Where carbon is contained. Carbon is the characteristic of the element and chemical properties. Examples of solving problems

Diamond structure (but) and graphite (b)

Carbon (Latin Carboneum.) - C, chemical element IV group of periodic Mendeleev system, atomic number 6, atomic weight 12,011. It is found in nature in the form of diamond crystals, graphite or fullerene and other forms and is part of organic (coal, oil, organisms of animals and plants, etc.) and inorganic substances (limestone, food soda, etc.). Carbon is widespread, but its content in the earth's crust is only 0.19%.

Carbon is widely used in the form of simple substances. In addition to precious diamonds that are the subject of jewelry, industrial diamonds are of great importance - for the manufacture of grinding and cutting tools. Charcoal and other amorphous carbon forms are used for discoloration, cleaning, gases adsorption, in the fields of technology where adsorbents with a developed surface are required. Carbides, carbon compounds with metals, as well as boron and silicon (for example, Al 4 C 3, SiC, B 4 C) are characterized by high hardness and are used for the manufacture of an abrasive and cutting tool. Carbon is part of steels and alloys in elemental state and in the form of carbides. The saturation of the surface of steel castings by carbon at high temperature (cementation) significantly increases surface hardness and wear resistance.

Historical reference

Graphite, diamond and amorphous carbon are known from antiquity. It is known that graphite can be labeled another material, and the name "graphite" originating from the Greek word meaning "writing", proposed by A.Verner in 1789. However, the history of graphite is infant, often received substances with similar external physical properties for it. , for example, molybdenite (molybdenum sulfide), one time considered graphite. Among other graphite names are famous "black lead", "carbide iron", "silver lead".

In 1779, K. Level found that graphite can be oxidized with air to form carbon dioxide. For the first time, diamonds found an application in India, and in Brazil, precious stones acquired a commercial significance in 1725; The deposit in South Africa was open in 1867.

In the 20th century The main manufacturers of diamond are South Africa, Zaire, Botswana, Namibia, Angola, Sierra Leone, Tanzania and Russia. Artificial diamonds whose technology was created in 1970 are manufactured for industrial purposes.

Properties

Four crystal carbon modifications are known:

• graphite,
• diamond,
• carbin,
• lonsdaleit.

Graphite - gray-black, opaque, fat to the touch, scaly, very soft mass with a metal glitter. At room temperature and normal pressure (0.1 MN / m 2, or 1 kgf / cm 2) graphite is thermodynamically stable.

Diamond - Very hard, crystalline substance. Crystals have a cubic grazenarized grid. At room temperature and normal pressure, diamond metastable. 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 carbon can be obtained at pressures above 10.5 MN / m 2 (105 kgf / cm 2) and temperatures above 3700 ° C. For solid carbon (coke, soot, charcoal) is also characterized by a state with an unordered structure - the so-called "amorphous" carbon, which does not constitute an independent modification; The basis of its structure is the structure of small-crystalline graphite. Heating some varieties of "amorphous" carbon above 1500-1600 ° C without air access causes them to transform into graphite.

The physical properties of the "amorphous" carbon are very dependent on the dispersion of particles and the presence of impurities. Density, heat capacity, thermal conductivity and electrical conductivity of "amorphous" carbon is always higher than graphite.

Karbin Received artificially. It is a small crystalline black powder (density of 1.9-2 g / cm 3). Built from long chains of atoms FROMlaid parallel to each other.

Lonsdaleit found in meteorites and obtained artificially; Its structure and properties are finally installed.

Carbon properties
Atomic number		6
Atomic mass		12,011
Isotopes:	stable	12, 13
	unstable	8, 9, 10, 11, 14, 15, 16, 17, 18, 19, 20, 21, 22
Melting temperature		3550 ° C.
Boiling temperature		4200 ° C.
Density		1.9-2.3 g / cm 3 (graphite) 3.5-3.53 g / cm 3 (diamond)
Hardness (MOO)		1-2
Contents in the earth's crust (mass.)		0,19%
Oxidation degree		-4; +2; +4

Alloys

Steel

Coke is used in metallurgy as a reducing agent. Charcoal - in blacksmith mines, for obtaining powder (75% KNO 3 + 13% C + 12% S), for gases (adsorption), as well as in everyday life. South is used as a filling of rubber, for the manufacture of black paints - typographic paint and mascara, as well as in dry galvanic elements. The glass carbon is used for the manufacture of instruments for highly aggressive media, as well as in aviation and astronautics.

