The structure of the tellurium atom. World tellurium market Electronic structure of tellurium atom
Tellurium is a non-metal that has a metallic luster. Its color is silvery white. This element is very rare and scattered. It was discovered by the mining inspector Franz Josef Müller in 1782. Tellurium is extracted from polymetallic ore. This substance is contained in the form of compounds in hydrothermal gold deposits and others.
Thallium is a brittle material that acquires plastic properties during heating. The density value of this non-metal is 6.25 g / cm3. Tellium begins to melt when the temperature reaches 450 ° C, and boils at 990 ° C. The material has the properties of a diamagnetic and at 18 ° C the value of the specific magnetic susceptibility is -0.31.10-6.
Tellurium is a p-type semiconductor when ambient conditions are normal or when the material is heated to a boil. When a non-metal is cooled, at a transition around -100 ° C, it changes its properties and acquires n-type conductivity. The forbidden zone in width is 0.34 eV. The transition temperature decreases depending on the purity of the substance.
Thallium is used as an alloying additive in the production of lead. It improves strength and chemical resistance. Lead-tellurium alloy is used in cable and chemical industries. Tellurium is also alloyed with copper and steel. This improves their machining.
Tellurium is also used in glass production. Glass, thanks to such an impurity, acquires a brown color, and its refractive index increases. In the rubber industry, tellurium is used in the rubber vulcanization process.
Significant demand for tellurium is due to its semiconducting properties. It is considered both a typical and a technological semiconductor. This substance is used in microelectronics. It produces a thin film that melts at lower temperatures than many metals.
In its pure form, tellurium, in the form of a semiconductor, is rarely used due to its limited supply in the bowels of the Earth. In most cases, it is used in the manufacture of transistors and devices that are designed to measure the intensity of gamma radiation.
Most often, the industry uses not pure non-metal, but its compounds with metals, which are called tellurides. With their use, important parts of thermoelectric generators are produced.
Sale of non-ferrous metals in Moscow -.
| Tellurium | |
|---|---|
| Atomic number | 52 |
| Appearance of a simple substance | |
| Atom properties | |
| Atomic mass (molar mass) |
127.6 a. e.m. (g / mol) |
| Atom radius | 160 pm |
| Ionization energy (first electron) |
869.0 (9.01) kJ / mol (eV) |
| Electronic configuration | 4d 10 5s 2 5p 4 |
| Chemical properties | |
| Covalent radius | 136 pm |
| Ion radius | (+ 6e) 56 211 (-2e) pm |
| Electronegativity (according to Pauling) |
2,1 |
| Electrode potential | 0 |
| Oxidation states | +6, +4, +2 |
| Thermodynamic properties of a simple substance | |
| Density | 6.24 / cm ³ |
| Molar heat capacity | 25.8 J / (mol) |
| Thermal conductivity | 14.3 W / () |
| Melting temperature | 722,7 |
| Heat of fusion | 17.91 kJ / mol |
| Boiling temperature | 1 263 |
| Heat of vaporization | 49.8 kJ / mol |
| Molar volume | 20.5 cm ³ / mol |
| Crystal lattice of a simple substance | |
| Lattice structure | hexagonal |
| Lattice parameters | 4,450 |
| C / a ratio | 1,330 |
| Debye temperature | n / a |
Tellurium- chemical element with atomic number 52 in the periodic table and atomic mass 127.60; denoted by the symbol Te (Tellurium), belongs to the family of metalloids.
History
It was first found in 1782 in the gold-bearing ores of Transylvania by the mining inspector Franz Josef Müller (later Baron von Reichenstein), on the territory of Austria-Hungary. In 1798 Martin Heinrich Klaproth isolated tellurium and determined its most important properties.
origin of name
From latin tellus, Genitive telluris, Earth.
Being in nature
Native tellurium is also found together with selenium and sulfur (Japanese tellurium sulfur contains 0.17% Te and 0.06% Se).
An important source of tellurium is copper and lead ores.
Receiving
The main source is sludge from electrolytic refining of copper and lead. The sludge is calcined, the tellurium remains in the cinder, which is washed with hydrochloric acid. Tellurium is isolated from the obtained hydrochloric acid solution by passing sulfur dioxide SO 2 through it.
