 109Te) is the lightest element with isotopes known to undergo alpha decay.
The atomic mass of tellurium (127.60 g·mol−1) exceeds that of iodine (126.90 g·mol−1), the next element in the periodic table.
With an abundance in the Earth's crust comparable to that of platinum (about 1 µg/kg), tellurium is one of the rarest stable solid elements. In comparison, even the rarest of the stable lanthanides have crustal abundances of 500 µg/kg (see Abundance of the chemical elements).
This rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance. Tellurium is more abundant than rubidium in the cosmos, though rubidium is 10,000 times more abundant in the Earth's crust. The rarity of tellurium on Earth is thought to be caused by conditions during preaccretional sorting in the solar nebula, when the stable form of certain elements, in the absence of oxygen and water, was controlled by the reductive power of free hydrogen. Under this scenario, certain elements that form volatile hydrides, such as tellurium, were severely depleted through evaporation of these hydrides. Tellurium and selenium are the heavy elements most depleted by this process.
Tellurium is sometimes found in its native (i.e., elemental) form, but is more often found as the tellurides of gold such as calaverite and krennerite (two different polymorphs of AuTe2), petzite, Ag3AuTe2, and sylvanite, AgAuTe4. The city of Telluride, Colorado, was named in hope of a strike of gold telluride (which never materialized, though gold metal ore was found). Gold itself is usually found uncombined, but when found as a chemical compound, it is most often combined with tellurium.
Although tellurium is found with gold more often than in uncombined form, it is found even more often combined as tellurides of more common metals (e.g. melonite, NiTe2). Natural tellurite and tellurate minerals also occur, formed by oxidation of tellurides near the Earth's surface. In contrast to selenium, tellurium does not usually replace sulfur in minerals because of the great difference in ion radii. Thus, many common sulfide minerals contain substantial quantities of selenium and only traces of tellurium.
In the gold rush of 1893, miners in Kalgoorlie discarded a pyritic material as they searched for pure gold, and it was used to fill in potholes and build sidewalks. In 1896, that tailing was discovered to be calaverite, a telluride of gold, and it sparked a second gold rush that included mining the streets.
Tellurium (Latin tellus meaning "earth") was discovered in the 18th century in a gold ore from the mines in Kleinschlatten (today Zlatna), near today's city of Alba Iulia, Romania. This ore was known as "Faczebajer weißes blättriges Golderz" (white leafy gold ore from Faczebaja, German name of Facebánya, now Fața Băii in Alba County) or antimonalischer Goldkies (antimonic gold pyrite), and according to Anton von Rupprecht, was Spießglaskönig (argent molybdique), containing native antimony.In 1782 Franz-Joseph Müller von Reichenstein, who was then serving as the Austrian chief inspector of mines in Transylvania, concluded that the ore did not contain antimony but was bismuth sulfide. The following year, he reported that this was erroneous and that the ore contained mostly gold and an unknown metal very similar to antimony. After a thorough investigation that lasted three years and included more than fifty tests, Müller determined the specific gravity of the mineral and noted that when heated, the new metal gives off a white smoke with a radish-like odor; that it imparts a red color to sulfuric acid; and that when this solution is diluted with water, it has a black precipitate. Nevertheless, he was not able to identify this metal and gave it the names aurum paradoxium (paradoxical gold) and metallum problematicum (problem metal), because it did not exhibit the properties predicted for antimony.
In 1789, a Hungarian scientist, Pál Kitaibel, discovered the element independently in an ore from Deutsch-Pilsen that had been regarded as argentiferous molybdenite, but later he gave the credit to Müller. In 1798, it was named by Martin Heinrich Klaproth, who had earlier isolated it from the mineral calaverite.
The 1960s brought an increase in thermoelectric applications for tellurium (as bismuth telluride), and in free-machining steel alloys, which became the dominant use.
The principal source of tellurium is from anode sludges from the electrolytic refining of blister copper. It is a component of dusts from blast furnace refining of lead. Treatment of 1000 tons of copper ore typically yields one kilogram (2.2 pounds) of tellurium.
The anode sludges contain the selenides and tellurides of the noble metals in compounds with the formula M2Se or M2Te (M = Cu, Ag, Au). At temperatures of 500 °C the anode sludges are roasted with sodium carbonate under air. The metal ions are reduced to the metals, while the telluride is converted to sodium tellurite.