Activated coal absorbs harmful substances from gases and liquids: they are filled with gas masks, cleaning systems, it is used in medicine during poisoning.

Carbon is the basis of all organic substances. Any living organism is largely made of carbon. Carbon is the basis of life. The source of carbon for living organisms is usually CO 2 of the atmosphere or water. As a result of photosynthesis, it enters biological food chains in which living beings eat each other or the remains of each other and thereby mining carbon for the construction of their own body. The biological carbon cycle ends either by oxidation and return to the atmosphere, or the burial in the form of coal or oil.

The use of radioactive isotope 14 C contributed to the successes of molecular biology in the study of the mechanisms of protein biosynthesis 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.

Sources

Chemical elements and materials
Chemical elements	Nitrogen. Argon. Hydrogen. Helium. Iron Calcium. Oxygen. Silicon. Magnesium. Manganese.

Definition

Carbon - Sixth element of the periodic table. Designation - with from Latin "Carboneum". Located in the second period, IVA group. Refers to nonmetallam. The kernel charge is 6.

Carbon is in nature both in free state and in the form of numerous connections. Free carbon is found in the form of diamond and graphite. In addition to fossil coal, large accumulations of oil are in the depths of the Earth. In the earth's crust there are in huge amounts of carbonic acid salts, especially calcium carbonate. There are 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 common on Earth, although its overall content in the earth's crust is only about 0.1% (mass.).

Atomic and molecular weight of carbon

The relative molecular weight of the substance (M R) is a number indicating how many times the mass of this molecule is greater than 1/12 mass of the carbon atom, and the relative atomic mass of the element (A R) is how many times the average weight of the chemical element atoms is greater than 1/12 Masses of carbon atom.

Since in the free state of carbon exists in the form of single-nation molecules C, the values \u200b\u200bof its atomic and molecular masses coincide. They are equal to 12.0064.

Allotropy and allotropic carbon modifications

In the free state of carbon exists in the form of a diamond crystallizing in cubic and hexagonal (LonsDelit) system, and graphite belonging to the hexagonal system (Fig. 1). Such carbon forms like charcoal, coke or soot have an unordered structure. Also, there are also allotropic modifications obtained by synthetic means - it is carbon and polycumilen - types of carbon, constructed from linear chain polymers like -c \u003d c- or \u003d c \u003d c \u003d.

Fig. 1. Allotropic carbon modifications.

Allotropic carbon modifications are also known, having the following names: graphene, fullerene, nanotubes, nanofibre, astlanela, glass border, colossal nanotubes; Amorphous carbon, carbon nanople and carbon nano.

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 kernel of the carbon isotope atom 12 C contains six protons and six neutrons, and the 13 C isotope is the same number of protons and five neutrons.

There is one artificial (radioactive) carbon isotope 14 SS half-life for 5730 years.

Carbon ions

At the external energy level of the carbon atom there are four electrons that are valence:

1s 2 2S 2 2P 2.

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

C 0 -2E → C 2+;

C 0 -4E → C 4+;

With 0 + 4e → with 4-.

Molecule and carbon atom

In the free state of carbon exists in the form of single-name molecules C. We present some properties characterizing the atom and carbon molecule:

Carbon alloys

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

Examples of solving problems

Example 1.

