Carbon (Latin carboneum), C, chemical element IV group periodic system Mendeleev atomic number 6, atomic mass 12,011. Two stable isotop are known: 12 C (98.892%) and 13 C (1.108%). Of radioactive isotopes 14 C is most important with a half-life (T \u003d 5.6? 10 3 years). Small amounts 14 C (about 2? 10-10% by weight) are constantly forming in the upper layers of the atmosphere under the action of cosmic radiation neutrons on a nitrogen isotope 14 n. By specific activity Isotope 14 C in balance of biogenic origin determine their age. 14 C is widely used as .

Historical reference . W. is known with deep antiquity. Charcoal served to restore metals from ores, diamond - like gemstone. Graphite for the manufacture of crucibles and pencils began to be used much later.

In 1778 K. Shelele, Heated graphite with Selutyrah, discovered that, as well as when heating coal with saltort, carbon dioxide is distinguished. Chemical composition Diamond was established as a result of experiments A. Lavoisier (1772) to study the burning of diamond in air and research S. Tennant (1797), which has proven that the same amounts of diamond and coal are given in oxidation equal amounts of carbon dioxide. W. was recognized as a chemical element in 1789 lavanise. Latin name Carboneum W. received from Carbo - coal.

Distribution in nature. The average content of U. in earth Kore 2.3? 10 -2% by weight (1? 10 -2 in ultrasound, 1? 10 -2 - in the main, 2? 10 -2 - on average, 3? 10 -2 - in acidic rocks). W. accumulates in the upper part of the earth's crust (biosphere): in a living substance 18% of US, the wood is 50%, a stone corner of 80%, oil 85%, anthracite 96%. A significant part of W. Lithosphere is concentrated in limestone and dolomites.

The number of own minerals U. - 112; An exceptionally large number of organic compounds of U. - hydrocarbons and their derivatives.

With the accumulation of W. In the earth's crust is associated with the accumulation and many others. Elements sorbed by organic matter and precipitating in the form of insoluble carbonates, etc. A large geochemical role in the earth's crust is played by CO 2 and coal acid. Great amount CO 2 stands out at a volcanicism - in the history of the Earth, it was the main source of W. for the biosphere.

Compared to an average content in the earth's crust, humanity in extremely large quantities extracts W. from subsoil (coal, oil, natural gas), since these fossils are the main source of energy.

A huge geochemical value has a cycle of U.

W. Widespread also in space; In the sun, it ranks 4th after hydrogen, helium and oxygen.

Physics I. chemical properties. Four crystalline modifications are known: graphite, diamond, carbines and lansdalet. Graphite is gray-black, opaque, fat to the touch, scaly, very soft mass with a metal glitter. Built from crystals of a hexagonal structure: A \u003d 2.462 A, C \u003d 6.701 A. At room temperature and normal pressure (0.1 MN / m 2, or 1. kgf / cm 2) graphite is thermodynamically stable. Diamond is very solid, crystalline. Crystals have a cubic grazenarized lattice: a \u003d. 3,560 a. For room temperature and normal pressure, diamond metastable (for details about the structure and properties of diamond and graphite, see the relevant articles). A noticeable conversion of diamond into graphite is observed at temperatures above 1400 ° C in vacuo or in an inert atmosphere. At atmospheric pressure and temperature of about 3700 ° C graphite is derived. Liquid u. Can be obtained at pressures above 10.5 MN / m 2(105 kgf / cm 2) and temperatures above 3700 ° C. For solid u. ( coke, soot, charcoal) It is also characteristic of a state with an unordered structure - the so-called "amorphous" u., which does not represent an independent modification; The basis of its structure is the structure of small-crystalline graphite. Heating some varieties of "amorphous" W. Above 1500-1600 ° C without air access causes them to transform into graphite. The physical properties of the "amorphous" u. Very strongly depend on the dispersion of particles and the presence of impurities. Density, heat capacity, thermal conductivity and electrical conductivity of "amorphous" W. is always higher than graphite. Karbin is artificially obtained. It is a small crystalline black powder (1.9-2 density g / cm 3) . Built from long chains of atoms with, laid parallel to each other. Lonsdaleit found in meteorites and obtained artificially; Its structure and properties are finally installed.

Configuration of the outer electronic shell atom of the U. 2s 2 2p 2. For W. Characteristic education four Covalent bonds due to the excitation of an external electron shell to state 2 sP 3. Therefore, W. is capable equally to attract and give electrons. Chemical Communication can be carried out by sP 3 -, SP 2 -and sp.-Hybrid orbitals, which correspond to coordination numbers 4, 3 and 2. The number of valence electrons U. and the number of valence orbital elements is equally; This is one of the reasons for the sustainability of the connection between atoms.

The unique ability of U. atoms to connect to each other with the formation of durable and long chains and cycles led to the emergence of a huge number of various compounds of U., studied organic chemistry.