Sulfuric acid is added to separate selenium and tellurium. This precipitates tellurium dioxide TeO 2, and H 2 SeO 3 remains in solution.
Tellurium is reduced from TeO 2 oxide with coal.
To purify tellurium from sulfur and selenium, use is made of its ability, under the action of a reducing agent (Al) in an alkaline medium, to transform into soluble disodium ditelluride Na 2 Te 2:
6Te + 2Al + 8NaOH = 3Na 2 Te 2 + 2Na.
To precipitate tellurium, air or oxygen is passed through the solution:
2Na 2 Te 2 + 2H 2 O + O 2 = 4Te + 4NaOH.
To obtain tellurium of special purity, it is chlorinated
Te + 2Cl 2 = TeCl 4.
The resulting tetrachloride is purified by distillation or rectification. Then the tetrachloride is hydrolyzed with water:
TeCl 4 + 2H 2 O = TeO 2 + 4HCl,
and the formed TeO 2 is reduced with hydrogen:
TeO 2 + 4H 2 = Te + 2H 2 O.
Prices
Tellurium is a rare element, and a significant demand with a small production volume determines its high price (about $ 200-300 per kg, depending on the purity), but, despite this, the range of its applications is constantly expanding.
Physicochemical properties
Tellurium is a fragile silvery-white substance with a metallic luster. In thin layers, red-brown in the light, in pairs - golden-yellow.
Tellurium is chemically less active than sulfur. It dissolves in alkalis, lends itself to the action of nitric and sulfuric acids, but weakly dissolves in dilute hydrochloric acid. Metallic tellurium begins to react with water at 100 ° C, and in the form of a powder it oxidizes in air even at room temperature, forming oxide TeO2.
When heated in air, tellurium burns out, forming Te0 2. This strong compound is less volatile than tellurium itself. Therefore, to purify tellurium from oxides, they are reduced with flowing hydrogen at 500-600 ° C.
In the molten state, tellurium is rather inert; therefore, graphite and quartz are used as container materials for its melting.
Application
Alloys
Tellurium is used in the production of lead alloys with increased ductility and strength (used, for example, in the production of cables). With the introduction of 0.05% tellurium, lead losses due to dissolution under the influence of sulfuric acid are reduced by 10 times, and this is used in the production of lead-acid batteries. It is also important that lead doped with tellurium does not soften during processing by plastic deformation, and this makes it possible to carry out the technology of manufacturing down conductors of battery plates by the method of cold cutting and significantly increase the service life and specific characteristics of the battery.
Thermoelectric materials
Bismuth telluride single crystal
Its role is also great in the production of semiconductor materials and, in particular, tellurides of lead, bismuth, antimony, cesium. In the coming years, the production of lanthanide tellurides, their alloys and alloys with metal selenides for the production of thermoelectric generators with a very high (up to 72–78%) efficiency, which will make it possible to use them in the energy sector and in the automotive industry, will become very important.
So, for example, a very high thermo-EMF was recently discovered in manganese telluride (500 μV / K) and in its combination with selenides of bismuth, antimony and lanthanides, which allows not only to achieve a very high efficiency in thermogenerators, but also to carry out semiconductor refrigerator cooling down to the cryogenic (temperature level of liquid nitrogen) temperatures and even lower. The best tellurium-based material for the production of semiconductor refrigerators in recent years has been tellurium alloy,
Physical propertiesTellurium exists in two modifications - crystalline and amorphous.
Crystalline tellurium is obtained by cooling tellurium vapor, and amorphous tellurium is obtained by reducing telluric acid with sulfur dioxide or another similar reagent:
Amorphous tellurium is a fine black powder that transforms into metallic tellurium when heated. The density of amorphous tellurium is 5.85-5.1 g / cm3.
For crystalline tellurium, two polymorphic species are known: α-Te and β-Te. The α → β transition occurs at 354 ° С. Crystalline tellurium has a white-silver color. Its density is 6.25 g / cm2. The hardness of crystalline tellurium is 2.3; at ordinary temperatures it is brittle, easily crushed into powder, and at higher temperatures it becomes so plastic that it can be pressed.