The task	What volume of carbon oxide (IV) is highlighted (N.U.) during the firing of 500 g of limestone containing 0.1 mass fraction of impurities.
Decision	We write limestone roasting reaction equation: Caco 3 \u003d Cao + CO 2 -. We find a lot of pure limestone. To do this, first we will define its mass fraction without impurities: w Clear (CaCo 3) \u003d 1 - W impairity \u003d 1 - 0.1 \u003d 0.9. m Clear (Caco 3) \u003d M (Caco 3) × W Clear (Caco 3); m Clear (Caco 3) \u003d 500 × 0.9 \u003d 450 Calculate the amount of limestone substance: n (Caco 3) \u003d M Clear (Caco 3) / M (Caco 3); n (Caco 3) \u003d 450/100 \u003d 4.5 mol. According to the reaction equation N (Caco 3): N (CO 2) \u003d 1: 1, it means n (Caco 3) \u003d n (CO 2) \u003d 4.5 mol. Then, the volume of highlighted carbon oxide (IV) will be equal to: V (CO 2) \u003d n (CO 2) × V m; V (CO 2) \u003d 4.5 × 22.4 \u003d 100.8 l.
Answer	100.8 L.

Example 2.

The task	How much is a solution that contains 0.05 mass fractions, or 5% of chloroodor, for neutralization of 11.2 g calcium carbonate?
Decision	We write the equation of the calcium carbonate neutralization reaction with chloride: Caco 3 + 2HCl \u003d CaCl 2 + H 2 O + CO 2 -. Find the amount of calcium carbonate substance: M (Caco 3) \u003d a R (Ca) + a R (c) + 3 × a R (o); M (Caco 3) \u003d 40 + 12 + 3 × 16 \u003d 52 + 48 \u003d 100 g / mol. n (Caco 3) \u003d M (CaCO 3) / M (Caco 3); n (Caco 3) \u003d 11.2 / 100 \u003d 0,112 mol. According to the reaction equation N (Caco 3): N (HCl) \u003d 1: 2, it means n (HCl) \u003d 2 × n (Caco 3) \u003d 2 × 0,224 mol. We define the mass of the substance of the chlorine-produce contained in the solution: M (HCl) \u003d a r (h) + a R (Cl) \u003d 1 + 35.5 \u003d 36.5 g / mol. m (HCl) \u003d n (HCl) × M (HCl) \u003d 0.224 × 36,5 \u003d 8,176 Calculate the mass of the solution of chloroodorodor: m Solution (HCl) \u003d M (HCl) × 100 / W (HCl); m Solution (HCl) \u003d 8.176 × 100/5 \u003d 163.52
Answer	163.52

Carbon (from Latin: Carbo "Coal") is a chemical element with a symbol with and atomic number 6. To form covalent chemical bonds, four electrons are available. The substance is non-metallic and twisted. Three carbon isotop are naturally found, 12C and 13C are stable, and 14C is a radioactive isotope, fading with a half-life of about 5730 years. Carbon is one of the few elements known from antiquity. Carbon is the 15th most common element in the earth's crust, and the fourth most common element in the universe by weight after hydrogen, helium and oxygen. The abundance of carbon, the unique variety of its organic compounds and its unusual ability to form polymers at temperatures commonly found on Earth allow this element to serve as a common element for all known life forms. This is the second most common element in the human body by mass (about 18.5%) after oxygen. Carbon atoms can be associated differently, called carbon altypes. The most famous allotruops are graphite, diamond and amorphous carbon. The physical properties of carbon are widely vary depending on the allotropic form. For example, graphite is opaque and black, and the diamond is very transparent. Graphite is soft enough to form a strip on paper (hence the name and its name, from the Greek verb "Γράφειν", which means "writing"), while the diamond is the most firm-known material in nature. Graphite is a good electric conductor, and the diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes and graphene have the highest thermal conductivity among all known materials. All carbon allotropics are solid substances in normal conditions, and graphite is the most thermodynamically stable form. They are chemically stable and require high temperatures to react even with oxygen. The most common state of carbon oxidation in inorganic compounds is +4, and +2 - in carboxyl complexes of carbon monoxide and transition metal. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant amounts occur from organic sediments of coal, peat, oil and methanate clathrates. Carbon forms a huge number of compounds, more than any other element, with almost a ten millionth amount of compounds described to the present, and, nevertheless, this number is only part of the number of theoretically possible compounds under standard conditions. For this reason, carbon is often referred to as "king of elements".

