Tellurium metal. The structure of the tellurium atom
It is unlikely that anyone will believe the story of a sea captain who, in addition, is a professional circus wrestler, a well-known metallurgist and a consulting physician in a surgical clinic. In the world of chemical elements, such a variety of professions is a very common phenomenon, and Kozma Prutkov's expression is inapplicable to them: "A specialist is like a flux: his fullness is one-sided." Let us recall (even before talking about the main object of our story) iron in cars and iron in blood, iron - a magnetic field concentrator and iron - an integral part of ocher ... True, sometimes it took much more time to "professional training" of the elements than to prepare intermediate yoga. So element No. 52, which we are about to tell, was used for many years only to demonstrate what it really is, this element, named after our planet: "tellurium" - from tellus, which in Latin means "Earth ".
This element was discovered almost two centuries ago. In 1782, the mining inspector Franz Josef Müller (later Baron von Reichenstein) examined the gold ore found in Semigorye, on the territory of the then Austria-Hungary. It turned out to be so difficult to decipher the composition of the ore that it was called Aurumaticum - “doubtful gold”. It was from this "gold" that Muller isolated a new metal, but there was no complete certainty that it was really new. (Later it turned out that Müller was wrong about something else: the element he discovered was new, but it can only be classified as a metal with a big stretch.)
To dispel doubts, Müller turned to a prominent specialist, the Swedish mineralogist and analytical chemist Bergman, for help.
Unfortunately, the scientist died before he could finish the analysis of the sent substance - in those years, analytical methods were already quite accurate, but the analysis took a very long time.
Other scientists tried to study the element discovered by Muller, but only 16 years after its discovery, Martin Heinrich Klaproth, one of the greatest chemists of that time, irrefutably proved that this element was actually new, and proposed the name "tellurium" for it.
As always, after the discovery of the element, the search for its applications began. Apparently, proceeding from the old principle, dating back to the times of iatrochemistry - the world is a pharmacy, the Frenchman Fournier tried to treat some serious diseases with tellurium, in particular leprosy. But without success - only many years later Tellurium was able to provide doctors with some "minor services". More precisely, not tellurium itself, but salts of tellurous acid K 2 Te0 3 and Na 2 Te0 3, which began to be used in microbiology as dyes that impart a certain color to the studied bacteria. So, with the help of tellurium compounds, a diphtheria bacillus is reliably isolated from a mass of bacteria. If not in treatment, then at least in diagnosis, element No. 52 turned out to be useful to doctors.
But sometimes this element, and even more so some of its compounds, add trouble to doctors. Tellurium is quite toxic. In our country, the maximum allowable concentration of tellurium in the air is 0.01 mg/m3. Of the tellurium compounds, the most dangerous is hydrogen telluride H 2 Te, a colorless poisonous gas with an unpleasant odor. The latter is quite natural: tellurium is an analogue of sulfur, which means that H 2 Te should be similar to hydrogen sulfide. It irritates the bronchi, adversely affects the nervous system.
These unpleasant properties did not prevent tellurium from entering technology and acquiring many "professions".
Metallurgists are interested in tellurium because even small additions to lead greatly increase the strength and chemical resistance of this important metal. Lead doped with tellurium is used in the cable and chemical industries. Thus, the service life of sulfuric acid production apparatuses coated on the inside with a lead-tellurium alloy (up to 0.5% Te) is twice as long as that of similar apparatuses lined with lead alone. The addition of tellurium to copper and steel facilitates their machining.
In the glass industry, tellurium is used to give the glass a brown color and a higher refractive index. In the rubber industry, as an analogue of sulfur, it is sometimes used to vulcanize rubbers.
Tellurium - semiconductor
However, these industries were not responsible for the jump in prices and demand for element No. 52. This jump took place in the early 60s of our century. Tellurium is a typical semiconductor, and a technological semiconductor. Unlike germanium and silicon, it is relatively easy to melt (melting point 449.8 ° C) and evaporate (boils at a temperature just below 1000 ° C). From it, therefore, it is easy to obtain thin semiconductor films, which are of particular interest to modern microelectronics.
However, pure tellurium as a semiconductor is used to a limited extent - for the manufacture of field-effect transistors of some types and in devices that measure the intensity of gamma radiation. Moreover, an impurity of tellurium is deliberately introduced into gallium arsenide (the third most important semiconductor after silicon and germanium) in order to create electronic type conductivity in it.