Tellurites can be leached from the mixture with water and are normally present as hydrotellurites HTeO3− in solution. Selenites are also formed during this process, but they can be separated by adding sulfuric acid. The hydrotellurites are converted into the insoluble tellurium dioxide while the selenites stay in solution.
The metal is produced from the oxide (reduced) either by electrolysis or by reacting the tellurium dioxide with sulfur dioxide in sulfuric acid.
Commercial-grade tellurium is usually marketed as 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, the tellurium price was driven up by increased demand and limited supply, reaching as high as US$100 per pound in 2006.Despite the expectation that improved production methods will double production, the United States Department of Energy (DoE) anticipates a supply shortfall of tellurium by 2025.
Tellurium is produced mainly in the United States, Peru, Japan and Canada. t, Peru 7 t, Japan 40 t and Canada 16 t.The British Geological Survey gives the following production numbers for 2009: United States 50
Tellurium belongs to the chalcogen (group 16) family of elements on the periodic table, which also includes oxygen, sulfur, selenium and polonium: Tellurium and selenium compounds are similar. Tellurium exhibits the oxidation states −2, +2, +4 and +6, with +4 being most common.
Reduction of Te metal produces the tellurides and polytellurides, Ten2−. The −2 oxidation state is exhibited in binary compounds with many metals, such as zinc telluride, ZnTe, produced by heating tellurium with zinc. Decomposition of ZnTe with hydrochloric acid yields hydrogen telluride (H
2Te), a highly unstable analogue of the other chalcogen hydrides, H
2S and H
2Te is unstable, whereas salts of its conjugate base [TeH]− are stable.
The +2 oxidation state is exhibited by the dihalides, TeCl
2 and TeI
2. The dihalides have not been obtained in pure form, :274 although they are known decomposition products of the tetrahalides in organic solvents, and the derived tetrahalotellurates are well-characterized:
where X is Cl, Br, or I. These anions are square planar in geometry. 281 Polynuclear anionic species also exist, such as the dark brown Te
6, :283 and the black Te
Fluorine forms two halides with tellurium: the mixed-valence Te
4 and TeF
6. In the +6 oxidation state, the –OTeF
5 structural group occurs in a number of compounds such as HOTeF
4 and Te(OTeF
6. The square antiprismatic anion TeF2−
8 is also attested. The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (TeCl
4 and TeI
4) in the +4 state, and other lower halides (Te
2I and two forms of TeI). In the +4 oxidation state, halotellurate anions are known, such as TeCl2−
6 and Te
10. Halotellurium cations are also attested, including TeI+
3, found in TeI
Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of TeSO
3 in vacuum, disproportionating into tellurium dioxide, TeO
2 and elemental tellurium upon heating. Since then, however, existence in the solid phase is doubted and in dispute, although it is known as a vapor fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide.
Tellurium dioxide is formed by heating tellurium in air, where it burns with a blue flame. TeO
3, is obtained by thermal decomposition of Te(OH)
6. The other two forms of trioxide reported in the literature, the α- and γ- forms, were found not to be true oxides of tellurium in the +6 oxidation state, but a mixture of Te4+
2. Tellurium also exhibits mixed-valence oxides, Te
5 and Te
The tellurium oxides and hydrated oxides form a series of acids, including tellurous acid (H
3), orthotelluric acid (Te(OH)
6) and metatelluric acid ((H
n). The two forms of telluric acid form tellurate salts containing the TeO2–
4 and TeO6−
6 anions, respectively. Tellurous acid forms tellurite salts containing the anion TeO2−
When tellurium is treated with concentrated sulfuric acid, the result is a red solution of the Zintl ion, Te2+
4. The oxidation of tellurium by AsF
5 in liquid SO
2 produces the same square planar cation, in addition to the trigonal prismatic, yellow-orange Te4+
Other tellurium Zintl cations include the polymeric Te2+
7 and the blue-black Te2+
8, consisting of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with tungsten hexachloride:
Interchalcogen cations also exist, such as Te
6 (distorted cubic geometry) and Te
8. These are formed by oxidizing mixtures of tellurium and selenium with AsF
5 or SbF
Tellurium does not readily form analogues of alcohols and thiols, with the functional group –TeH, that are called tellurols. The –TeH functional group is also attributed using the prefix tellanyl-.Like H2Te, these species are unstable with respect to loss of hydrogen. Telluraethers (R–Te–R) are more stable, as are telluroxides.