Characteristics

Carbon allotropics include graphite, one of the milders of known substances, and diamond, the hardest natural substance. Carbon is easily associated with other small atoms, including other carbon atoms, and is capable of forming numerous sustainable covalent bonds with suitable multifaceted atoms. It is known that carbon forms almost ten million different compounds, the overwhelming majority of all chemical compounds. Carbon also has the highest sublimation point among all elements. At atmospheric pressure, it does not have a melting point, since its triple point is 10.8 ± 0.2 MPa and 4600 ± 300 K (~ 4330 ° C or 7,820 ° F), so it is subfeated at a temperature of about 3900 K. Graphite is much more reactive than a diamond, under standard conditions, despite the fact that it is more thermodynamically stable, since its delocalled PI system is much more vulnerable to the attack. For example, graphite can be oxidized by hot concentrated nitric acid under standard conditions to melithic acid C6 (CO2H) 6, which retains hexagonal units of graphite when the larger structure is destroyed. Carbon is removed in a carbon arc, the temperature of which is about 5800 K (5,530 ° C, 9 980 ° F). Thus, regardless of its allotropic form, carbon remains solid at higher temperatures than the highest melting temperatures, such as tungsten or rhenium. Although thermodynamically carbon is inclined to oxidation, it is more resistant to oxidation than elements such as iron and copper, which are more weak reducing agents at room temperature. Carbon - sixth element with electronic configuration of the main state of 1S22S22P2, of which four external electrons are valence electrons. Its first four ionization energies 1086.5, 2352.6, 4620.5 and 6222,7 kJ / mol, much higher than in more severe elements of group 14. Carbon electrothitality is 2.5, which is significantly higher than that of heavier elements 14 of the group (1.8-1.9), but close to most neighboring non-metals, as well as to some transition metals of the second and third row. Covalent carbon radii are usually taken as 77.2 PM (CC), 66.7 PM (C \u003d C) and 60.3 PM (C≡C), although they may vary depending on the coordination number and on what is connected with carbon. In general, a covalent radius decreases with a decrease in the coordination number and increasing the order of relations. Carbon compounds make up the basis of all known forms of life on Earth, and the carbon-nitric cycle provides some energy separated by the Sun and other stars. Although carbon forms an extraordinary variety of compounds, most of the forms of carbon are not relatively reacting in normal conditions. With standard temperatures and pressure, carbon can withstand everything except the strongest oxidizing agents. It does not react with sulfuric acid, hydrochloric acid, chlorine or alkalis. At elevated temperatures, carbon reacts with oxygen to form carbon oxides and removes oxygen from metal oxides, leaving element metal. This exothermic reaction is used in ferrous metallurgy for smelting iron and carbon monitoring in steel:

Fe3O4 + 4 C (S) → 3 Fe (S) + 4 CO (G)

with gray with the formation of carbon disulfide and with ferry in the reaction of coal gas:

C (S) + H2O (G) → CO (G) + H2 (G)

Carbon is combined with some metals at high temperatures with the formation of metal carbides, such as cemented iron carbide in steel and tungsten carbide, widely used as an abrasive and for the manufacture of hard tips for cutting tools. The carbon allotropic system covers a number of extremes:

Some types of graphite are used for thermal insulation (for example, fireproof obstacles and heat shields), but some other forms are good thermal conductors. Diamond is the most famous natural thermal conductory. Graphite is opaque. Diamond is very transparent. Graphite crystallizes in a hexagonal system. Diamond crystallizes in the cubic system. Amorphous carbon is completely isotropic. Carbon nanotubes are one of the most famous anisotropic materials.