The scope of some tellurides, compounds of tellurium with metals, is much wider. Bismuth Bi 2 Te 3 and antimony Sb 2 Te 3 tellurides have become the most important materials for thermoelectric generators. To explain why this happened, let's make a small digression into the field of physics and history.
A century and a half ago (in 1821), the German physicist Seebeck discovered that in a closed electrical circuit consisting of different materials, the contacts between which are at different temperatures, an electromotive force is created (it is called thermo-EMF). After 12 years, the Swiss Peltier discovered an effect opposite to the Seebeck effect: when an electric current flows through a circuit made up of different materials, at the points of contact, in addition to the usual Joule heat, a certain amount of heat is released or absorbed (depending on the direction of the current).
For about 100 years, these discoveries remained a "thing in itself", curious facts, nothing more. And it would not be an exaggeration to say that a new life for both of these effects began after Academician A.F. Ioffe and his coworkers developed the theory of the use of semiconductor materials for the manufacture of thermoelements. And soon this theory was embodied in real thermoelectric generators and thermoelectric refrigerators for various purposes.
In particular, thermoelectric generators, in which bismuth, lead and antimony tellurides are used, provide energy to artificial satellites of the Earth, navigation and meteorological installations, cathodic protection devices for main pipelines. The same materials help maintain the desired temperature in many electronic and microelectronic devices.
In recent years, another chemical compound of tellurium with semiconductor properties, cadmium telluride CdTe, has attracted great interest. This material is used for the manufacture of solar cells, lasers, photoresistors, counters of radioactive radiation. Cadmium telluride is also famous for being one of the few semiconductors in which the Hahn effect is noticeably manifested.
The essence of the latter lies in the fact that the very introduction of a small plate of the corresponding semiconductor into a sufficiently strong electric field leads to the generation of high-frequency radio emission. The Hahn effect has already found application in radar technology.
In conclusion, we can say that quantitatively the main "profession" of tellurium is the alloying of lead and other metals. Qualitatively, the main thing, of course, is the work of tellurium and tellurides as semiconductors.
Useful admixture
In the periodic table, the place of tellurium is in the main subgroup of group VI, next to sulfur and selenium. These three elements are similar in chemical properties and often accompany each other in nature. But the proportion of sulfur in the earth's crust is 0.03%, selenium is only 10-5%, and tellurium is even an order of magnitude smaller - 10~6%. Naturally, tellurium, like selenium, is most often found in natural sulfur compounds - as an impurity. It happens, however (remember the mineral in which tellurium was discovered), that it is in contact with gold, silver, copper and other elements. More than 110 deposits of forty tellurium minerals have been discovered on our planet. But it is always mined at the same time either with selenium, or with gold, or with other metals.
In Russia, copper-nickel tellurium-bearing ores of Pechenga and Monchegorsk, tellurium-bearing lead-zinc ores of Altai and a number of other deposits are known.
Tellurium is isolated from copper ore at the stage of blister copper purification by electrolysis. A precipitate falls to the bottom of the electrolyzer - sludge. This is a very expensive semi-finished product. For illustration, the composition of the sludge from one of the Canadian plants is given: 49.8% copper, 1.976% gold, 10.52% silver, 28.42% selenium and 3.83% tellurium. All these valuable components of the sludge must be separated, and there are several ways to do this. Here is one of them.
The sludge is melted in a furnace and air is passed through the melt. Metals, except for gold and silver, oxidize, turn into slag. Selenium and tellurium are also oxidized, but into volatile oxides, which are captured in special apparatuses (scrubbers), then dissolved and converted into acids - selenous H 2 SeOz and tellurous H 2 TeOz. If sulfur dioxide gas S0 2 is passed through this solution, reactions will occur
H 2 Se0 3 + 2S0 2 + H 2 0 → Se ↓ + 2H 2 S0 4 .
H2Te03 + 2S02 + H20 → Te ↓ + 2H 2 S0 4 .
Tellurium and selenium fall out at the same time, which is very undesirable - we need them separately. Therefore, the process conditions are selected in such a way that, in accordance with the laws of chemical thermodynamics, primarily selenium is reduced first. This is helped by the selection of the optimal concentration of hydrochloric acid added to the solution.