In compounds, W. shows the degrees of oxidation -4; +2; +4. Atomic radius 0.77 A, covalent radii 0.77 A, 0.67 A, 0.60 A, respectively, in single, double and triple bonds; ion radius c 4- 2.60 A, C 4+ 0.20 a. Under normal conditions, U. is chemically inert, at high temperatures it connects with many elements, showing strong rehabilitation properties. Chemical activity decreases in a row: "amorphous", u., graphite, diamond; The interaction with air oxygen (combustion) occurs, respectively, at temperatures above 300-500 ° C, 600-700 ° C and 850-1000 ° C with the formation of carbon dioxide CO 2 and carbon monoxide CO.

cO 2 dissolves in water to form coalic acid. In 1906 O. Dils.removed W. C 3 O 2. All forms of U. are resistant to alkalis and acids and are slowly oxidized only by very strong oxidizing agents (chromium mixture, a mixture of concentrated HNO 3 and KCLO 3, etc.). "Amorphous" W. reacts with fluorine at room temperature, graphite and diamond - when heated. Direct compound W. With chlorine occurs in an electric arc; with bromine and iodom u. does not react, so numerous carbon halides Synthesized indirect way. From the oxygaloids of the general formula Cox 2 (where x - halogen) is the most well-known COCL 2 ( phosgene) . Hydrogen with diamond does not interact; With graphite and "amorphous" W. Reacts at high temperatures in the presence of catalysts (Ni, Pt): at 600-1000 ° C, it is formed mainly methane CH 4, at 1500- 2000 ° C - acetylene C 2 H 2 , Dr. hydrocarbons may also be present in the products, such as ethane C 2 H 6 , Benzole C 6 H 6. The interaction of sulfur with "amorphous" and graphite begins at 700-800 ° C, with a diamond at 900-1000 ° C; In all cases, CS 2 serougo harvester is formed. Dr. Compounds U., containing sulfur (CS tyooca, cyanide C 3 S 2, COS and thiophosgene CSCl 2) are obtained by indirect way. When CS 2 interacts with metals sulphides, thiocarbonates are formed - salts of weak thyggolic acid. The interaction of U. with nitrogen to obtain cyan (CN) 2 occurs when the electrical discharge is passed between the coal electrodes in the nitrogen atmosphere. Among nitrogen-containing compounds, W. Important practical value HCN cyanices and its numerous derivatives: cyanides, halo-gentzians, nitriles, etc. at temperatures above 1000 ° C. U. interacts with many metals, giving carbides. All forms of U. When heated, the oxides of metals are restored to form free metals (Zn, CD, CU, PB, etc.) or carbides (CAC 2, MO 2 C, WO, TAC, etc.). W. Reacts at temperatures above 600- 800 ° C with water vapor and carbon dioxide . A distinctive feature of graphite is the ability at moderate heating to 300-400 ° C to interact with alkaline metals and halides to form inclusion connections Type C 8 ME, C 24 ME, C 8 x (where x - halogen, ME - metal). Known compounds of inclusion of graphite with HNO 3, H 2 SO 4, FECL 3, etc. (for example, graphite bisulfate C 24 SO 4 H 2). All forms of U. are insoluble in conventional inorganic and organic solvents, but dissolve in some molten metals (for example, Fe, Ni, CO).

The national economic significance of W. is determined by the fact that over 90% of all the primary sources of energy consumed in the world fall on the organic fuel, The dominant role of which will continue for the coming decades, despite the intensive development nuclear power. Only about 10% of the produced fuel is used as a raw material for basic organic synthesis and petrochemical synthesis, for getting plastic masses and etc.

B. A. Popovkin.

W. In the body . U. is the most important biogenic element that makes up the basis of life on Earth, a structural unit of a huge number of organic compounds involved in building organisms and ensuring their livelihoods ( biopolymers As well as numerous low molecular weight biologically active substances - vitamins, hormones, mediators, etc.). A significant part of the necessary energy organisms is formed in cells due to the oxidation of W. The emergence of life on Earth is considered in modern science as a complex process of evolution of carbon compounds .

The unique role of W. In the wildlife is due to its properties, which, in the aggregation, no other element of the periodic system is posted. Between the atoms of U., as well as between U. and other elements, strong chemical bonds are formed, which, however, can be broken in relatively soft physiological conditions (these bonds can be single, double and triple). Ability to form 4 equivalent valence communications with other atoms of U. Creates the ability to build carbon skeletons of various types - linear, branched, cyclic. It is significant that only three elements are C, O and H - amount to 98% of the total mass of living organisms. This achieves a certain economy in wildlife: with a practically limitless structural variety of carbon compounds, a small number of types chemical ties Allows you to significantly reduce the number of enzymes necessary for splitting and synthesizing organic substances. The features of the structure of the U. atom underlie different species isomeria organic compounds (the ability to optical isomerism turned out to be decisive in the biochemical evolution of amino acids, carbohydrates and some alkaloids).

According to the generally accepted hypothesis, A. I. Oparin, The first organic compounds on Earth had abiogenic origins. Sources of W. served methane (CH 4) and hydrogen cyanide (HCN) contained in primary atmosphere Earth. With the emergence of life the only source of inorganic W., due to which everything is formed organic Biospheres, is carbon dioxide(CO 2), which is in the atmosphere, as well as dissolved in natural waters in the form of HCO - 3. The most powerful mechanism of assimilation (assimilation) U. (in the form of CO 2) - photosynthesis - It is carried out throughout the green plants (about 100 billion is assimilated annually. t. CO 2). On Earth, there is an evolutionary more ancient way to assimilate CO 2 by chemosynthesis; In this case, chemosynthetic microorganisms use not the radiant energy of the Sun, and the energy of oxidation of inorganic compounds. Most animals consume u. With food in the form of ready-made organic compounds. Depending on the method of absorption of organic compounds, it is customary to distinguish autotrophic organisms and heterotrophic organisms. Application for protein biosynthesis and other nutrients of microorganisms that use as the only source of W. hydrocarbons Oil, is one of the important modern scientific and technical problems.