The largest consumer of tellurium is metallurgy in iron, stainless steel, copper, and lead alloys. The addition to steel and copper produces an alloy more machinable than otherwise. It is alloyed into cast iron for promoting chill for spectroscopy, where the presence of electrically conductive free graphite tends to interfere with spark emission testing results. In lead, tellurium improves strength and durability, and decreases the corrosive action of sulfuric acid.
Tellurium is used in cadmium telluride (CdTe) solar panels. National Renewable Energy Laboratory lab tests of tellurium demonstrated some of the greatest efficiencies for solar cell electric power generators. Massive commercial production of CdTe solar panels by First Solar in recent years has significantly increased tellurium demand.Replacing some of the cadmium in CdTe by zinc, producing (Cd,Zn)Te, produces a solid-state X-ray detector, providing an alternative to single-use film badges.
Infrared sensitive semiconductor material is formed by alloying tellurium with cadmium and mercury to form mercury cadmium telluride.
Organotellurium compounds such as dimethyl telluride, diethyl telluride, diisopropyl telluride, diallyl telluride and methyl allyl telluride are precursors for synthesizing metalorganic vapor phase epitaxy growth of II-VI compound semiconductors.Diisopropyl telluride (DIPTe) is the preferred precursor for low-temperature growth of CdHgTe by MOVPE. The greatest purity metalorganics of both selenium and tellurium are used in these processes. The compounds for semiconductor industry and are prepared by adduct purification.
Tellurium, as tellurium suboxide, is used in the media layer of rewritable optical discs, including ReWritable Compact Discs (CD-RW), ReWritable Digital Video Discs (DVD-RW), and ReWritable Blu-ray Discs.
Tellurium dioxide is used to create acousto-optic modulators (AOTFs and AOBSs) for confocal microscopy.
Tellurium is used in the new phase change memory chipsdeveloped by Intel. Bismuth telluride (Bi2Te3) and lead telluride are working elements of thermoelectric devices. Lead telluride is used in far-infrared detectors.
Tellurium has no known biological function, although fungi can incorporate it in place of sulfur and selenium into amino acids such as telluro-cysteine and telluro-methionine.Organisms have shown a highly variable tolerance to tellurium compounds. Many bacteria, such as Pseudomonas aeruginosa , take up tellurite and reduce it to elemental tellurium, which accumulates and causes a characteristic and often dramatic darkening of cells. In yeast, this reduction is mediated by the sulfate assimilation pathway. Tellurium accumulation seems to account for a major part of the toxicity effects. Many organisms also metabolize tellurium partly to form dimethyl telluride, although dimethyl ditelluride is also formed by some species. Dimethyl telluride has been observed in hot springs at very low concentrations.
|GHS Signal word||Danger|
|H317, H332, H360, H412|
|P201, P261, P280, P308+313|
|NFPA 704 (fire diamond)|
Tellurium and tellurium compounds are considered to be mildly toxic and need to be handled with care, although acute poisoning is rare.Tellurium poisoning is particularly difficult to treat as many chelation agents used in the treatment of metal poisoning will increase the toxicity of tellurium. Tellurium is not reported to be carcinogenic.
Humans exposed to as little as 0.01 mg/m3 or less in air exude a foul garlic-like odor known as "tellurium breath". This is caused by the body converting tellurium from any oxidation state to dimethyl telluride, (CH3)2Te. This is a volatile compound with a pungent 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.
People can be exposed to tellurium in the workplace by inhalation, ingestion, skin contact, and eye contact. The Occupational Safety and Health Administration (OSHA) limits (permissible exposure limit) tellurium exposure in the workplace to 0.1 mg/m3 over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set the recommended exposure limit (REL) at 0.1 mg/m3 over an eight-hour workday. In concentrations of 25 mg/m3, tellurium is immediately dangerous to life and health.
The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po). The chemically uncharacterized synthetic element livermorium (Lv) is predicted to be a chalcogen as well. Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper, and the Latinised Greek word genēs, meaning born or produced.