Then tellurium is precipitated. The precipitated gray powder, of course, contains a certain amount of selenium and, in addition, sulfur, lead, copper, sodium, silicon, aluminum, iron, tin, antimony, bismuth, silver, magnesium, gold, arsenic, chlorine. Tellurium has to be purified from all these elements first by chemical methods, then by distillation or zone melting. Naturally, tellurium is extracted from different ores in different ways.
Tellurium is harmful
Tellurium is used more and more widely and, therefore, the number of people working with it is increasing. In the first part of the story about element No. 52, we already mentioned the toxicity of tellurium and its compounds. Let's talk about this in more detail - precisely because more and more people have to work with tellurium. Here is a quote from a dissertation on tellurium as an industrial poison: white rats injected with an aerosol of tellurium "became restless, sneezed, rubbed their faces, became lethargic and sleepy." Tellurium acts in a similar way on people.
And myself tellurium and its compounds can bring misfortunes of different "calibers". For example, they cause baldness, affect the composition of the blood, and can block various enzyme systems. Symptoms of chronic poisoning with elemental tellurium - nausea, drowsiness, emaciation; exhaled air acquires a nasty garlic smell of alkyl tellurides.
In acute poisoning with tellurium, serum with glucose is administered intravenously. and sometimes even morphine. As a prophylactic, ascorbic acid is used. But the main prevention is reliable sealing of apparatuses, automation of processes in which tellurium and its compounds are involved.
Element number 52 brings many benefits and therefore deserves attention. But working with him requires caution, clarity and, again, focused attention.
TELLURIUM APPEARANCE. Crystalline tellurium is most similar to antimony. Its color is silvery white. Crystals are hexagonal, the atoms in them form helical chains and are connected by covalent bonds with their nearest neighbors. Therefore, elemental tellurium can be considered an inorganic polymer. Crystalline tellurium is characterized by a metallic luster, although in terms of the complex of chemical properties it can rather be attributed to non-metals. Tellurium is brittle and fairly easy to powder. The question of the existence of an amorphous modification of tellurium has not been unambiguously resolved. When tellurium is reduced from telluric or telluric acids, a precipitate precipitates, but it is still not clear whether these particles are truly amorphous or just very small crystals.
BICOLOR ANHYDRIDE. As it should be for the analogue of sulfur, tellurium exhibits valencies 2-, 4+ and 6+ and much less often 2+. Tellurium monoxide TeO can exist only in gaseous form and is easily oxidized to Te0 2 . It is a white non-hygroscopic, quite stable crystalline substance, melting without decomposition at 733°C; it has a polymer structure.
Tellurium dioxide almost does not dissolve in water - only one part of Te0 2 per 1.5 million parts of water passes into the solution and a solution of weak tellurous acid H 2 Te0 3 of negligible concentration is formed. The acidic properties of telluric acid are also weakly expressed.
H 6 TeO 6 . This formula (and not H 2 TeO 4) was assigned to it after salts of the composition Ag 6 Te0 6 and Hg 3 Te0 6 were obtained, which dissolve well in water. TeOz anhydride, which forms telluric acid, practically does not dissolve in water. This substance exists in two modifications - yellow and gray: α-TeOz and β-TeOz. Gray telluric anhydride is very stable: even when heated, it is not affected by "acids and concentrated alkalis. It is purified from the yellow variety by boiling the mixture in concentrated caustic potash.
SECOND EXCEPTION. When creating the periodic table, Mendeleev placed tellurium and its neighboring iodine (as well as argon and potassium) in groups VI and VII not in accordance with, but in spite of their atomic weights. Indeed, the atomic mass of tellurium is 127.61, and that of iodine is 126.91. This means that iodine would have to stand not behind tellurium, but ahead of it. Mendeleev, however, did not doubt the right
the correctness of his reasoning, since he believed that the atomic weights of these elements were not determined accurately enough. A close friend of Mendeleev, the Czech chemist Boguslav Brauner carefully checked the atomic weights of tellurium and iodine, but his data coincided with the previous ones. The legitimacy of exceptions confirming the rule was established only when the basis of the periodic system was not atomic weights, but nuclear charges, when the isotopic composition of both elements became known. Tellurium, unlike iodine, is dominated by heavy isotopes.
By the way, about isotons. Now 22 isotopes of element No. 52 are known. Eight of them - with mass numbers 120, 122, 123, 124, 125, 126, 128 and 130 - are stable. The last two isotopes are the most common: 31.79 and 34.48%, respectively.