The maintenance of W. In living organisms, in the calculation of the dry matter is: 34.5-40% of water plants and animals, 45.4-46.5% in land plants and animals and 54% of bacteria. In the process of livelihoods of organisms, mainly due to tissue breathing There is an oxidizing decay of organic compounds with the release into the outer medium CO 2. W. Also highlighted as part of more complex finite metabolic products. After the death of animals and plants, part of U. again turns into CO 2 as a result of rotation processes carried out by microorganisms. Thus, there is a cycle of W. In nature . A significant part of W. Mineralizes and forms deposits of the fossil W.: stone coals, oil, limestone, etc. In addition to the main functions - the source of U.-CO 2, dissolved in natural waters and in biological fluids, is involved in maintaining the acidity of the medium optimal for the vital processes. As part of CACO 3 U. forms the outer skeleton of many invertebrates (for example, molluscs), and also contained in corals, eggshell of birds, etc. Such compounds of W., like HCN, CO, CCL 4, which prevail in the primary atmosphere of the Earth the period, in the future, in the process of biological evolution, turned into strong antimetabolites metabolism.

In addition to stable isotopes, O., in nature, the radioactive 14 C is spread (in the human body it contains about 0.1 iCCURI) . Using Isotopes W. In biological and medical research, many major achievements are connected in the study of metabolism and cycle of U. in nature . So, using a radiocarbon tag, the possibility of fixing H 14 CO - 3 plants and tissues of animals was proved, the sequence of photosynthesis reactions was established, the exchange of amino acids were studied, the biosynthesis paths were traced many biologically active compounds, etc. Application 14 C contributed to success molecular biology In the study of protein and transmission biosynthesis mechanisms hereditary information. The determination of the specific activity of 14 C in carbon-containing organic residues allows you to judge their age, which is used in paleontology and archeology.

N. N. Chernov.

LIT: Shafranovsky I. I., Diamonds, M. - L., 1964; Ubbelyod A. R., Lewis F. A., Graphite and its crystal compounds, per. from English, M., 1965; Remy, course of inorganic chemistry, per. with him., Vol. 1, M., 1972; Perelman A. I., geochemistry of elements in the zone of hypergenesis, M., 1972; Nekrasov B.V., Fundamentals of general chemistry, 3 ed., M., 1973; Akhmetov N. S., inorganic chemistry, 2 ed., M., 1975; Vernadsky V. I., Essays of geochemistry, 6 ed., M., 1954; Roginsky S. Z., Schnol S. E., Isotopes in Biochemistry, M., 1963; Biochemistry horizons, lane. from English, M., 1964; Problems of evolutionary and technical biochemistry, M., 1964; Calvin M., Chemical Evolution, Per. from English, M., 1971; Leo A., Siciewits F., Structure and Functions of the cell, lane. from English, 1971, ch. 7; Biosphere, per. from English, M., 1972.

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Carbon dioxide, carbon monoxide, carbon dioxide - all of these names of a substance known to us like carbon dioxide. So what properties this gas has, and what are the areas of its use?

Carbon dioxide and its physical properties

Carbon dioxide consists of carbon and oxygen. Carbon dioxide formula looks like this - CO₂. In nature, it is formed when burning or rotting organic substances. In the air and mineral sources, the gas content is also large enough. In addition, people and animals also distinguish carbon dioxide when exhaled.

Fig. 1. Carbon dioxide molecule.

Carbon dioxide is absolutely colorless gas, it is impossible to see it. He also does not have the smell. However, at its large concentration, a person can develop hypercupnia, that is, suffocation. The lack of carbon dioxide can also cause health problems. As a result of the lack, this gas can develop the opposite state to suffocation - hinders.

If you put carbon dioxide in the conditions of low temperature, then at -72 degrees it crystallizes and becomes like snow. Therefore, carbon dioxide in solid state is called "dry snow".

Fig. 2. Dry snow - carbon dioxide.

Carbon dioxide is 1.5 times tight. Its density is 1.98 kg / m³ Chemical bond in the carbon dioxide molecule covalent polar. Polar it is due to the fact that oxygen is larger than the value of electronegability.

An important concept when studying substances is molecular and molar mass. The molar mass of carbon dioxide is 44. This number is formed from the sum of the relative atomic masses of atoms that are part of the molecule. The values \u200b\u200bof the relative atomic masses are taken from the Table D.I. Mendeleev and are rounded up to integer numbers. Accordingly, the molar mass of CO₂ \u003d 12 + 2 * 16.

In order to calculate the mass fractions of the elements in carbon dioxide, it is necessary to follow the formulate of the mass fractions of each chemical element in the substance.

n. - the number of atoms or molecules.
A. r. - relative atomic weight of the chemical element.
Mr. - relative molecular weight of the substance.
Calculate the relative molecular weight of carbon dioxide.

Mr (CO₂) \u003d 14 + 16 * 2 \u003d 44 W (C) \u003d 1 * 12/44 \u003d 0.27 or 27% Since two oxygen atoms are included in the carbon dioxide formula, then n \u003d 2 w (o) \u003d 2 * 16/44 \u003d 0.73 or 73%

Answer: W (C) \u003d 0.27 or 27%; W (O) \u003d 0.73 or 73%

Chemical and biological properties of carbon dioxide

Carbon dioxide has acidic properties, as it is acidic oxide, and when dissolved in water forms coalic acid:

CO₂ + H₂O \u003d H₂CO₃

It reacts with alkalis, resulting in carbonates and bicarbonates. This gas is not susceptible to burning. It burns only some active metals, such as magnesium.