Allhotropics of carbon

Atomic carbon is a very short-lived type, and therefore carbon stabilizes in various polytomic structures with various molecular configurations called altypes. Three relative to the well-known carbon altyreop are amorphous carbon, graphite and diamond. Previously considered exotic, fullerenes are currently typically synthesized and used in studies; They include baccologists, carbon nanotubes, carbon nano-nanofolk. Several other exotic allotropov, such as lanslytite, glass carbon, carbon nanofuum and linear acetylene carbon (carbon), were also discovered. As of 2009, graphene is considered the strongest material among all ever tested. The process of separating it from graphite will require some further technological development before it becomes economical for industrial processes. In case of success, graphene can be used in the construction of space elevators. It can also be used to safely storing hydrogen for use in hydrogen-based engines in vehicles. The amorphous form is a set of carbon atoms in non-crystalline, irregular, vitreous state, and not contained in the crystal macrostructure. It is present in the form of a powder and is the main component of substances such as charcoal, a lamp smoke (soot) and activated carbon. During normal pressures, carbon has a graphite form in which each atom is trigonally connected by three other atoms in a plane consisting of fused hexagonal rings, as in aromatic hydrocarbons. The obtained network is two-dimensional, and the obtained flat sheets are folded and freely binds through the weak forces of Van der Waals. This gives graphite its softness and splitting properties (sheets easily slipped over each other). Due to the delocalization of one of the external electrons of each atom with the formation of the π-cloud, graphite carries out electricity, but only in the plane of each covalently associated sheet. This leads to lower carbon electrical conductivity than for most metals. Delocalization also explains the energy stability of graphite on the diamond at room temperature. At very high pressures, carbon forms a more compact allotrop, a diamond having almost twice as high density than graphite. Here, each atom is tetrahedrically connected to four others, forming a three-dimensional network of wrinkled six-membered rings of atoms. Diamond has the same cubic structure that silicon and germanium, and due to the strength of carbon-carbon ties, it is the most solid natural substance, which is measured by resistance to scratches. Contrary to the common belief that "diamonds are eternal", they are thermodynamically unstable under normal conditions and turn into graphite. Due to the high energy barrier of activation, the transition into the form of graphite is so slow at normal temperature that it is immeasured. Under some conditions, carbon is crystallized as a locality, a hexagonal crystal lattice with all covalently connected atoms and properties similar to the properties of diamond. Fullerenes are a synthetic crystalline formation with a graphite-like structure, but instead of the hexagons of fullerenes consist of pentagons (or even seven-angry) carbon atoms. Missing (or additional) atoms deform sheets in spheres, ellipses or cylinders. The properties of fullerenes (divided into bascols, baktyubs and nanobada) are not yet fully analyzed and represent an intensive area of \u200b\u200bresearch of nanomaterials. The names "Fullerene" and "Bakol" are associated with the name of Richard of Buckminster Fuller, a popularizer of geodesic domes that resemble the structure of fullerenes. Bakabols are rather large molecules formed entirely from carbon ties trigonally, forming spheroids (the most famous and simplest is a buxinisterfellerine C60 with a form of a soccer ball). Carbon nanotubes are structurally similar to Bakibol, except that each atom is associated with a trigonally in a curved sheet that forms a hollow cylinder. Nanobada was first presented in 2007 and are hybrid materials (baccabols are covalently linked to the outer wall of the nanotubes), which combine the properties of both in the same structure. From other allotropov detected, carbon nano beam is a ferromagnetic allotropist discovered in 1997. It consists of a cluster assembly of low-density carbon atoms stretched together in a loose three-dimensional network, in which the atoms are trigomally connected in six-seed rings. It refers to the number of lighter solids with a density of about 2 kg / m3. Similarly, glass-like carbon contains a high proportion of closed porosity, but, unlike ordinary graphite, graphite layers are not complicated as pages in the book, but have a more random location. Linear acetylene carbon has a chemical structure - (C ::: C) N-. Carbon in this modification is linear with orbital hybridization SP and is a polymer with alternating single and triple bonds. This carbine is considerable interest for nanotechnology, since its Jung module is forty times more than that of the solid material - diamond. In 2015, the team from the University of North Carolina announced the development of another alhotreop, which they called q-carbon, created by a highly energy laser pulse of low durability on amorphous carbon dust. It is reported that the Q-carbon exhibits ferromagnetism, fluorescence and has a hardness superior to diamonds.

Prevalence

Carbon is the fourth in the prevalence of the chemical element in the universe by weight after hydrogen, helium and oxygen. Carbon replete in the sun, stars, comets and atmospheres of most planets. Some meteorites contain microscopic diamonds that were formed when the solar system was still a protoplanetic disk. Microscopic diamonds can also be formed at intensive pressure and high temperature in places of exposure to meteorite. In 2014, NASA announced an updated database for tracking polycyclic aromatic hydrocarbons (PAU) in the Universe. More than 20% of carbon in the universe can be associated with PAH, complex compounds of carbon and hydrogen without oxygen. These compounds appear in the global hypothesis of PAU, where they presumably play a role in the abiogenesis and the formation of life. It seems that PAU was formed "after a couple of billion years" after a large explosion, widespread in the universe and are associated with new stars and exoplanets. It is estimated that the firm shell of the Earth, in general, contains 730 CNM carbon, while 2000 ppm is contained in the core and 120 pm in the combined mantle and the crust. Since the mass of the Earth is 5.9 72 × 1024 kg, it will mean 4360 million carbon gigaton. It is much larger than the amount of carbon in the oceans or the atmosphere (below). In combination with oxygen in carbon dioxide, carbon is in the Earth's atmosphere (approximately 810 carbon gigaton) and dissolves in all water bodies (approximately 36,000 carbon gigaton). In the biosphere there are about 1900 carbon gigaton. Hydrocarbons (such as coal, oil and natural gas) also contain carbon. Coal "reserves" (and not "resources") account for about 900 gigaton C, perhaps 18,000 HT resources. Oil reserves make up about 150 gigaton. Proved natural gas sources are about 175,1012 cubic meters (containing about 105 carbon gigatons), but 900 1012 cubic meters of "non-traditional" deposits, such as shale gas, are estimated in studies, which is about 540 carbon gigaton. Carbon was also discovered in methane hydrates in polar regions and under the seas. According to different estimates, the amount of this carbon is 500, 2500 gt, or 3000 gt. In the past, the amount of hydrocarbons was more. According to one source, in the period from 1751 to 2008, about 347 carbon gigatons were thrown into the atmosphere in the form of carbon dioxide into the atmosphere from burning fossil fuels. Another source adds the amount added to the atmosphere from 1750 to 879 GT, and the total amount in the atmosphere, the sea and earth (for example, peat swamps) is almost 2000 GT. Carbon is an integral part (12% by weight) of very large masses of carbonate rocks (limestone, dolomite, marble, etc.). Coal contains a very large amount of carbon (anthracite contains 92-98% carbon) and is the largest commercial source of mineral carbon, which accounts for 4,000 gigaton or 80% of fossil fuels. As for individual altostrops of carbon, graphite is contained in large quantities in the United States (mainly in New York and Texas), in Russia, Mexico, Greenland and India. Natural diamonds are found in the mountain kimberlite contained in ancient volcanic "necks" or "pipes". Most diamond fields are in Africa, especially in South Africa, Namibia, Botswana, the Republic of Congo and Sierra Leone. Diamond fields were also found in Arkansas, Canada, Russian Arctic, Brazil, as well as in North and Western Australia. Now diamonds are also removed from the bottom of the ocean at the Cape of Good Hope. Diamonds are found naturally, but now about 30% of all industrial diamonds used in the United States are produced. Carbon-14 is formed in the upper layers of the troposphere and the stratosphere at altitudes of 9-15 km in the reaction, which is deposited by the cosmic rays. Thermal neutrons are manufactured, which face nitrogen-14 nuclei, forming carbon-14 and proton. Thus, 1.2 × 1010% of atmospheric carbon dioxide contains carbon-14. Asteroids rich in carbon are relatively dominated in the outer parts of the belt of asteroids in our solar system. These asteroids have not been directly investigated by scientists. Asteroids can be used in a hypothetical coal based on outer space, which may be possible in the future, but is currently technologically impossible.