TELLURIUM MINERALS. Although there is significantly less tellurium on Earth than selenium, more minerals of element #52 are known than those of its counterpart. According to their composition, tellurium minerals are twofold: either tellurides, or telluride oxidation products in the earth's crust. Calaverite AuTe 2 and krennerite (Au, Ag) Te2, which are among the few natural gold compounds, are among the first. Natural tellurides of bismuth, lead, and mercury are also known. Native tellurium is very rare in nature. Even before the discovery of this element, it was sometimes found in sulfide ores, but could not be correctly identified. Tellurium minerals have no practical value - all industrial tellurium is a by-product of processing ores of other metals.
For the period 05.12.16 - 24.07..2%. Tellurium price dynamics for the last 3 months is shown in the chart:
62.00 | |||||||||||||||||
38.00 | |||||||||||||||||
05.12.16 | 19.12.16 | 26.01.17 | 11.03.17 | 27.03.17 | 26.04.17 | 30.05.17 | 24.07.17 |
Tellurium: Dynamics of price changes in the world market |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Tellurium is a silvery-white brittle substance with a characteristic metallic sheen. At the same time, a thin layer of tellurium in the light has a red-brown hue, and the vapor has a golden yellow color. Because tellurium is inert, quartz or graphite is used as container materials when it is smelted. Tellurium is a rare element, and a significant demand for it determines its high cost.
In the production of tellurium, waste from the electrolytic refining of lead and copper is mainly used. After roasting the sludge, tellurium precipitates in the cinder, after which it is washed in hydrochloric acid. The resulting hydrochloric acid solution is isolated by passing through sulfur dioxide. For further purification from sulfur, selenium and other impurities, tellurium is dissolved in an alkaline medium, where, under the action of aluminum or zinc, it turns into disodium ditelluride. After it is passed through oxygen or air, and to obtain high purity tellurium, it is chlorinated, followed by purification by distillation, hydrolyzed with water and reduced with hydrogen.
The main producers of tellurium in the CIS are:
OJSC Almalyk Mining and Metallurgical Plant (Uzbekistan);
- OAO Ural Mining and Metallurgical Company (Russian Federation);
- CJSC "Kyshtymsky copper electrolytic plant" (Russian Federation).
Tellurium is used in the production of special lead, which has increased strength and ductility. This property is widely used in the production of wires and other cable products. The combination of tellurium and lead reduces the dissolution of lead under the influence of sulfuric acid by a factor of 10. This property is used in lead-acid batteries.
In special chemical equipment, tellurium glasses are used, which have exceptional transparency, electrical conductivity and fusibility. Some types of tellurium-doped glasses are semiconductors. They are widely used in electronics. And special glasses, with tellurium dioxide, doped with rare earth metals, are used in optical quantum generators as active bodies.
Tellurium alloys are used to create a reflective deformable layer of CDs. Tellurium vapor is used for fluorescent lamps. The light emitted by such lamps has a spectrum comparable to natural sunlight.
Tellurium(lat. tellurium), te, a chemical element of the vi group of the main subgroup of the periodic system of Mendeleev; atomic number 52, atomic mass 127.60, rare scattered elements. It occurs in nature in the form of eight stable isotopes with mass numbers 120, 122-126, 128, 130, of which 128 te (31.79%) and 130 te (34.48%) are the most common. Of the artificially obtained radioactive isotopes, 127 te (T 1/2 = 105 day) and 129 te (T 1/2 = 33,5 day) . T. open F. Muller in 1782. The German scientist M. G. Klaproth confirmed this discovery and gave the element the name "tellurium" (from the Latin tellus, genitive telluris - Earth). The first systematic studies of the chemistry of T. were carried out in the 1930's. 19th century AND I. Berzelius.
Distribution in nature . T. is one of the rarest elements; average content in the earth's crust (clarke) ~1 ? 10 -7% by weight. T. is dispersed in the magma and biosphere; from some hot underground sources it precipitates together with s, ag, au, pb, and other elements. Known hydrothermal deposits of au and non-ferrous metals, enriched with T.; about 40 minerals of this element are associated with them (the most important are altaite, tellurobismuthite, etc.). natural tellurides) . A characteristic admixture of mercury is found in pyrite and other sulfides. T. is extracted from polymetallic ores.
Physical and chemical properties. T. is silvery-white in color with a metallic sheen, brittle, becomes plastic when heated. Crystallizes in the hexagonal system: but= 4.4570 A; from= 5.9290 A; density 6.25 G/ cm 3 at 20°C; t pl 450°C; t kip 990 ± 1.0 °С; specific heat capacity at 20 °C 0.204 kJ/(kg? TO); thermal conductivity at 20 °C 5.999 Tue/(m? TO) ; temperature coefficient of linear expansion 1.68? 10 -5 (20°C). T. diamagnetic, specific magnetic susceptibility at 18 ° C - 0.31? 10 -6 . Brinell hardness 184.3 MN/m 2 (18,43 kgf/mm 2) . Atomic radius 1.7 A, ionic radii: Te 2- 2.22 A, te 4+ 0.89 A, te 6+ 0.56 A.
T. is a semiconductor. Band gap 0.34 ev. Under ordinary conditions and up to the melting point, pure t. has a conductivity R-type. With a decrease in temperature in the range (-100 ° C) - (-80 ° C), a transition occurs: the conductivity of T. becomes n-type. the temperature of this transition depends on the purity of the sample, and it is lower, the purer the sample.
The configuration of the outer electron shell of the atom te 5 s2 5 p 4 . In compounds, it exhibits oxidation states -2; +4; +6, rarely +2. T. - chemical analogue sulfur And Selene with more pronounced metallic properties. With oxygen, T. forms teo oxide, teo 2 dioxide, and teo 3 trioxide. teo exists above 1000 °C in the gas phase. teo 2 is obtained by burning te in air, has amphoteric properties, is difficult to dissolve in water, but is easily soluble in acidic and alkaline solutions. teo 3 is unstable, can only be obtained by decomposition of telluric acid. When heated, T. interacts with hydrogen to form hydrogen telluride h 2 te, a colorless poisonous gas with a sharp, unpleasant odor. Reacts easily with halogens; it is characterized by halides of the type tex 2 and tex 4 (where X-cl and Br); also received tef 4 , tef 6 ; they are all highly volatile and are hydrolyzed by water. T. interacts directly with non-metals (s, P), as well as with metals; it reacts at room temperature with concentrated nitric and sulfuric acids, in the latter case teso 3 is formed, which oxidizes when heated to teoso 4 . Relatively weak acids te are known: hydro-telluric (h 2 te solution in water), telluric h 2 teo 3 and telluric h 6 teo 6; their salts (respectively tellurides, tellurites and tellurates) are slightly or completely insoluble in water (with the exception of alkali metal and ammonium salts). Some organic derivatives of T. are known, for example, rteh, dialkyltellurides r 2 te - low-boiling liquids with an unpleasant odor.
Receipt. T. is extracted along the way during the processing of sulfide ores from semi-products of copper, lead-zinc production, as well as from some gold ores. The main source of raw materials for the production of t. are copper electrolysis sludge containing from 0.5 to 2% te, as well as ag, au, se, cu, and other elements. The sludge is first freed from cu, se, the residue containing noble metals, te, pb, sb and other components is melted down to obtain an alloy of gold and silver. T. in the form of na 2 teo 3 passes into soda-tellurium slags, where its content reaches 20-35%. The slag is crushed, ground and leached with water. T. is deposited from a solution by electrolysis at the cathode. The resulting tellurium concentrate is treated with alkali in the presence of aluminum powder, converting the tellurium into solution in the form of tellurides. The solution is separated from the insoluble residue, concentrating the impurities of heavy metals, and blown with air. At the same time, T. (purity 99%) is deposited in the elemental state. T. of high purity is obtained by repeating telluride processing. The purest T. is obtained by a combination of methods of chemical purification, distillation, and zone melting.
Application. T. is used in semiconductor technology ; as an alloying additive - in lead alloys, cast iron and steel to improve their machinability and increase mechanical characteristics; bi 2 te 3 and sb 2 te 3 are used in thermogenerators, and cdte - in solar panels and as a semiconductor laser materials. T. is also used for bleaching cast iron, vulcanizing latex mixtures, and producing brown and red glasses and enamels.
T. N. Graver.
Tellurium in the body . T. is constantly present in the tissues of plants and animals. In plants growing on soils rich in T., its concentration reaches 2? 10 -4 -2.5? 10 -3%, in terrestrial animals - about 2? 10 -6%. In humans, the daily intake of T. with food and water is about 0.6 mg. It is excreted from the body mainly with urine (over 80%), as well as with feces. Moderately toxic to plants and highly toxic to mammals (causes growth retardation, hair loss, paralysis, etc.).
Occupational poisoning of T. is possible during its smelting and other production operations. Chills, headache, weakness, rapid pulse, lack of appetite, metallic taste in the mouth, garlic smell of exhaled air, nausea, dark coloration of the tongue, irritation of the respiratory tract, sweating, hair loss are observed. Prevention: compliance with the requirements of occupational health, measures for individual protection of the skin, medical examinations of workers.
Lit.: Kudryavtsev A, A. Chemistry and technology of selenium and tellurium, 2nd ed., M.. 1968; Fundamentals of metallurgy, vol. 4, ch. viii, M.. 1967; Filyand M.A.. Semenova E.I. Properties of rare elements, 2nd ed., M.. 1964; Buketov E. A., Malyshev V. P. Extraction of selenium and tellurium from copper electrolyte slimes, A.-A.. 1969; Bowen h. i. M.. trace elements in biochemistry, l.-n. y.. 1966.
Tellurium is a non-metal that has a metallic luster. Its color is silvery white. This element is very rare and diffuse. 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 deposits of gold 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 diamagnet and at 18 °C the value of the specific magnetic susceptibility is -0.31.10-6.
Tellurium is a p-type semiconductor when the ambient conditions are normal or when the material is heated to a boil. When a non-metal is cooled, at a transition of about -100 ° C, it changes its properties and acquires n-type conductivity. The band gap 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 production. Tellurium is also alloyed with copper and steel. This improves their mechanical processing.
Tellurium is also used in glass production. Glass, due to such an impurity, acquires a brown color, and its refractive index increases. In the rubber industry, tellurium is used to carry out the rubber vulcanization process.
Significant demand for tellurium is facilitated by its semiconductor properties. It is considered both a typical and technologically advanced 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 because of 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, not a pure non-metal is used in industry, 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
TELLURIUM[te], -a; m.[from lat. tellus (telluris) - earth] A chemical element (Te), a brittle silver-gray crystalline metal (used in the manufacture of brown dyes, semiconductor materials).
◁ Tellurium, th, th.
tellurium(lat. Tellurium), a chemical element of group VI of the periodic system. Named from lat. tellus, genus. n. telluris - Earth. Silver-gray, very brittle crystals with a metallic sheen, density 6.25 g/cm3, t pl 450°C; semiconductor. It is stable in air, burns at high temperatures with the formation of TeO 2 dioxide. It occurs in nature as tellurides and as native tellurium; often accompanies sulfur and selenium; produced from copper electrolysis waste. Component of alloys (copper, lead, cast iron); dye for glass and ceramics (brown color). Many tellurium compounds are semiconductor materials, infrared radiation receivers.
TELLURIUMTELLURIUM (lat. Tellurium from the 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. It is located in the VIA group, in the 5th period of the Periodic Table of the Elements. chalcogen (cm. CHALCOGENES),
non-metal. Outer electron layer configuration 5 s 2
p 4
. Oxidation states: -2, +2, +4, +6 (valencies II, IV and VI). Electronegativity according to Pauling (cm. PAULING Linus) 2,10.
Tellurium is a brittle, silvery-white substance with a metallic sheen.
Discovery history
It was first discovered in 1782 in the gold-bearing ores of Transylvania by the mining inspector F. I. Muller, who mistook it for a new metal. In 1798 M. G. Klaproth (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 are altaite PbTe, sylvanite AgAuTe 4, calaverite AuTe 2, tetradymite Bi 2 Te 2 S. There are oxygen compounds of tellurium, for example TeO 2 - tellurium ocher. There is native tellurium and, together with selenium (cm. SELENIUM) and gray (cm. SULFUR)(Japanese telluric sulfur contains 0.17% Te and 0.06% Se).
An important source of tellurium is copper and lead ores.
Receipt
The main source is copper electrolytic refining sludge (cm. COPPER) and lead. (cm. LEAD) The sludge is roasted, the tellurium remains in the cinder, which is washed with hydrochloric acid. From the resulting hydrochloric acid solution, tellurium is isolated by passing sulfur dioxide gas SO 2 through it.
Sulfuric acid is added to separate selenium and tellurium. In this case, tellurium dioxide TeO 2 precipitates, and selenious acid remains in solution.
To isolate Te from sludge, they are sintered with soda followed by leaching. Te passes into an alkaline solution, from which, upon neutralization, it precipitates in the form of TeO 2:
Na 2 TeO 3 + 2HC \u003d TeO 2 Ї + 2NaCl.