The melting point of tellurium is 438-452 ° C, and the boiling point is 1390 ° C. Tellurium is characterized by high vapor pressure, which, depending on the temperature, is expressed in the following numbers:
Tellurium has a semiconducting character of conductivity. The electrical resistance of polycrystalline tellurium at 0 ° C is 0.102 ohm * cm. With increasing temperature, the electrical resistivity of tellurium decreases:
In contrast to selenium, the electrical resistance of tellurium is not very sensitive to light. However, at low temperatures, the effect of lighting is still felt; so, at -180 ° C, the electrical resistance of tellurium under the influence of illumination decreases by 70%.
Chemical properties
In terms of its chemical properties, tellurium is similar to selenium, but has a more pronounced metallic character. At room temperature, compact tellurium is resistant to air and oxygen; when heated, it oxidizes and burns with a blue flame with a green border, forming TeO2.
In a dispersed state and in the presence of moisture, tellurium is oxidized at ordinary temperatures. Tellurium at room temperature reacts with halogens and forms chemically stronger halides (TeCl4; TeBr4) than selenium.
Tellurium does not combine with hydrogen directly under normal conditions, but upon heating it forms H2Te. When heated with many metals, tellurium forms tellurides: K2Te, Ag2Te, MgTe, Al2Te, etc.
Metallic tellurium reacts with water at 100-160 ° C, and freshly precipitated (amorphous tellurium) - at room temperature:
Te + 2Н2О → TeO2 + 2Н2.
Tellurium does not dissolve in CS2; dissolves very slowly in dilute HCl. In concentrated and diluted HNO3, tellurium is oxidized to form H2TeO3:
3Те + 4HNО3 + H2O = 3Н2ТеО3 + 4NO.
Tellurous acid is readily decomposed by sulfur dioxide with the release of tellurium:
H2TeO3 + 2SO2 + H2O → Te + 2H2SO4.
This reaction is used to obtain pure tellurium.
Tellurium is an almost constant companion of heavy non-ferrous metals in sulfides (iron and copper pyrite, lead luster), but it also occurs in the form of minerals sylvanite, calaverite (Au, Ag) Te2, etc.
The main source of production of industrial tellurium is the waste of processing sulfide ores of copper and lead - dust, in which tellurium is present in the form of TeO2, obtained during the roasting of sulfide ores; as well as anode sludge obtained during the electrolytic refining of copper and lead.
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Tellurium
TELLURIUM[te], -a; m.[from lat. tellus (telluris) - earth] Chemical element (Te), a brittle crystalline metal of a silvery-gray color (used in the manufacture of brown dyes, semiconductor materials).
◁ Telluric, th, th.
tellurium(lat. Tellurium), chemical element of group VI of the periodic system. Named from lat. tellus, genus. n. telluris - Earth. Silver-gray, very fragile crystals with a metallic luster, density 6.25 g / cm 3, t pl 450 ° C; semiconductor. It is stable in air, at high temperatures it burns with the formation of TeO 2 dioxide. It occurs naturally in the form of tellurides and as native tellurium; often accompanies sulfur and selenium; extracted from copper electrolysis waste. Alloy component (copper, lead, cast iron); dye for glass and ceramics (brown). Many tellurium compounds are semiconductor materials, infrared receivers.
TELLURIUMTELLURUS (Latin Tellurium from Latin tellus - Earth), Te (read "tellurium"), a chemical element with atomic number 52, atomic mass 127.60. Natural tellurium consists of eight stable isotopes: 120 Te (content 0.089% by mass), 122 Te (2.46%), 123 Te (2.46%), 124 Te (4.74%), 125 Te (7, 03%), 126 Te (18.72%), 128 Te (31.75%) and 130 Te (34.27%). The radius of the atom is 0.17 nm. Ion radii: Te 2– - 0.207 nm (coordination number 6), Te 4+ - 0.066 nm (3), 0.08 nm (4), 0.111 nm (6), Te 6+ - 0.057 (4) and 0.070 nm (6). Sequential ionization energies: 9.009, 18.6, 28.0, 37.42 and 58.8 eV. Located in group VIA, in the 5th period of the periodic table of elements. Chalcogen (cm. CHALCOGENS)
,
non-metal. Configuration of the outer electron layer 5 s 2
p 4
... Oxidation states: –2, +2, +4, +6 (valencies II, IV and VI). Pauling electronegativity (cm. POLING Linus)
2,10.