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium – from Ancient Greek σελήνη (selḗnē) "Moon" – was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium.
A metalloid is a type of chemical element which has properties in between, or that are a mixture of, those of metals and nonmetals. There is neither a standard definition of a metalloid nor complete agreement on the elements appropriately classified as such. Despite the lack of specificity, the term remains in use in the literature of chemistry.
In chemistry, a nonmetal is a chemical element that mostly lacks the characteristics of a metal. Physically, a nonmetal tends to have a relatively low melting point, boiling point, and density. A nonmetal is typically brittle when solid and usually has poor thermal conductivity and electrical conductivity. Chemically, nonmetals tend to have relatively high ionization energy, electron affinity, and electronegativity. They gain or share electrons when they react with other elements and chemical compounds. Seventeen elements are generally classified as nonmetals: most are gases ; one is a liquid (bromine); and a few are solids. Metalloids such as boron, silicon, and germanium are sometimes counted as nonmetals.
Tellurium dioxide (TeO2) is a solid oxide of tellurium. It is encountered in two different forms, the yellow orthorhombic mineral tellurite, β-TeO2, and the synthetic, colourless tetragonal (paratellurite), α-TeO2. Most of the information regarding reaction chemistry has been obtained in studies involving paratellurite, α-TeO2.
Selenic acid is the inorganic compound with the formula H
4. It is an oxoacid of selenium, and its structure is more accurately described as (HO)
2. It is a colorless compound. Although it has few uses, its derivative sodium selenate is used in the production of glass and animal feeds.
In chemistry tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.
Selenium dioxide is the chemical compound with the formula SeO2. This colorless solid is one of the most frequently encountered compounds of selenium.
Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water-soluble white solid and a weak reducing agent. Sodium tellurite is an intermediate in the extraction of the element, tellurium; it is a product obtained from anode slimes and is a precursor to tellurium.
Organoselenium compounds are chemical compounds containing carbon-to-selenium chemical bonds. Organoselenium chemistry is the corresponding science exploring their properties and reactivity. Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected.
Dimethyl telluride is an organotelluride compound, formula (CH3)2Te, also known by the abbreviation DMTe.
Mercury telluride (HgTe) is a binary chemical compound of mercury and tellurium. It is a semi-metal related to the II-VI group of semiconductor materials. Alternative names are mercuric telluride and mercury(II) telluride.
Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.
Organotellurium chemistry in chemistry describes the synthesis and properties of chemical compounds containing a carbon to tellurium chemical bond. Organotellurium chemistry was developed in the wake of organoselenium chemistry and, sharing the same group in the periodic table, both chemistries have much in common.
A hexafluoride is a chemical compound with the general formula QXnF6, QXnF6m−, or QXnF6m+. Many molecules fit this formula. An important hexafluoride is hexafluorosilicic acid (H2SiF6), which is a byproduct of the mining of phosphate rock. In the nuclear industry, uranium hexafluoride (UF6) is an important intermediate in the purification of this element.
Cadmium acetate is the chemical compound with the formula Cd(CH3CO2)2. This colourless solid is classified coordination polymer, featuring acetate ligands interconnecting cadmium centers. The compound exists in anhydrous form and as a dihydrate. It forms by treating cadmium oxide with acetic acid:
Gold chalcogenides are compounds formed between gold and one of the chalcogens, elements from group 16 of the periodic table: oxygen, sulfur, selenium, or tellurium.
Molybdenum(IV) telluride, molybdenum ditelluride or just molybdenum telluride is a compound of molybdenum and tellurium with formula MoTe2, corresponding to a mass percentage of 27.32% molybdenum and 72.68% tellurium. It can crystallise in two dimensional sheets which can be thinned down to monolayers that are flexible and almost transparent. It is a semiconductor, and can fluoresce. It is part of a class of materials called transition metal dichalcogenides. As a semiconductor the band gap lies in the infrared region. This raises the potential use as a semiconductor in electronics or an infrared detector.
Hydrogen chalcogenides are binary compounds of hydrogen with chalcogen atoms. Water, the first chemical compound in this series, contains one oxygen atom and two hydrogen atoms, and is the most common compound on the Earth's surface.
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