When heated carbon dioxide disintegrates on carbon monoxide and oxygen:

2Co₃ \u003d 2Co + O₃.

Like others acid oxidesThis gas easily reacts with other oxides:

SAO + CO₃ \u003d CACO₃.

Carbon dioxide is part of all organic matter. The cycle of this gas in nature is carried out with the help of producers, consumers and reasons. In the course of vital activity, a person produces about 1 kg of carbon dioxide per day. When inhaling, we get oxygen, however, at this moment carbon dioxide is formed in the alveols. At this moment there is an exchange: oxygen falls into the blood, and carbon dioxide comes out.

The preparation of carbon dioxide occurs during the production of alcohol. Also, this gas is a bypass product upon receipt of nitrogen, oxygen and argon. The use of carbon dioxide is necessary in food Industrywhere carbon dioxide acts as a preservative, as well as carbon dioxide in the form of a liquid is contained in fire extinguishers.

Fig. 3. Fire extinguisher.

What did we know?

Carbon dioxide is a substance that in normal conditions has no color and smell. In addition to its usual name - carbon dioxide, it is also called carbon oxide or carbon dioxide.

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Carbon C is in the periodic table of Mendeleev at number 6. More primitive people noticed that after burning wood, coal is formed, which can be drawn on the walls of the cave. As part of any organic compounds there are carbon. The most studied two allotropic carbon modifications: graphite and diamond.

Carbon in organic chemistry

Carbon takes a special place in the periodic system. Due to its structure, it forms long chains of linear or cyclic structure. There are more than 10 million organic compounds. Despite its diversity, in air and under the action of temperature, they will always turn into carbon dioxide and.

The role of carbon in our daily life is enormous. Without carbon dioxide, photosynthesis will not occur - one of the main biological processes.

Using carbon

Carbon is widely used in medicine to create various organic nature medicines. Carbon isotopes allow radiocarbon analysis. Without carbon, the work of the metallurgical industry is impossible. Coal burning in solid fuel pyrolysis boilers serves as a source of energy. In the oil refining industry, gasoline and diesel fuel are produced from organic compounds of carbon. To a large extent, carbon is necessary for the production of sugar. It is also used in the synthesis of organic compounds, important for all spheres of everyday life.

Carbon (Latin carboneum), C, chemical element IV group of periodic Mendeleev system, atomic number 6, atomic weight 12,011. Two stable isotop are known: 12 C (98.892%) and 13 C (1.108%). 14 C with a half-life (T EQ F (1; 2) \u003d 5.6 × 10 3 years) is most important from radioactive isotopes. Small amounts 14 C (about 2 × 10 -10% by weight) are constantly forming in the upper layers of the atmosphere under the action of cosmic radiation neutrons on a nitrogen isotope 14 N. According to the specific activity of the isotope 14 C in biogenic origin, their age is determined. 14 C is widely used as isotopic indicator.

Historical reference. W. is known with deep antiquity. Charcoal served to restore metals from ores, diamond - like a gem. Graphite for the manufacture of crucibles and pencils began to be used much later.

In 1778 K. SheleleHeated graphite with Selutyrah, discovered that, as well as when heated coal with an associate, carbon dioxide is distinguished. The chemical composition of the diamond was established as a result of experiments A. Lavoisier (1772) to study the burning of diamond in air and research S. Tennant (1797), which has proven that the same amounts of diamond and coal are given in oxidation equal amounts of carbon dioxide. W. was recognized as a chemical element in 1789 lavanise. Latin name Carboneum W. received from Carbo - coal.

Distribution in nature. The average content of U. in the earth's crust of 2.3 × 10 -2% by weight (1 × 10 -2 in ultrasound, 1 × 10 -2 - in the main, 2 × 10 -2 - in the middle, 3 × 10 -2 - in acidic rocks). W. accumulates in the upper part of the earth's crust (biosphere): in a living substance 18% of US, the wood is 50%, a stone corner of 80%, oil 85%, anthracite 96%. A significant part of W. Lithosphere is concentrated in limestone and dolomites.

The number of own minerals U. - 112; An exceptionally large number of organic compounds of U. - hydrocarbons and their derivatives.

With the accumulation of W. In the earth's crust is associated with the accumulation and many others. Elements sorbed by organic matter and precipitating in the form of insoluble carbonates, etc. A large geochemical role in the earth's crust is played by CO 2 and coal acid. A huge amount of CO 2 stands out at a volcanism - in the history of the Earth, it was the main source of U. for the biosphere.

Compared to an average content in the earth's crust, humanity in extremely large quantities extracts W. from subsoil (coal, oil, natural gas), since these fossils are the main source of energy.

A huge geochemical value has a cycle of U. (see below the carbon section in the body and Art. Createness of substances).