Tellurium is a fragile silvery-white substance with a metallic luster.
Discovery history
It was first discovered in 1782 in the gold-bearing ores of Transylvania by the mining inspector F.I.Müller, who took it for a new metal. In 1798 M.G. Klaprot (cm. KLAPROT Martin Heinrich)
isolated tellurium and determined its most important properties.
Being in nature
The content in the earth's crust is 1 · 10 -6% by weight. About 100 tellurium minerals are known. The most important of them: altaite PbTe, sylvanite AgAuTe 4, calaverite AuTe 2, tetradymite Bi 2 Te 2 S. There are oxygen compounds of tellurium, for example TeO 2 - telluric ocher. Native tellurium is also found together with selenium (cm. SELENIUM)
and gray (cm. SULFUR)
(Japanese tellurium sulfur contains 0.17% Te and 0.06% Se).
An important source of tellurium is copper and lead ores.
Receiving
Primary source - copper electrolytic refining sludge (cm. COPPER)
and lead. (cm. LEAD)
The sludge is calcined, the tellurium remains in the cinder, which is washed with hydrochloric acid. Tellurium is isolated from the obtained hydrochloric acid solution by passing sulfur dioxide SO 2 through it.
Sulfuric acid is added to separate selenium and tellurium. In this case, tellurium dioxide TeO 2 precipitates, and selenous acid remains in solution.
To isolate Te from the slimes, they are sintered with soda, followed by leaching. Those passes into an alkaline solution, from which, upon neutralization, it precipitates in the form of TeO 2:
Na 2 TeO 3 + 2HC = TeO 2 Ї + 2NaCl.
Tellurium is reduced from TeO 2 oxide with coal.
To purify tellurium from S and Se, use is made of its ability, under the action of a reducing agent (Al) in an alkaline medium, to transform into soluble disodium ditelluride Na 2 Te 2:
6Te + 2Al + 8NaOH = 3Na 2 Te 2 + 2Na.
To precipitate tellurium, air or oxygen is passed through the solution:
2Na 2 Te 2 + 2H 2 O + O 2 = 4Te + 4NaOH.
To obtain tellurium of special purity, it is chlorinated:
Te + 2Cl 2 = TeCl 4.
The resulting tetrachloride is purified by distillation or rectification. Then the tetrachloride is hydrolyzed with water:
TeCl 4 + 2H 2 O = TeO 2 Ї + 4HCl,
and the formed TeO 2 is reduced with hydrogen:
TeO 2 + 4H 2 = Te + 2H 2 O.
Physical and chemical properties
Thallur is a fragile silvery-white substance with a metallic luster. The crystal lattice is hexagonal, a= 0.44566 nm, c= 0.59268 nm. The structure consists of parallel spiral chains. Density 6.247 g / cm 3. Melting point 449.8 ° C, boiling point 990 ° C. In thin layers, red-brown in the light, in pairs - golden-yellow.
P-type semiconductor. The band gap is 0.32 eV. Electrical conductivity increases with lighting.
During precipitation, amorphous tellurium is released from solutions, the density is 5.9 g / cm 3. At 4.2 GPa and 25 ° C, a modification with a b-Sn (Te-II) type structure is formed. At 6.3 GPa, the Te-III modification with a rhombohedral structure was obtained. Te-II and Te-III exhibit the properties of metals.
Stable in air at room temperature, even in a finely dispersed state. When heated in air, it burns with a bluish-green flame with the formation of TeO 2 dioxide. Standard half-reaction potential:
TeO 3 2– + 3H 2 O + 4e = Te + 6OH -: 0.56V.