Tellurium is reduced from oxide TeO 2 with coal.
To purify tellurium from S and Se, its ability, under the action of a reducing agent (Al) in an alkaline medium, to pass into soluble disodium ditelluride Na 2 Te 2 is used:
6Te + 2Al + 8NaOH \u003d 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 \u003d 4Te + 4NaOH.
To obtain tellurium of high purity, it is chlorinated:
Te + 2Cl 2 \u003d TeCl 4.
The resulting tetrachloride is purified by distillation or rectification. The tetrachloride is then hydrolyzed with water:
TeCl 4 + 2H 2 O \u003d TeO 2 Ї + 4HCl,
and the resulting TeO 2 is reduced with hydrogen:
TeO 2 + 4H 2 \u003d Te + 2H 2 O.
Physical and chemical properties
Tallur is a brittle, silvery-white substance with a metallic sheen. The crystal lattice is hexagonal, a=0.44566 nm, c=0.59268 nm. The structure consists of parallel helical chains. Density 6.247 g/cm3. Melting point 449.8°C, boiling point 990°C. Red-brown in thin layers, golden yellow in pairs.
p-type semiconductor. The band gap is 0.32 eV. The electrical conductivity increases with illumination.
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 structure of the b-Sn (Te-II) type is formed. At 6.3 GPa, a Te-III modification with a rhombohedral structure was obtained. Te-II and Te-III exhibit the properties of metals.
It is stable in air at room temperature even in a finely dispersed state. When heated in air, it burns with a bluish-green flame to form TeO 2 dioxide. Standard half-reaction potential:
TeO 3 2– + 3H 2 O + 4e \u003d Te + 6OH -: 0.56V.
At 100–160°C it is oxidized by water:
Te + 2H 2 O \u003d TeO 2 + 2H 2
When boiled in alkaline solutions, tellurium disproportionates with the formation of telluride and tellurite:
8Te + 6KOH \u003d 2K 2 Te + K 2 TeO 3 + 3H 2 O.
Te does not interact with hydrochloric and dilute sulfuric acids. Concentrated H 2 SO 4 dissolves Te, the resulting Te 4 2+ cations color the solution red. Dilute HNO 3 oxidizes Te to tellurous acid H 2 TeO 3:
3Te + 4HNO 3 + H 2 O \u003d 3H 2 TeO 3 + 4NO.
Strong oxidizing agents (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 fluorine) forms tetrahalides. Fluorine oxidizes Te to TeF6 hexafluoride.
Hydrogen telluride H 2 Te - a colorless toxic gas with an unpleasant odor is formed during the 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 increase their mechanical and chemical resistance. Those and its compounds are used in the production of catalysts, special glasses, insecticides, and herbicides.
Physiological action
Tellurium and its volatile compounds are toxic. Ingestion causes nausea, bronchitis, pneumonia. MPC in air 0.01 mg/m3, in water 0.01 mg/l. In case of poisoning, tellurium is excreted from the body in the form of disgustingly smelling organotellurium compounds.
Microamounts of Te are always found in living organisms; its biological role has not been elucidated.
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 in properties to sulfur, 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, to needle-like. Sp. owls. by prism. Ag.: fine-grained and columnar. Tin white. Bl. metal Tv. 2 2.5. Oud. in. 6.3. In hydrotherm. veins with native Au, tellurides Au and Ag, sulfides. Geological ... ... Geological Encyclopedia
- (lat. Tellurium) Te, a 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 brittle crystals with a metallic sheen, 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, occupies the 52nd place in the periodic system. Homolog of sulfur and selenium (VІ group). At. weight 127.5. T. amorphous black powder or brittle pieces of silver-white color, with a metallic sheen; beats weight 6.24, t°… … Big Medical Encyclopedia
- (Tellurium), Te, a chemical element of group VI of the periodic system, atomic number 52, atomic mass 127.60; refers to chalcogens; non-metal. Selected by the Hungarian scientist F. Müller von Reichenstein in 1782 ... Modern Encyclopedia
- (symbol Te), a silvery-white chemical element, discovered in 1782. It occurs in nature 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 lat. tellus earth) (chem.). A chemical element, a silvery-white crystalline substance. Explanatory Dictionary of Ushakov. D.N. Ushakov. 1935 1940 ... Explanatory Dictionary of Ushakov