W. Widespread also in space; In the sun, it ranks 4th after hydrogen, helium and oxygen.

Physics and chemical properties. Four crystalline modifications are known: graphite, diamond, carbines and lansdalet. Graphite is gray-black, opaque, fat to the touch, scaly, very soft mass with a metal glitter. Built from crystals of a hexagonal structure: A \u003d 2.462Å, C \u003d 6.701Å. At room temperature and normal pressure (0.1 MN / m 2, or 1. kgf / cm 2) Graphite is thermodynamically stable. Diamond is very solid, crystalline. Crystals have a cubic grazenarized lattice: a \u003d. 3,560 Å. For room temperature and normal pressure, diamond metastable (for details about the structure and properties of diamond and graphite, see the relevant articles). A noticeable transformation of diamond into graphite is observed at temperatures above 1400 ° C in vacuo or in an inert atmosphere. At atmospheric pressure and temperature about 3700 ° C, graphite is removed. Liquid u. Can be obtained at pressures above 10.5 MN / m 2(105 kgf / cm 2) and temperatures above 3700 ° C. For solid u. ( coke, soot, charcoal) It is also characterized by a state with an unordered structure - the so-called "amorphous" U., which does not represent an independent modification; The basis of its structure is the structure of small-crystalline graphite. Heating some varieties of "amorphous" W. Above 1500-1600 ° C without air access causes them to transformation into graphite. The physical properties of "amorphous" W. Very strongly depend on the dispersion of particles and the presence of impurities. Density, heat capacity, thermal conductivity and electrical conductivity of "amorphous" W. is always higher than graphite. Karbin is artificially obtained. It is a small crystalline black powder (density of 1.9-2 g / cm 3). Built from long chains of atoms with, laid parallel to each other. Lonsdaleit found in meteorites and obtained artificially; Its structure and properties are finally installed.

Configuration of the outer electronic shell atom of the U. 2s 2 2p 2. For W. Characterized by the formation of four covalent bonds due to the excitation of the external electron shell to state 2 sP 3. Therefore, W. is capable equally to attract and give electrons. Chemical Communication can be carried out by sP 3 -, SP 2 -and sp.-Hybrid orbitals, which correspond to coordination numbers 4, 3 and 2. The number of valence electrons U. and the number of valence orbital elements is equally; This is one of the reasons for the sustainability of the connection between atoms.

The unique ability of U. atoms to connect to each other with the formation of durable and long chains and cycles led to the emergence of a huge number of various compounds of U., studied organic chemistry.

In compounds, W. shows the degrees of oxidation -4; +2; +4. Atomic radius of 0.77Å, covalent radii 0.77Å, 0.67Å, 0.60Å, respectively, in single, double and triple bonds; ion radius C 4- 2.60Å, C 4+ 0.20Å. Under normal conditions, U. is chemically inert, at high temperatures it connects with many elements, showing strong rehabilitation properties. Chemical activity decreases in a row: "amorphous" u., graphite, diamond; The interaction with air oxygen (combustion) occurs, respectively, at temperatures above 300-500 ° C, 600-700 ° C and 850-1000 ° C with the formation of CO 2 carbon dioxide and CO carbon oxide.

CO 2 dissolves in water to form coalic acid. In 1906 O. Dils. Removed W. C 3 O 2. All forms of U. are resistant to alkalis and acids and are slowly oxidized only by very strong oxidizing agents (chromium mixture, a mixture of concentrated HNO 3 and KCLO 3, etc.). "Amorphous" W. reacts with fluorine at room temperature, graphite and diamond - when heated. Direct compound W. With chlorine occurs in an electric arc; with bromine and iodom u. does not react, so numerous carbon halides Synthesized indirect way. From the oxygaloids of the general formula Cox 2 (where x - halogen) is the most well-known COCL 2 ( phosgene). Hydrogen with diamond does not interact; With graphite and amorphous, U. reacts at high temperatures in the presence of catalysts (Ni, Pt): at 600-1000 ° C, it is formed mainly methane CH 4, at 1500- 2000 ° C - acetylene C 2 H 2 , Dr. hydrocarbons may also be present in the products, such as ethane C 2 H 6 , Benzole C 6 H 6. The interaction of sulfur with "amorphous" and graphite begins at 700-800 ° C, with a diamond at 900-1000 ° C; In all cases, CS 2 serougo harvester is formed. Dr. Compounds U., containing sulfur (CS tyooca, cyanide C 3 S 2, COS and thiophosgene CSCl 2) are obtained by indirect way. When CS 2 interacts with metals sulphides, thiocarbonates are formed - salts of weak thyggolic acid. The interaction of U. with nitrogen to obtain cyan (CN) 2 occurs when the electrical discharge is passed between the coal electrodes in the nitrogen atmosphere. Among nitrogen-containing compounds of W. An important practical value is HCN cyanice (see Hydrocyanic acid) and its numerous derivatives: cyanides, halo-gentials, nitriles, etc. at temperatures above 1000 ° C. U. interacts with many metals, giving carbide. All forms of U. When heated, the oxides of metals are restored to form free metals (Zn, CD, CU, PB, etc.) or carbides (CAC 2, MO 2 C, WO, TAC, etc.). W. reacts at temperatures above 600- 800 ° C with water vapor and carbon dioxide (see Fuel gasification). A distinctive feature of graphite is the ability of moderate heating to 300-400 ° C to interact with alkaline metals and halides to form inclusion connections Type C 8 ME, C 24 ME, C 8 x (where x - halogen, ME - metal). Known compounds of inclusion of graphite with HNO 3, H 2 SO 4, FECL 3, etc. (for example, graphite bisulfate C 24 SO 4 H 2). All forms of U. are insoluble in conventional inorganic and organic solvents, but dissolve in some molten metals (for example, Fe, Ni, CO).

The national economic significance of W. is determined by the fact that over 90% of all the primary sources of energy consumed in the world fall on the organic fuelThe dominant role of which will continue for the coming decades, despite the intensive development of nuclear energy. Only about 10% of the produced fuel is used as a raw material for basic organic synthesis and petrochemical synthesis, for getting plastic masses and etc.

For receipt and use of W. and its compounds, see also Diamond, Graphite, Coke, Soot, Carbon refractories, Carbon dioxide, Carbon oxide, Carbonates.

B. A. Popovkin.

W. In the body. U. is the most important biogenic element that makes up the basis of life on Earth, a structural unit of a huge number of organic compounds involved in building organisms and ensuring their livelihoods ( biopolymers, as well as numerous low molecular weight biologically active substances - vitamins, hormones, mediators, etc.). A significant part of the necessary energy organisms is formed in cells due to the oxidation of W. The emergence of life on Earth is considered in modern science as a complex process of the evolution of carbon compounds (see The origin of life).

The unique role of W. In the wildlife is due to its properties, which, in the aggregation, no other element of the periodic system is posted. Between the atoms of U., as well as between U. and other elements, strong chemical bonds are formed, which, however, can be broken in relatively soft physiological conditions (these bonds can be single, double and triple). Ability to form 4 equivalent valence communications with other atoms of U. Creates the ability to build carbon skeletons of various types - linear, branched, cyclic. It is significant that only three elements are C, O and H - amount to 98% of the total mass of living organisms. This achieves a certain economy in wildlife: with a practically limitless structural variety of carbon compounds, a small number of types of chemical bonds makes it much reduced by the number of enzymes needed for splitting and synthesizing organic matter. Features of the structure of the U. atom underlie the basis of various species isomeria organic compounds (the ability to optical isomerism turned out to be decisive in the biochemical evolution of amino acids, carbohydrates and some alkaloids).

According to the generally accepted hypothesis, A. I. OparinThe first organic compounds on Earth had abiogenic origins. Sources of W. served methane (CH 4) and cyanide hydrogen (HCN) contained in the primary atmosphere of the Earth. With the emergence of life the only source of inorganic W., due to which the whole organic matter of the biosphere is formed, is carbon dioxide (CO 2), which is in the atmosphere, as well as dissolved in natural waters in the form of HCO - 3. The most powerful mechanism of assimilation (assimilation) U. (in the form of CO 2) - photosynthesis - It is carried out throughout the green plants (about 100 billion tons of CO 2 is assimilated annually. On Earth, there is an evolutionary more ancient way to assimilate CO 2 by chemosynthesis; In this case, chemosynthetic microorganisms use not the radiant energy of the Sun, and the energy of oxidation of inorganic compounds. Most animals consume u. With food in the form of ready-made organic compounds. Depending on the method of absorption of organic compounds, it is customary to distinguish autotrophic organisms and heterotrophic organisms. Application for protein biosynthesis and other nutrients of microorganisms that use as the only source of W. hydrocarbons Oil, is one of the important modern scientific and technical problems.

The content of W. in living organisms in the calculation of the dry matter is: 34.5-40% in aqueous plants and animals, 45.4-46.5% in land plants and animals and 54% from bacteria. In the process of livelihoods of organisms, mainly due to fabric breathing, there is an oxidizing decay of organic compounds with the release of CO 2 into the external environment. W. Also highlighted as part of more complex finite metabolic products. After the death of animals and plants, part of U. again turns into CO 2 as a result of rotation processes carried out by microorganisms. Thus, the cycle of W. In nature (see Createness of substances). Significant part of W. Mineralizes and forms the deposits of the fossil in the fossil: stone coals, oil, limestone, etc. In addition to the main functions - the source of U.-CO 2, dissolved in natural waters and in biological fluids, is involved in maintaining the optimal environmental acidity processes . As part of CACO 3 U. forms the outer skeleton of many invertebrates (for example, molluscs), and also contained in corals, eggshell of birds, etc. Such compounds of W., like HCN, CO, CCL 4, which prevail in the primary atmosphere of the Earth the period, in the future, in the process of biological evolution, turned into strong antimetabolites metabolism.

In addition to stable isotopes, W., in nature, the radioactive 14 C (in the human body it contains about 0.1 μCuri). Using Isotopes W. In biological and medical studies, many large achievements in the study of metabolism and cycle of W. are related in nature (see Isotopic indicators). So, using a radiocarbon tag, the possibility of fixing H 14 CO - 3 plants and tissues of animals was proved, the sequence of photosynthesis reactions was established, the exchange of amino acids were studied, the biosynthesis paths were traced many biologically active compounds, etc. Application 14 C contributed to the successes of molecular biology in the study of protein biosynthesis mechanisms and the transfer of hereditary information. The determination of the specific activity of 14 C in carbon-containing organic residues allows you to judge their age, which is used in paleontology and archeology.

N. N. Chernov.

LIT: Shafranovsky I. I., Diamonds, M. - L., 1964; Ubbelyod A. R., Lewis F. A., Graphite and its crystal compounds, per. from English, M., 1965; Remy, course of inorganic chemistry, per. with him., Vol. 1, M., 1972; Perelman A. I., geochemistry of elements in the zone of hypergenesis, M., 1972; Nekrasov B.V., Fundamentals of general chemistry, 3 ed., M., 1973; Akhmetov N. S., inorganic chemistry, 2 ed., M., 1975; Vernadsky V. I., Essays of geochemistry, 6 ed., M., 1954; Roginsky S. Z., Schnol S. E., Isotopes in Biochemistry, M., 1963; Biochemistry horizons, lane. from English, M., 1964; Problems of evolutionary and technical biochemistry, M., 1964; Calvin M., Chemical Evolution, Per. from English, M., 1971; Leo A., Siciewits F., Structure and Functions of the cell, lane. from English, 1971, ch. 7; Biosphere, per. from English, M., 1972.

Oxygen is in the second period of the VI of the main group of the outdated short variant of the periodic table. According to new numbering standards, this is the 16th group. The corresponding decision was made by the Jewaya in 1988. Oxygen formula as a simple substance - O 2. Consider its basic properties, role in nature and farm. Let's start with the characteristics of the entire group that the oxygen heads. The element differs from the Hallcogenes related to it, and water is different from hydrogen selenium and tellurium. An explanation of all distinguishing features can be found only by learning about the structure and properties of the atom.

Hallcohes - related oxygen elements

Atoms similar by properties form one group in the periodic system. Oxygen is headed by a family of chalcogens, but differs from them for a number of properties.

The atomic mass of oxygen - the group's generator is 16 a. e. m. Halcogens When the compounds with hydrogen and metals are formed, there is its usual oxidation degree: -2. For example, in the composition of water (H 2 O), the oxidative number of oxygen is -2.

The composition of typical hydrogen hydrogen compounds corresponds to the general formula: H 2 R. In the dissolution of these substances, acids are formed. Only the hydrogen compound of oxygen - water - has special properties. According to the conclusions of scientists, this unusual substance is both very weak acid, and a very weak basis.

Sera, Selenium and Tellur have typical positive degrees of oxidation (+4, +6) in compounds with oxygen and other non-metals with high electronegitability (EO). The composition of chalcogen oxides reflect general formulas: RO 2, RO 3. The corresponding acids are composition: H 2 RO 3, H 2 RO 4.

Elements correspond to simple substances: oxygen, sulfur, selenium, tellurium and polonium. The first three representatives show non-metallic properties. Oxygen formula - O 2. Allotropic modification of the same element - ozone (about 3). Both modifications are gases. Sulfur and selenium - solid nonmetals. Tellur - metalloid substance, conductor electric current, polonium - metal.

Oxygen - the most common element

We already know that there is another variety of existence of the same chemical element in the form of a simple substance. This ozone is a gas that is formed at an altitude of about 30 km from the surface of the Earth layer, often called the ozone screen. Related oxygen enters into water molecules, the composition of many rocks and minerals, organic compounds.

The structure of an oxygen atom

Periodic table of Mendeleev contains full information About oxygen:

1. The sequence number of the element is 8.
2. The charge of the nucleus - +8.
3. The total number of electrons is 8.
4. Electronic oxygen formula - 1S 2 2S 2 2P 4.

In nature there are three stable isotop, which have the same serial number in the Mendeleev table, identical composition of protons and electrons, but miscellaneous number neutrons. Isotoves are indicated by the same symbol - O. For comparison, we present a diagram reflecting the composition of three oxygen isotopes:

Oxygen properties - chemical element

On the 2r pioneer of the atom there are two unpaired electronthat explains the appearance of oxidation degrees -2 and +2. Two paired electrons cannot disconnect so that the degree of oxidation has increased to +4, like sulfur and other chalcogenes. The reason is the lack of a free sublevel. Therefore, in compounds, the chemical element oxygen does not exhibit valence and the degree of oxidation equal to the number of the group in a short variant of the periodic system (6). The usual oxidative number for it is -2.

Only in compounds with fluorine oxygen shown uncharacteristic positive degree of oxidation +2. The value of EO two strong non-metals is different: EO (O) \u003d 3.5; EO (F) \u003d 4. As a more electronegative chemical element, the fluorine kept its electrons stronger and attracts valence particles on an oxygen atom. Therefore, in reaction with fluorine, oxygen is a reducing agent, electron gives electrons.

Oxygen - a simple substance

English researcher D. Priestley in 1774 during the experiments allocated gas in the decomposition of mercury oxide. Two years earlier, the same substance in its pure form received K. Shelele. Only a few years later, the French chemist A. Lavoisier found that the gas is part of the air, studied the properties. Chemical formula Oxygen - O 2. Reflect in the composition of the composition of the substance electrons involved in the formation of non-polar covalent Communication - About :: about. We will replace each binding electronic pair of one feature: O \u003d O. Such an oxygen formula clearly shows that atoms in the molecule are connected between the two common pairs of electrons.

We will perform simple calculations and determine what is equal to the relative molecular weight of oxygen: Mr (O 2) \u003d Ar (O) x 2 \u003d 16 x 2 \u003d 32. For comparison: Mr (Rev.) \u003d 29. Chemical oxygen formula is different from one Oxygen atom. So Mr (O 3) \u003d Ar (O) x 3 \u003d 48. Ozone is 1.5 times heavier than oxygen.

Physical properties

Oxygen is gas without color, taste and odor (at a conventional temperature and pressure equal to atmospheric). Substance is a little heavier air; dissolved in water, but in small quantities. The oxygen melting point is a negative value of -218.3 ° C. The point in which the liquid oxygen turns into the gas again - it is its boiling point. For molecules about 2 physical quantity Reaching -182,96 ° C. In a liquid and solid state, oxygen purchases light blue color.

Getting oxygen in the laboratory

When heating oxygen-containing substances, such as potassium permanganate, a colorless gas is distinguished, which can be collected in the flask or test tube. If you make a burning lady into pure oxygen, then it burns more brightly than in the air. Two other laboratory methods for producing oxygen - decomposition of hydrogen peroxide and potassium chlorate (beverage salt). Consider a diagram of the device that is used for thermal decomposition.

It is necessary to pour out a bit of the bertolen salt into the test tube or a round bottom flask, close the cork with the gas feed tube. Its opposite end should be directed (under water) to the tilting up the bottom of the flask. The neck should be lowered into a wide glass or a crystallizer filled with water. When heating the test tube with the beverage salt, oxygen is released. According to the gas feed tube, he enters the flask, displacing water out of it. When the flask is filled with gas, it is closed under water with a plug and turn over. Oxygen obtained in this laboratory experiment can be used to study the chemical properties of a simple substance.

Combustion

If burning of substances in oxygen is performed in the laboratory, then you need to know and comply with fireproof rules. Hydrogen instantly burns in the air, and mixed with oxygen in a 2: 1 ratio, it is explosive. The combustion of substances in pure oxygen occurs much more intense than in the air. This phenomenon explains the composition of the air. Oxygen in the atmosphere is slightly more than 1/5 of the part (21%). The burning is the reaction of substances with oxygen, as a result of which different products are formed, mainly oxides of metals and non-metals. Fire hazardous mixtures of o 2 with combustible substances, moreover, the resulting compounds can be toxic.

The combustion of ordinary candle (or matches) is accompanied by carbon dioxide formation. The following experience can be carried out at home. If the substance is burned under a glass can or a large glass, then burning will stop as soon as all oxygen is spent. Nitrogen does not support breathing and burning. Carbon dioxide - oxidation product - no longer react with oxygen. Transparent allows you to detect the presence after burning the candle. If we skip combustion products through calcium hydroxide, then the solution is muttered. A chemical reaction occurs between lime water and carbon dioxide, it turns out insoluble calcium carbonate.

Operating oxygen on an industrial scale

The cheapest process, as a result of which the air-free molecules are obtained, is not related to the conduct of chemical reactions. In industry, let's say, at metallurgical combines, air at low temperature and high pressure liquefit. Such essential components of the atmosphere as nitrogen and oxygen are boiled at different temperatures. Separate air mixture with gradual heating to normal temperature. First, nitrogen molecules are distinguished, then oxygen. The separation method is based on different physical properties of simple substances. The formula of a simple substance of oxygen is the same as it was before cooling and air liquefaction - o 2.

As a result of some electrolysis reactions, oxygen is also distinguished, it is collected above the corresponding electrode. Gas is needed by industrial, construction enterprises in large volumes. Oxygen needs are constantly growing, especially needs a chemical industry. Store the obtained gas for production and medical purposes in steel cylinders equipped with labeling. Oxygen containers are painted in blue or blue to distinguish from other liquefied gases - nitrogen, methane, ammonia.

Chemical calculations according to the formula and equations of reactions involving molecules O 2

The numerical value of the molar mass of oxygen coincides with the other value - relative molecular weight. Only in the first case there are units of measurement. The short formula of the substance of oxygen and its molar mass must be recorded as follows: M (O 2) \u003d 32 g / mol. Under normal conditions, pouring any gas corresponds to a volume of 22.4 liters. So, 1 mol about 2 is 22.4 liters of substances, 2 moses of 2 - 44.8 liters. According to the reaction equation between oxygen and hydrogen, it can be noted that 2 poles of hydrogen and 1 mole of oxygen interact:

If 1 mol of hydrogen is involved in the reaction, then the volume of oxygen will be 0.5 mol. 22.4 l / mol \u003d 11.2 liters.

The role of molecules about 2 in the nature and life of a person

Oxygen is consumed by alive organisms on earth and participates in the cycle of substances over 3 billion years. This is the main substance for breathing and metabolism, with its help there is a decomposition of nutrients molecules, the energy required for organisms is synthesized. Oxygen is constantly spent on Earth, but its reserves are replenished thanks to photosynthesis. Russian scientist K. Timiryazev believed that thanks to this process, there is still life on our planet.

The role of oxygen in nature and the economy is great:

• absorbed in the process of breathing with living organisms;
• participates in photosynthesis reactions in plants;
• enters the composition of organic molecules;
• the processes of rotting, fermentation, rust flows with the participation of oxygen acting as an oxidizing agent;
• used to obtain valuable organic synthesis products.

Liquefied oxygen in cylinders are used for cutting and welding metals at high temperatures. These processes are carried out on machine-building factories, transport and construction enterprises. For work under water, underground, at high altitude in airless space, people also need molecules about 2. Used in medicine to enrich air composition inhaled by patients. Gas for medical purposes is different from the technical practically complete absence of extraneous impurities, smell.

Oxygen - perfect oxidizer

Known oxygen compounds with all chemical elements Tables of Mendeleev, except for the first representatives of the family of noble gases. Many substances directly enter the reaction with atoms about, excluding halogens, gold and platinum. Great importance have phenomena with the participation of oxygen, which are accompanied by the release of light and heat. Such processes are widely used in everyday life, industry. In metallurgy, the interaction of ores with oxygen is called firing. Pre-grinding ore is mixed with oxygen-enriched air. At high temperatures, the restoration of metals from sulphides to simple substances occurs. So get iron and some non-ferrous metals. The presence of pure oxygen increases the speed of technological processes in different sectors of chemistry, technology and metallurgy.

The appearance of a cheap method for producing oxygen from the air by separating the components at low temperatures was stimulated by the development of many areas of industrial production. Chemists consider molecules about 2 and atoms about ideal oxidative agents. These are natural materials, they are constantly renewed in nature, do not pollute environment. Moreover, chemical reactions With the participation of oxygen, most often completed by the synthesis of another natural and safe product - water. The role of 2 in the neutralization of toxic production waste, water purification from pollution. In addition to oxygen, its allotropic modification is used for disinfection - ozone. This simple substance has high oxidative activity. In ozonation of water, pollutants decompose. Ozone is also destructive effect on the pathogenic microflora.