At 100–160 ° C it is oxidized by water:
Te + 2H 2 O = TeO 2 + 2H 2
When boiled in alkaline solutions, tellurium disproportionates to the formation of telluride and tellurite:
8Te + 6KOH = 2K 2 Te + K 2 TeO 3 + 3H 2 O.
Te does not react with hydrochloric and dilute sulfuric acids. Concentrated H 2 SO 4 dissolves Te, the resulting Te 4 2+ cations color the solution red. Diluted HNO 3 oxidizes Te to tellurous acid H 2 TeO 3:
3Te + 4HNO 3 + H 2 O = 3H 2 TeO 3 + 4NO.
Strong oxidants (HClO 3, KMnO 4) oxidize Te to weak telluric acid H 6 TeO 6:
Te + HClO 3 + 3H 2 O = HCl + H 6 TeO 6.
With halogens (cm. HALOGENS)
(except for fluorine) forms tetrahalides. Fluorine oxidizes Te to TeF6 hexafluoride.
Hydrogen telluride H 2 Te is a colorless poisonous gas with an unpleasant odor formed during hydrolysis of tellurides.
Tellurium compounds (+2) are unstable and prone to disproportionation:
2TeCl 2 = TeCl 4 + Te.
Application
The main application of Te and its compounds is in semiconductor technology. Te additives in cast iron (cm. CAST IRON)
and steel (cm. STEEL)
, lead (cm. LEAD)
or copper increases their mechanical and chemical resistance. Those and its compounds are used in the production of catalysts, special glasses, insecticides, herbicides.
Physiological action
Tellurium and its volatile compounds are toxic. Ingestion causes nausea, bronchitis, pneumonia. MPC in air 0.01 mg / m 3, in water 0.01 mg / l. In case of poisoning, tellurium is excreted from the body in the form of disgusting-smelling organo-tellurium compounds.
Trace amounts of Te are always found in living organisms, and its biological role has not been clarified.
encyclopedic Dictionary. 2009 .
Synonyms:See what "tellurium" is in other dictionaries:
- (new lat., from lat. Tellus, Telluris earth, goddess of the earth). A simple body, similar to sulfur in its properties of compounds, was discovered in gold ore in 1872 and belongs to metals and metalloids. Dictionary of foreign words included in the Russian language. ... ... Dictionary of foreign words of the Russian language
M l, Te. Trig. Gab. prisms, up to needle-like. Sp. owls. along the prism. Agr .: fine-grained and columnar. Tin white. Bl. metal. TV. 2 2.5. Ud. v. 6.3. In hydrotherm. veins with native Au, tellurides Au and Ag, sulfides. Geological ... ... Geological encyclopedia
- (lat. Tellurium) Those, chemical element of group VI of the periodic system, atomic number 52, atomic mass 127.60. Name from lat. tellus genus. n. telluris Earth. Silvery gray, very fragile crystals with a metallic luster, density 6.24 ... ... Big Encyclopedic Dictionary
Tellurium, chalcogen, sylvan Dictionary of Russian synonyms. tellurium n., number of synonyms: 8 mineral (5627) ... Synonym dictionary
TELLURIUM- TELLURIUM, Tellurium, chem. The symbol Te ranks 52nd in the periodic table. Homologue of sulfur and selenium (group VІ). At. weight 127.5. T. amorphous black powder or brittle lumps of silver-white color, with a metallic luster; beats weight 6,24, t ° ... ... Great medical encyclopedia
- (Tellurium), Te, chemical element of group VI of the periodic table, atomic number 52, atomic mass 127.60; refers to chalcogenes; non-metal. Highlighted by the Hungarian scientist F. Müller von Reichenstein in 1782 ... Modern encyclopedia
- (symbol Te), a silvery white chemical element, discovered in 1782. It occurs naturally in combination with gold in sylvanite. Its main source is a by-product of the electrolytic refining of copper. The shiny, fragile element is used in ... Scientific and technical encyclopedic dictionary
Tellurium, tellurium, pl. no, husband. (from Latin tellus earth) (chem.). Chemical element, crystalline substance, silvery white. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary