Carbon

CARBON-A; m. Chemical element (C), the most important component of all organic substances in nature. Carbon atoms. Carbon content percentage. Without carbon, life is impossible.

◁ Carbon, oh, oh. Y atoms. Carbon, oh, oh. Containing carbon. Uh steel.

carbon

(lat. Carboneum), chemical element of group IV of the periodic table. The main crystal modifications are diamond and graphite. Under normal conditions, carbon is chemically inert; At high temperatures it combines with many elements (strong reducing agent). The carbon content in the earth's crust is 6.5 10 16 tons. A significant amount of carbon (about 10 13 tons) is included in the composition of fossil fuels (coal, natural gas, oil, etc.), as well as in the composition of atmospheric carbon dioxide (6 10 11 t) and hydrosphere (10 14 t). The main carbon-containing minerals are carbonates. Carbon has the unique ability to form a huge number of compounds, which can consist of an almost unlimited number of carbon atoms. The variety of carbon compounds determined the emergence of one of the main branches of chemistry - organic chemistry. Carbon is a biogenic element; its compounds play a special role in the life of plant and animal organisms (average carbon content - 18%). Carbon is widespread in space; on the Sun it ranks 4th after hydrogen, helium and oxygen.

CARBON

CARBON (Latin Carboneum, from carbo - coal), C (read “ce”), a chemical element with atomic number 6, atomic weight 12.011. Natural carbon consists of two stable nuclides: 12 C, 98.892% by mass and 13 C - 1.108%. In the natural mixture of nuclides, the radioactive nuclide 14 C (b - emitter, half-life 5730 years) is always present in negligible quantities. It is constantly formed in the lower layers of the atmosphere under the action of neutrons from cosmic radiation on the nitrogen isotope 14 N:
14 7 N + 1 0 n = 14 6 C + 1 1 H.
Carbon is located in group IVA, in the second period of the periodic table. Configuration of the outer electron layer of an atom in ground state 2 s 2 p 2 . The most important oxidation states are +2 +4, –4, valences IV and II.
The radius of a neutral carbon atom is 0.077 nm. The radius of the C 4+ ion is 0.029 nm (coordination number 4), 0.030 nm (coordination number 6). The sequential ionization energies of a neutral atom are 11.260, 24.382, 47.883, 64.492 and 392.09 eV. Electronegativity according to Pauling (cm. PAULING Linus) 2,5.
Historical reference
Carbon has been known since ancient times. Charcoal was used to recover metals from ores, diamond (cm. DIAMOND (mineral))- like a precious stone. In 1789, the French chemist A. L. Lavoisier (cm. LAVOISIER Antoine Laurent) concluded about the elemental nature of carbon.
Synthetic diamonds were first obtained in 1953 by Swedish researchers, but they did not manage to publish the results. In December 1954, artificial diamonds were obtained, and at the beginning of 1955, employees of the General Electric company published the results. (cm. GENERAL ELECTRIC)
In the USSR, artificial diamonds were first obtained in 1960 by a group of scientists led by V. N. Bakul and L. F. Vereshchagin (cm. VERESHCHAGIN Leonid Fedorovich) .
In 1961, a group of Soviet chemists under the leadership of V.V. Korshak synthesized a linear modification of carbon - carbyne. Soon after, carbine was discovered in the Ries meteorite crater (Germany). In 1969, in the USSR, whisker-like diamond crystals were synthesized at ordinary pressure, possessing high strength and practically free of defects.
In 1985, Croteau (cm. CUTE Harold) discovered a new form of carbon - fullerenes (cm. FULLERENES) C 60 and C 70 in the mass spectrum of graphite evaporated during laser irradiation. At high pressures, lonsdaleite was obtained.
Being in nature
Content in the earth's crust is 0.48% by weight. Accumulates in the biosphere: in living matter 18% coal, in wood 50%, peat 62%, natural combustible gases 75%, oil shale 78%, hard and brown coal 80%, oil 85%, anthracite 96%. A significant part of the coal of the lithosphere is concentrated in limestones and dolomites. Carbon in the +4 oxidation state is part of carbonate rocks and minerals (chalk, limestone, marble, dolomite). Carbon dioxide CO 2 (0.046% by weight) is a permanent component of atmospheric air. Carbon dioxide is always present in dissolved form in the water of rivers, lakes and seas.
Substances containing carbon have been discovered in the atmosphere of stars, planets and meteorites.
Receipt
Since ancient times, coal has been produced by incomplete combustion of wood. In the 19th century, charcoal was replaced by bituminous coal (coke) in metallurgy.
Currently, cracking is used for the industrial production of pure carbon. (cm. CRACKING) natural gas methane (cm. METHANE) CH 4:
CH 4 = C + 2H 2
Charcoal for medicinal purposes is prepared by burning coconut shells. For laboratory needs, pure coal that does not contain non-combustible impurities is obtained by incomplete combustion of sugar.
Physical and chemical properties
Carbon is a non-metal.
The variety of carbon compounds is explained by the ability of its atoms to bond with each other, forming three-dimensional structures, layers, chains, and cycles. Four allotropic modifications of carbon are known: diamond, graphite, carbyne and fullerite. Charcoal consists of tiny crystals with a disordered graphite structure. Its density is 1.8-2.1 g/cm3. Soot is highly ground graphite.
Diamond is a mineral with a cubic face-centered lattice. The C atoms in diamond are located in sp 3 -hybridized state. Each atom forms 4 covalent s-bonds with four neighboring C atoms located at the vertices of the tetrahedron, in the center of which is the C atom. The distances between the atoms in the tetrahedron are 0.154 nm. There is no electronic conductivity, the band gap is 5.7 eV. Of all simple substances, diamond has the maximum number of atoms per unit volume. Its density is 3.51 g/cm 3. . Hardness on the Mohs mineralogical scale (cm. MOHS SCALE) taken as 10. A diamond can only be scratched by another diamond; but it is fragile and upon impact breaks into pieces of irregular shape. Thermodynamically stable only at high pressures. However, at 1800 °C the transformation of diamond into graphite occurs quickly. The reverse transformation of graphite into diamond occurs at 2700°C and a pressure of 11-12 GPa.
Graphite is a layered dark gray substance with a hexagonal crystal lattice. Thermodynamically stable over a wide range of temperatures and pressures. Consists of parallel layers formed by regular hexagons of C atoms. The carbon atoms of each layer are located opposite the centers of the hexagons located in adjacent layers; the position of the layers is repeated every other, and each layer is shifted relative to the other in the horizontal direction by 0.1418 nm. Inside the layer, the bonds between atoms are covalent, formed sp 2 -hybrid orbitals. The connections between the layers are carried out by weak van der Waals (cm. INTERMOLECULAR INTERACTION) forces, so graphite is easily exfoliated. This state is stabilized by the fourth delocalized p-bond. Graphite has good electrical conductivity. Graphite density is 2.1-2.5 kg/dm3.
In all allotropic modifications, under normal conditions, carbon is chemically inactive. It enters into chemical reactions only when heated. In this case, the chemical activity of carbon decreases in the series soot-charcoal-graphite-diamond. Soot in air ignites when heated to 300°C, diamond - at 850-1000°C. During combustion, carbon dioxide CO 2 and CO are formed. By heating CO 2 with coal, carbon monoxide (II) CO is also obtained:
CO 2 + C = 2CO
C + H 2 O (superheated steam) = CO + H 2
Carbon monoxide C 2 O 3 was synthesized.
CO 2 is an acidic oxide; it is associated with weak, unstable carbonic acid H 2 CO 3, which exists only in highly dilute cold aqueous solutions. Salts of carbonic acid - carbonates (cm. CARBONATES)(K 2 CO 3, CaCO 3) and bicarbonates (cm. HYDROCARBONATES)(NaHCO 3, Ca(HCO 3) 2).
With hydrogen (cm. HYDROGEN) graphite and charcoal react at temperatures above 1200°C to form a mixture of hydrocarbons. Reacting with fluorine at 900°C, it forms a mixture of fluorocarbon compounds. By passing an electric discharge between carbon electrodes in a nitrogen atmosphere, cyanogen gas (CN) 2 is obtained; If hydrogen is present in the gas mixture, hydrocyanic acid HCN is formed. At very high temperatures, graphite reacts with sulfur, (cm. SULFUR) silicon, boron, forming carbides - CS 2, SiC, B 4 C.
Carbides are produced by the interaction of graphite with metals at high temperatures: sodium carbide Na 2 C 2, calcium carbide CaC 2, magnesium carbide Mg 2 C 3, aluminum carbide Al 4 C 3. These carbides are easily decomposed by water into metal hydroxide and the corresponding hydrocarbon:
Al 4 C 3 + 12H 2 O = 4Al(OH) 3 + 3CH 4
With transition metals, carbon forms metal-like chemically stable carbides, for example, iron carbide (cementite) Fe 3 C, chromium carbide Cr 2 C 3, tungsten carbide WC. Carbides are crystalline substances; the nature of the chemical bond can be different.
When heated, coal reduces many metals from their oxides:
FeO + C = Fe + CO,
2CuO+ C = 2Cu+ CO 2
When heated, it reduces sulfur(VI) to sulfur(IV) from concentrated sulfuric acid:
2H 2 SO 4 + C = CO 2 + 2SO 2 + 2H 2 O
At 3500°C and normal pressure, carbon sublimates.
Application
Over 90% of all primary sources of energy consumed in the world come from fossil fuels. 10% of the extracted fuel is used as raw material for basic organic and petrochemical synthesis to produce plastics.
Physiological action
Carbon is the most important biogenic element; it is a structural unit of organic compounds involved in the construction of organisms and ensuring their vital functions (biopolymers, vitamins, hormones, mediators and others). The carbon content in living organisms on a dry matter basis is 34.5-40% for aquatic plants and animals, 45.4-46.5% for terrestrial plants and animals, and 54% for bacteria. During the life of organisms, oxidative decomposition of organic compounds occurs with the release of CO 2 into the external environment. Carbon dioxide (cm. CARBON DIOXIDE), dissolved in biological fluids and natural waters, participates in maintaining the optimal acidity of the environment for life. Carbon in CaCO 3 forms the exoskeleton of many invertebrates and is found in corals and eggshells.
During various production processes, particles of coal, soot, graphite, and diamond enter the atmosphere and are found in it in the form of aerosols. MPC for carbon dust in work areas is 4.0 mg/m 3, for coal 10 mg/m 3.

encyclopedic Dictionary. 2009 .

Synonyms:

See what “carbon” is in other dictionaries:

Table of nuclides General information Name, symbol Carbon 14, 14C Alternative names radiocarbon, radiocarbon Neutrons 8 Protons 6 Properties of the nuclide Atomic mass ... Wikipedia

Table of nuclides General information Name, symbol Carbon 12, 12C Neutrons 6 Protons 6 Nuclide properties Atomic mass 12.0000000(0) ... Wikipedia

Table of nuclides General information Name, symbol Carbon 13, 13C Neutrons 7 Protons 6 Nuclide properties Atomic mass 13.0033548378(10) ... Wikipedia

- (lat. Carboneum) C, chemical. element of group IV of the Mendeleev periodic system, atomic number 6, atomic mass 12.011. The main crystal modifications are diamond and graphite. Under normal conditions, carbon is chemically inert; at high... ... Big Encyclopedic Dictionary

- (Carboneum), C, chemical element of group IV of the periodic table, atomic number 6, atomic mass 12.011; non-metal. The content in the earth's crust is 2.3×10 2% by mass. The main crystalline forms of carbon are diamond and graphite. Carbon is the main component... ... Modern encyclopedia

Carbon- (Carboneum), C, chemical element of group IV of the periodic table, atomic number 6, atomic mass 12.011; non-metal. The content in the earth's crust is 2.3´10 2% by weight. The main crystalline forms of carbon are diamond and graphite. Carbon is the main component... ... Illustrated Encyclopedic Dictionary

CARBON- (1) chem. element, symbol C (lat. Carboneum), at. And. 6, at. m. 12,011. It exists in several allotropic modifications (forms) (diamond, graphite and rarely carbine, chaoite and lonsdaleite in meteorite craters). Since 1961 / the mass of an atom of the 12C isotope has been adopted ... Big Polytechnic Encyclopedia

- (symbol C), a widespread non-metallic element of the fourth group of the periodic table. Carbon forms a huge number of compounds, which, together with hydrocarbons and other non-metallic substances, form the basis... ... Scientific and technical encyclopedic dictionary

Carbon is perhaps one of the most impressive elements of chemistry on our planet, which has the unique ability to form a huge variety of different organic and inorganic bonds.

In a word, carbon compounds that have unique characteristics are the basis of life on our planet.

What is carbon

In the chemical table D.I. Mendeleev's carbon is number six, belongs to group 14 and is designated “C”.

Physical properties

It is a hydrogen compound belonging to the group of biological molecules, the molar mass and molecular weight of which is 12.011, and the melting point is 3550 degrees.

The oxidation state of a given element can be: +4, +3, +2, +1, 0, -1, -2, -3, -4, and the density is 2.25 g/cm3.

In the aggregate state, carbon is a solid, and the crystal lattice is atomic.

Carbon has the following allotropic modifications:

• graphite;
• fullerene;
• carbine

Atomic structure

An atom of a substance has an electronic configuration of the form - 1S 2 2S 2 2P 2. At the outer level, an atom has 4 electrons located in two different orbitals.

If we take the excited state of the element, then its configuration becomes 1S 2 2S 1 2P 3.

In addition, an atom of a substance can be primary, secondary, tertiary and quaternary.

Chemical properties

Being in normal conditions, the element is inert and interacts with metals and non-metals at elevated temperatures:

• interacts with metals, resulting in the formation of carbides;
• reacts with fluorine (halogen);
• at elevated temperatures interacts with hydrogen and sulfur;
• when the temperature rises, it ensures the reduction of metals and non-metals from oxides;
• at 1000 degrees it interacts with water;
• lights up when the temperature rises.

Carbon production

Carbon can be found in nature in the form of black graphite or, very rarely, in the form of diamond. Unnatural graphite is produced by reacting coke with silica.

Unnatural diamonds are produced by applying heat and pressure along with catalysts. This melts the metal, and the resulting diamond comes out as a precipitate.

Adding nitrogen results in yellowish diamonds, while adding boron produces bluish diamonds.

History of discovery

Carbon has been used by people since ancient times. The Greeks knew graphite and coal, and diamonds were first found in India. By the way, people often took similar-looking compounds as graphite. But even despite this, graphite was widely used for writing, because even the word “grapho” is translated from Greek as “I write.”

Currently, graphite is also used in writing, in particular it can be found in pencils. At the beginning of the 18th century, trade in diamonds began in Brazil, many deposits were discovered, and already in the second half of the 20th century, people learned to obtain unnatural precious stones.

Currently, non-natural diamonds are used in industry, and real diamonds are used in jewelry.

The role of carbon in the human body

Carbon enters the human body along with food, during the day - 300 g. And the total amount of the substance in the human body is 21% of body weight.

This element consists of 2/3 muscles and 1/3 bones. And the gas is removed from the body along with exhaled air or with urea.

It is worth noting: Without this substance, life on Earth is impossible, because carbon forms bonds that help the body fight the destructive influence of the surrounding world.

Thus, the element is capable of forming long chains or rings of atoms, which provide the basis for many other important bonds.

Occurrence of carbon in nature

The element and its compounds can be found everywhere. First of all, we note that the substance makes up 0.032% of the total amount of the earth’s crust.

A single element can be found in coal. And the crystalline element is found in allotropic modifications. Also, the amount of carbon dioxide in the air is constantly increasing.

Large concentrations of the element in the environment can be found as compounds with various elements. For example, carbon dioxide is contained in the air in an amount of 0.03%. Minerals such as limestone or marble contain carbonates.

All living organisms contain compounds of carbon with other elements. In addition, the remains of living organisms become deposits such as oil and bitumen.

Application of carbon

Compounds of this element are widely used in all areas of our lives and the list of them can be endless, so we will indicate a few of them:

• graphite is used in pencil leads and electrodes;
• diamonds are widely used in jewelry and drilling;
• carbon is used as a reducing agent to remove elements such as iron ore and silicon;
• activated carbon, consisting mainly of this element, is widely used in the medical field, industry and everyday life.

DEFINITION

Carbon- the sixth element of the Periodic Table. Designation - C from the Latin “carboneum”. Located in the second period, group IVA. Refers to non-metals. The nuclear charge is 6.

Carbon is found in nature both in a free state and in the form of numerous compounds. Free carbon occurs in the form of diamond and graphite. In addition to fossil coal, there are large accumulations of oil in the depths of the Earth. Carbonic acid salts, especially calcium carbonate, are found in huge quantities in the earth's crust. There is always carbon dioxide in the air. Finally, plant and animal organisms consist of substances in the formation of which carbon takes part. Thus, this element is one of the most common on Earth, although its total content in the earth’s crust is only about 0.1% (wt.).

Atomic and molecular mass of carbon

The relative molecular mass of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and the relative atomic mass of an element (A r) is how many times the average mass of atoms of a chemical element is greater than 1/12 mass of a carbon atom.

Since in the free state carbon exists in the form of monatomic molecules C, the values ​​of its atomic and molecular masses coincide. They are equal to 12.0064.

Allotropy and allotropic modifications of carbon

In the free state, carbon exists in the form of diamond, which crystallizes in the cubic and hexagonal (lonsdaleite) system, and graphite, which belongs to the hexagonal system (Fig. 1). Forms of carbon such as charcoal, coke or soot have a disordered structure. There are also allotropic modifications obtained synthetically - these are carbyne and polycumulene - varieties of carbon built from linear chain polymers of the type -C= C- or = C = C=.

Rice. 1. Allotropic modifications of carbon.

Allotropic modifications of carbon are also known, having the following names: graphene, fullerene, nanotubes, nanofibers, astralen, glassy carbon, colossal nanotubes; amorphous carbon, carbon nanobuds and carbon nanofoam.

Carbon isotopes

In nature, carbon exists in the form of two stable isotopes 12 C (98.98%) and 13 C (1.07%). Their mass numbers are 12 and 13, respectively. The nucleus of an atom of the 12 C carbon isotope contains six protons and six neutrons, and the 13 C isotope contains the same number of protons and five neutrons.

There is one artificial (radioactive) isotope of carbon, 14 C, with a half-life of 5730 years.

Carbon ions

The outer energy level of the carbon atom has four electrons, which are valence electrons:

1s 2 2s 2 2p 2 .

As a result of chemical interaction, carbon can lose its valence electrons, i.e. be their donor, and turn into positively charged ions or accept electrons from another atom, i.e. be their acceptor and turn into negatively charged ions:

C 0 -2e → C 2+ ;

C 0 -4e → C 4+ ;

C 0 +4e → C 4- .

Molecule and carbon atom

In the free state, carbon exists in the form of monatomic molecules C. Here are some properties characterizing the carbon atom and molecule:

Carbon alloys

The most famous carbon alloys around the world are steel and cast iron. Steel is an alloy of iron and carbon, the carbon content of which does not exceed 2%. In cast iron (also an alloy of iron and carbon), the carbon content is higher - from 2 to 4%.

Examples of problem solving

EXAMPLE 1

Exercise	What volume of carbon monoxide (IV) will be released (n.s.) when burning 500 g of limestone containing 0.1 mass fraction of impurities.
Solution	Let us write the reaction equation for limestone firing: CaCO 3 = CaO + CO 2 -. Let's find a mass of pure limestone. To do this, we first determine its mass fraction without impurities: w clear (CaCO 3) = 1 - w impurity = 1 - 0.1 = 0.9. m clear (CaCO 3) = m (CaCO 3) × w clear (CaCO 3); m clear (CaCO 3) = 500 × 0.9 = 450 g. Let's calculate the amount of limestone substance: n(CaCO 3) = m clear (CaCO 3) / M(CaCO 3); n(CaCO 3) = 450 / 100 = 4.5 mol. According to the reaction equation n(CaCO 3) :n(CO 2) = 1:1, it means n(CaCO 3) = n(CO 2) = 4.5 mol. Then, the volume of carbon monoxide (IV) released will be equal to: V(CO 2) = n(CO 2) ×V m; V(CO 2) = 4.5 × 22.4 = 100.8 l.
Answer	100.8 l

EXAMPLE 2

Exercise	How much of a solution containing 0.05 parts by mass, or 5% hydrogen chloride, is required to neutralize 11.2 g of calcium carbonate?
Solution	Let us write the equation for the reaction of neutralization of calcium carbonate with hydrogen chloride: CaCO 3 + 2HCl = CaCl 2 + H 2 O + CO 2 -. Let's find the amount of calcium carbonate: M(CaCO 3) = A r (Ca) + A r (C) + 3×A r (O); M(CaCO 3) = 40 + 12 + 3×16 = 52 + 48 = 100 g/mol. n(CaCO 3) = m (CaCO 3) / M(CaCO 3); n(CaCO 3) = 11.2 / 100 = 0.112 mol. According to the reaction equation n(CaCO 3) :n(HCl) = 1:2, which means n(HCl) = 2 ×n(CaCO 3) = 2 ×0.224 mol. Let us determine the mass of hydrogen chloride contained in the solution: M(HCl) = A r (H) + A r (Cl) = 1 + 35.5 = 36.5 g/mol. m(HCl) = n(HCl) × M(HCl) = 0.224 × 36.5 = 8.176 g. Let's calculate the mass of the hydrogen chloride solution: m solution (HCl) = m(HCl)× 100 / w(HCl); m solution (HCl) = 8.176 × 100 / 5 = 163.52 g.
Answer	163.52 g

(first electron)

Carbon(chemical symbol C) chemical element of the 4th group of the main subgroup of the 2nd period of the Mendeleev periodic system, serial number 6, atomic mass of a natural mixture of isotopes 12.0107 g/mol.

Story

Carbon in the form of charcoal was used in ancient times for smelting metals. Allotropic modifications of carbon—diamond and graphite—have long been known. The elemental nature of carbon was established by A. Lavoisier in the late 1780s.

origin of name

International name: carbō - coal.

Physical properties

Carbon exists in a variety of allotropes with very diverse physical properties. The variety of modifications is due to the ability of carbon to form chemical bonds of different types.

Carbon isotopes

Natural carbon consists of two stable isotopes - 12 C (98.892%) and 13 C (1.108%) and one radioactive isotope 14 C (β-emitter, T ½ = 5730 years), concentrated in the atmosphere and upper part of the earth's crust. It is constantly formed in the lower layers of the stratosphere as a result of the impact of neutrons from cosmic radiation on nitrogen nuclei according to the reaction: 14 N (n, p) 14 C, and also, since the mid-1950s, as a man-made product of nuclear power plants and as a result of testing hydrogen bombs .

The radiocarbon dating method, widely used in Quaternary geology and archeology, is based on the formation and decay of 14 C.

Allotropic modifications of carbon

Schemes of the structure of various modifications of carbon
a: diamond, b: graphite, c: lonsdaleite
d: fullerene—buckyball C 60, e: fullerene C 540, f: fullerene C 70
g: amorphous carbon, h: carbon nanotube

Allotropy of carbon

lonsdaleite

fullerenes

carbon nanotubes

amorphous carbon

Coal carbon black soot

The electron orbitals of a carbon atom can have different geometries, depending on the degree of hybridization of its electron orbitals. There are three basic geometries of the carbon atom.

Tetrahedral - is formed by mixing one s- and three p-electrons (sp 3 hybridization). The carbon atom is located in the center of the tetrahedron, connected by four equivalent σ-bonds to carbon or other atoms at the vertices of the tetrahedron. The carbon allotropic modifications diamond and lonsdaleite correspond to this geometry of the carbon atom. Carbon exhibits such hybridization, for example, in methane and other hydrocarbons.

Trigonal - is formed by mixing one s- and two p-electron orbitals (sp²-hybridization). The carbon atom has three equivalent σ bonds located in the same plane at an angle of 120° to each other. The p-orbital not involved in hybridization, located perpendicular to the plane of σ bonds, is used to form a π bond with other atoms. This carbon geometry is characteristic of graphite, phenol, etc.

Digonal - is formed by mixing one s- and one p-electrons (sp-hybridization). In this case, two electron clouds are elongated along one direction and look like asymmetrical dumbbells. The other two p electrons make a π bond. Carbon with this atomic geometry forms a special allotropic modification - carbyne.

Graphite and diamond

The main and well-studied crystalline modifications of carbon are diamond and graphite. Under normal conditions, only graphite is thermodynamically stable, while diamond and other forms are metastable. At atmospheric pressure and temperatures above 1200 K, Kalmaz begins to transform into graphite; above 2100 K, the transformation occurs in seconds. ΔН 0 transition—1.898 kJ/mol. At normal pressure, carbon sublimates at 3780 K. Liquid carbon exists only at a certain external pressure. Triple points: graphite-liquid-steam T = 4130 K, p = 10.7 MPa. The direct transition of graphite to diamond occurs at 3000 K and a pressure of 11-12 GPa.

At pressures above 60 GPa, the formation of a very dense modification C III (density 15–20% higher than the density of diamond), which has metallic conductivity, is assumed. At high pressures and relatively low temperatures (about 1200 K), a hexagonal modification of carbon with a wurtzite-type crystal lattice—lonsdaleite (a = 0.252 nm, c = 0.412 nm, space group P6 3 /tts), density 3.51 is formed from highly oriented graphite g/cm³, that is, the same as that of diamond. Lonsdaleite is also found in meteorites.

Ultradisperse diamonds (nanodiamonds)

In the 1980s In the USSR, it was discovered that under conditions of dynamic loading of carbon-containing materials, diamond-like structures, called ultrafine diamonds (UDD), can form. Currently, the term “nanodiamonds” is increasingly used. The particle size in such materials is a few nanometers. The conditions for the formation of UDD can be realized during the detonation of explosives with a significant negative oxygen balance, for example, mixtures of TNT with hexogen. Such conditions can also be realized during impacts of celestial bodies on the surface of the Earth in the presence of carbon-containing materials (organic matter, peat, coal, etc.). Thus, in the fall zone of the Tunguska meteorite, UDAs were discovered in the forest floor.

Carbin

The crystalline modification of carbon of the hexagonal system with a chain structure of molecules is called carbyne. The chains have either a polyene structure (—C≡C—) or a polycumulene structure (=C=C=). Several forms of carbyne are known, differing in the number of atoms in the unit cell, cell sizes and density (2.68-3.30 g/cm³). Carbyne occurs in nature in the form of the mineral chaoite (white veins and inclusions in graphite) and is obtained artificially by oxidative dehydropolycondensation of acetylene, the action of laser radiation on graphite, from hydrocarbons or CCl 4 in low-temperature plasma.

Carbyne is a fine-crystalline black powder (density 1.9-2 g/cm³) and has semiconductor properties. Obtained under artificial conditions from long chains of atoms carbon, laid parallel to each other.

Carbyne is a linear polymer of carbon. In the carbyne molecule, the carbon atoms are connected in chains alternately either by triple and single bonds (polyene structure) or permanently by double bonds (polycumulene structure). This substance was first obtained by Soviet chemists V.V. Korshak, A.M. Sladkov, V.I. Kasatochkin and Yu.P. Kudryavtsev in the early 60s. V Institute of Organoelement Compounds of the USSR Academy of Sciences.Carbine has semiconducting properties, and under the influence of light its conductivity increases greatly. The first practical application is based on this property - in photocells.

Fullerenes and carbon nanotubes

Carbon is also known in the form of cluster particles C 60, C 70, C 80, C 90, C 100 and the like (fullerenes), as well as graphenes and nanotubes.

Amorphous carbon

The structure of amorphous carbon is based on the disordered structure of single-crystalline (always contains impurities) graphite. These are coke, brown and black coals, carbon black, soot, activated carbon.

Being in nature

The carbon content in the earth's crust is 0.1% by mass. Free carbon is found in nature in the form of diamond and graphite. The bulk of carbon is in the form of natural carbonates (limestones and dolomites), fossil fuels - anthracite (94-97% C), brown coal (64-80% C), bituminous coal (76-95% C), oil shale (56- 78% C), oil (82-87% C), flammable natural gases (up to 99% methane), peat (53-56% C), as well as bitumen, etc. In the atmosphere and hydrosphere it is found in the form of carbon dioxide CO 2 , in the air there is 0.046% CO 2 by mass, in the waters of rivers, seas and oceans it is ~60 times more. Carbon is included in the composition of plants and animals (~18%).
The human body enters carbon through food (normally about 300 g per day). The total carbon content in the human body reaches about 21% (15 kg per 70 kg body weight). Carbon makes up 2/3 of muscle mass and 1/3 of bone mass. Excreted from the body primarily through exhaled air (carbon dioxide) and urine (urea)
The carbon cycle in nature includes the biological cycle, the release of CO 2 into the atmosphere during the combustion of fossil fuels, from volcanic gases, hot mineral springs, from the surface layers of ocean waters, etc. The biological cycle consists of the fact that carbon in the form of CO 2 is absorbed from the troposphere by plants . Then from the biosphere it returns again to the geosphere: with plants, carbon enters the body of animals and humans, and then, when animal and plant materials rot, into the soil and in the form of CO 2 into the atmosphere.

In a vapor state and in the form of compounds with nitrogen and hydrogen, carbon is found in the atmosphere of the Sun, planets, and is found in stone and iron meteorites.

Most carbon compounds, and above all hydrocarbons, have a pronounced character of covalent compounds. The strength of simple, double and triple bonds of C atoms with each other, the ability to form stable chains and cycles from C atoms determine the existence of a huge number of carbon-containing compounds studied in organic chemistry.

Chemical properties

At ordinary temperatures, carbon is chemically inert; at sufficiently high temperatures it combines with many elements and exhibits strong reducing properties. The chemical activity of different forms of carbon decreases in the following order: amorphous carbon, graphite, diamond; in air they ignite at temperatures respectively above 300–500 °C, 600–700 °C and 850–1000 °C.

Oxidation states +4, −4, rarely +2 (CO, metal carbides), +3 (C2N2, halogenyanides); electron affinity 1.27 eV; The ionization energy during the sequential transition from C 0 to C 4+ is 11.2604, 24.383, 47.871 and 64.19 eV, respectively.

Inorganic compounds

Carbon reacts with many elements to form carbides.

Combustion products are carbon monoxide CO and carbon dioxide CO 2. The unstable oxide C 3 O 2 (melting point −111°C, boiling point 7°C) and some other oxides are also known. Graphite and amorphous carbon begin to react with H 2 at 1200°C, with F 2 at 900°C, respectively.

CO 2 with water forms weak carbonic acid - H 2 CO 3, which forms salts - Carbonates. The most widespread carbonates on Earth are calcium (chalk, marble, calcite, limestone and other minerals) and magnesium (dolomite).

Graphite with halogens, alkali metals and other substances forms inclusion compounds. When an electric discharge is passed between carbon electrodes in an N2 environment, cyanogen is formed; at high temperatures, the interaction of carbon with a mixture of H2 and N2 produces hydrocyanic acid. With sulfur, carbon produces carbon disulfide CS 2, CS and C 3 S 2 are also known. Carbon forms carbides with most metals, boron and silicon. The reaction of carbon with water vapor is important in industry: C + H 2 O = CO + H 2 (Gasification of solid fuels). When heated, carbon reduces metal oxides to metals, which is widely used in metallurgy.

Organic compounds

Due to the ability of carbon to form polymer chains, there is a huge class of carbon-based compounds, which are much larger than inorganic ones, and which are studied in organic chemistry. Among them are the most extensive groups: hydrocarbons, proteins, fats, etc.

Carbon compounds form the basis of terrestrial life, and their properties largely determine the range of conditions in which such life forms can exist. By the number of atoms in living cells, the share of carbon is about 25%, and by mass fraction it is about 18%.

Application

Graphite is used in the pencil industry. It is also used as a lubricant at particularly high or low temperatures.

Diamond, due to its exceptional hardness, is an indispensable abrasive material. The grinding attachments of drills are coated with diamond. In addition, cut diamonds are used as gemstones in jewelry. Due to its rarity, high decorative qualities and a combination of historical circumstances, a diamond is invariably the most expensive gemstone. The exceptionally high thermal conductivity of diamond (up to 2000 W/mK) makes it a promising material for semiconductor technology as substrates for processors. But the relatively high price (about $50/gram) and the difficulty of diamond processing limit its use in this area.
In pharmacology and medicine, various carbon compounds are widely used - derivatives of carbonic acid and carboxylic acids, various heterocycles, polymers and other compounds. Thus, carbolene (activated carbon) is used to absorb and remove various toxins from the body; graphite (in the form of ointments) - for the treatment of skin diseases; radioactive carbon isotopes—for scientific research (radiocarbon dating).

Carbon plays a huge role in human life. Its applications are as varied as this many-sided element itself.

Carbon is the basis of all organic substances. Any living organism consists largely of carbon. Carbon is the basis of life. The source of carbon for living organisms is usually CO 2 from the atmosphere or water. Through photosynthesis, it enters biological food chains in which living things devour each other or each other's remains and thereby obtain carbon to build their own bodies. The biological cycle of carbon ends either by oxidation and return to the atmosphere, or by burial in the form of coal or oil.

Carbon in the form of fossil fuels: coal and hydrocarbons (oil, natural gas) is one of the most important sources of energy for humanity.

Toxic effect

Carbon is part of atmospheric aerosols, as a result of which the regional climate may change and the number of sunny days may decrease. Carbon enters the environment in the form of soot in the exhaust gases of vehicles, during the combustion of coal at thermal power plants, during open-pit mining of coal, underground gasification, production of coal concentrates, etc. The carbon concentration above combustion sources is 100-400 μg/m³, in large cities 2, 4-15.9 µg/m³, rural areas 0.5-0.8 µg/m³. With gas aerosol emissions from nuclear power plants, (6-15).10 9 Bq/day 14 CO 2 enters the atmosphere.

The high carbon content in atmospheric aerosols leads to increased morbidity in the population, especially in the upper respiratory tract and lungs. Occupational diseases—mainly anthracosis and dust bronchitis. In the air of the working area, MPC, mg/m³: diamond 8.0, anthracite and coke 6.0, coal 10.0, carbon black and carbon dust 4.0; in atmospheric air the maximum one-time is 0.15, the average daily is 0.05 mg/m³.

The toxic effect of 14 C, which is included in protein molecules (especially in DNA and RNA), is determined by the radiation effect of beta particles and nitrogen recoil nuclei (14 C (β) → 14 N) and the transmutation effect - a change in the chemical composition of the molecule as a result of the transformation of the C atom per atom N. Permissible concentration of 14 C in the air of the working area DK A 1.3 Bq/l, in the atmospheric air DK B 4.4 Bq/l, in water 3.0.10 4 Bq/l, maximum permissible intake through the respiratory system 3 ,2.10 8 Bq/year.

Additional Information

— Carbon compounds
— Radiocarbon dating
— Orthocarboxylic acid

Allotropic forms of carbon:

Diamond
Graphene
Graphite
Carbin
Lonsdaleite
Carbon nanotubes
Fullerenes

Amorphous forms:

Soot
Carbon black
Coal

Carbon isotopes:

Unstable (less than a day): 8C: Carbon-8, 9C: Carbon-9, 10C: Carbon-10, 11C: Carbon-11
Stable: 12C: Carbon-12, 13C: Carbon-13
10–10,000 years: 14C: Carbon-14
Unstable (less than 24 hours): 15C: Carbon-15, 16C: Carbon-16, 17C: Carbon-17, 18C: Carbon-18, 19C: Carbon-19, 20C: Carbon-20, 21C: Carbon-21, 22C: Carbon-22

Nuclide table

Carbon, Carboneum, C (6)
Carbon (English Carbon, French Carbone, German Kohlenstoff) in the form of coal, soot and soot has been known to mankind since time immemorial; about 100 thousand years ago, when our ancestors mastered fire, they dealt with coal and soot every day. Probably, very early people became acquainted with allotropic modifications of carbon - diamond and graphite, as well as fossil coal. It is not surprising that the combustion of carbon-containing substances was one of the first chemical processes to interest man. Since the burning substance disappeared when consumed by fire, combustion was considered a process of decomposition of the substance, and therefore coal (or carbon) was not considered an element. The element was fire, a phenomenon that accompanies combustion; In ancient teachings about the elements, fire usually appears as one of the elements. At the turn of the XVII - XVIII centuries. The phlogiston theory arose, put forward by Becher and Stahl. This theory recognized the presence in each combustible body of a special elementary substance - a weightless fluid - phlogiston, which evaporates during the combustion process.

When a large amount of coal is burned, only a little ash remains; phlogistics believed that coal is almost pure phlogiston. This is what explained, in particular, the “phlogisticating” effect of coal—its ability to restore metals from “limes” and ores. Later phlogistics, Reaumur, Bergman and others, already began to understand that coal is an elementary substance. However, “clean coal” was first recognized as such by Lavoisier, who studied the process of combustion of coal and other substances in air and oxygen. In the book “Method of Chemical Nomenclature” by Guiton de Morveau, Lavoisier, Berthollet and Fourcroix (1787), the name “carbon” (carbone) appeared instead of the French “pure coal” (charbone pur). Under the same name, carbon appears in the “Table of Simple Bodies” in Lavoisier’s “Elementary Textbook of Chemistry.” In 1791, the English chemist Tennant was the first to obtain free carbon; he passed phosphorus vapor over calcined chalk, resulting in the formation of calcium phosphate and carbon. It has been known for a long time that diamond burns without leaving a residue when heated strongly. Back in 1751, the French king Francis I agreed to give diamond and ruby ​​for combustion experiments, after which these experiments even became fashionable. It turned out that only diamond burns, and ruby ​​(aluminum oxide with an admixture of chromium) can withstand prolonged heating at the focus of the ignition lens without damage. Lavoisier carried out a new experiment on burning diamonds using a large incendiary machine and came to the conclusion that diamond is crystalline carbon. The second allotrope of carbon - graphite in the alchemical period was considered a modified lead luster and was called plumbago; It was only in 1740 that Pott discovered the absence of any lead impurity in graphite. Scheele studied graphite (1779) and, being a phlogistician, considered it a special kind of sulfur body, a special mineral coal containing bound “aerial acid” (CO2) and a large amount of phlogiston.

Twenty years later, Guiton de Morveau turned diamond into graphite and then into carbonic acid by careful heating.

The international name Carboneum comes from the Latin. carbo (coal). This word is of very ancient origin. It is compared with cremare - to burn; root sag, cal, Russian gar, gal, gol, Sanskrit sta means to boil, cook. The word “carbo” is also associated with the names of carbon in other European languages ​​(carbon, charbone, etc.). The German Kohlenstoff comes from Kohle - coal (Old German kolo, Swedish kylla - to heat). Old Russian ugorati, or ugarati (to burn, scorch) has the root gar, or mountains, with a possible transition to gol; coal in Old Russian yugal, or coal, of the same origin. The word diamond (Diamante) comes from the ancient Greek - indestructible, unyielding, hard, and graphite from the Greek - I write.

At the beginning of the 19th century. the old word coal in Russian chemical literature was sometimes replaced by the word “carbonate” (Scherer, 1807; Severgin, 1815); Since 1824, Soloviev introduced the name carbon.

Carbon (C) is the sixth element of the periodic table with atomic weight 12. The element is a non-metal and has an isotope of 14 C. The structure of the carbon atom underlies all organic chemistry, since all organic substances include carbon molecules.

carbon atom

The position of carbon in the periodic table of Mendeleev:

• sixth serial number;
• fourth group;
• second period.

Rice. 1. Position of carbon in the periodic table.

Based on the data from the table, we can conclude that the structure of the atom of the element carbon includes two shells on which six electrons are located. The valency of carbon included in organic substances is constant and equal to IV. This means that the outer electronic level has four electrons, and the inner level has two.

Of the four electrons, two occupy a spherical 2s orbital, and the remaining two occupy a 2p dumbbell orbital. In an excited state, one electron from the 2s orbital goes to one of the 2p orbitals. When an electron moves from one orbital to another, energy is expended.

Thus, an excited carbon atom has four unpaired electrons. Its configuration can be expressed by the formula 2s 1 2p 3. This makes it possible to form four covalent bonds with other elements. For example, in a methane molecule (CH4), carbon forms bonds with four hydrogen atoms - one bond between the s orbitals of hydrogen and carbon and three bonds between the p orbitals of carbon and the s orbitals of hydrogen.

The structure of the carbon atom can be represented as +6C) 2) 4 or 1s 2 2s 2 2p 2.

Rice. 2. Structure of the carbon atom.

Physical properties

Carbon occurs naturally in the form of rocks. Several allotropic modifications of carbon are known:

• graphite;
• diamond;
• carbine;
• coal;
• soot.

All these substances differ in the structure of their crystal lattice. The hardest substance, diamond, has the cubic form of carbon. At high temperatures, diamond turns into graphite with a hexagonal structure.

Rice. 3. Crystal lattices of graphite and diamond.

Chemical properties

The atomic structure of carbon and its ability to attach four atoms of another substance determine the chemical properties of the element. Carbon reacts with metals to form carbides:

• Ca + 2C → CaC 2;
• Cr + C → CrC;
• 3Fe + C → Fe 3 C.

Also reacts with metal oxides:

• 2ZnO + C → 2Zn + CO 2 ;
• PbO + C → Pb + CO;
• SnO 2 + 2C → Sn + 2CO.

At high temperatures, carbon reacts with non-metals, in particular hydrogen, forming hydrocarbons:

C + 2H 2 → CH 4.

With oxygen, carbon forms carbon dioxide and carbon monoxide:

• C + O 2 → CO 2;
• 2C + O 2 → 2СО.

Carbon monoxide is also formed when it interacts with water.