Carbon isotopes

Carbon isotopes are atomic kernels that contain six protons plus a number of neutrons (from 2 to 16). Carbon has two stable found in nature, isotope. Carbon-12 isotope (12c) forms 98.93% of carbon on Earth, and carbon-13 (13c) forms the remaining 1.07%. The concentration of 12C is further increased in biological materials, because the biochemical reactions discriminate 13c. In 1961, the International Union of Clean and Applied Chemistry (Jupak) adopted isotopic carbon-12 as the basis for atomic scales. Carbon identification in experiments with nuclear magnetic resonance (NMR) is carried out with an isotope 13c. Carbon-14 (14C) is a natural radioisotope created in the upper atmosphere (lower stratosphere and upper troposphere) by interacting with nitrogen with cosmic rays. It is in trace quantities on Earth in an amount of up to 1 part per trillion (0.0000000001%), mainly in the atmosphere and surface sediments, in particular, peat and other organic materials. This isotope disintegrates in the course of β-emission 0.158 MeV. Due to a relatively short period of half-life, 5730 years old, 14C is practically absent in the ancient rocks. In the atmosphere and in living organisms, the amount of 14C is almost constant, but decreases in organisms after death. This principle is used in radiocarbon dating, invented in 1949, which was widely used to determine the age of carbon materials with age up to 40,000 years. There are 15 known carbon isotopes and the smallest life of them from them has 8C, which disintegrates due to the emission of protons and alpha decay and has a half-life of 1,98739 × 10-21 s. Exotic 19C demonstrates nuclear halo, which means that its radius is much greater than it could be expected if the core was a sphere of constant density.

Education in the stars

The formation of a carbon nucleus requires an almost simultaneous triple collision of alpha particles (helium nuclei) inside the core of a giant or supergigant star, which is known as the triple alpha process, since the products of further reactions of the helium nuclear synthesis with hydrogen or other helium core are produced by lithium-5 and beryllium. -8, respectively, both of which are very unstable and almost instantly fade back into smaller kernels. This occurs in temperatures of more than 100 megakalvin and the concentration of helium, which is unacceptable in conditions of rapid expansion and cooling of the early universe, and therefore there were no significant amounts of carbon during a large explosion. According to the modern theory of physical cosmology, carbon is formed inside the stars in the horizontal branch by collision and the transformation of the three helium nuclei. When these stars die as a supernova, carbon is dissipated into space in the form of dust. This dust becomes a composite material for the formation of stellar systems of the second or third generation with accreated planets. The solar system is one of these stellar systems with an abundance of carbon, allowing the existence of life as we know it. CNO cycle is an additional merger mechanism that controls the stars where carbon works as a catalyst. Rotary transitions of various isotopic forms of carbon monoxide (for example, 12CO, 13CO and 18CO) are detected in the submillimeter wavelength range and are used in the study of new-generated stars in molecular clouds.

Carbon cycle

On earthly conditions, the conversion of one element to another - the phenomenon is very rare. Therefore, the amount of carbon on Earth is effectively constant. Thus, in the processes that carbon use, it must be obtained from somewhere and disposed of elsewhere. Carbon paths in the environment form a carbon cycle. For example, photosynthetic installations extract carbon dioxide from the atmosphere (or sea water) and build it in biomass, as in the Calvin cycle, carbon fixation process. Some of this biomass is eaten by animals, while some carbon exhales animals in the form of carbon dioxide. The carbon cycle is much more complicated than this short cycle; For example, a certain amount of carbon dioxide dissolves in the oceans; If bacteria do not absorb it, the dead vegetable or animal substance can become oil or coal, which highlights carbon when burning.

Carbon compounds

Carbon can form very long chains of interrelated carbon-carbon bonds, a property called the formation of chains. Carbon-carbon bonds are stable. Thanks to the catanation (chains formation), carbon forms countless connections. The assessment of unique compounds shows that a larger amount of them contain carbon. A similar statement can be made for hydrogen, because most organic compounds also contain hydrogen. The simplest form of an organic molecule is a hydrocarbon - a large family of organic molecules, which consist of hydrogen atoms associated with a chain of carbon atoms. Chain length, side chains and functional groups affect the properties of organic molecules. Carbon is found in all forms of famous organic life and is the basis of organic chemistry. When combining with hydrogen, carbon forms various hydrocarbons, which are important for industry as refrigerants, lubricants, solvents, as chemical raw materials for the production of plastics and petroleum products, as well as fossil fuels. In combination with oxygen and hydrogen, carbon can form many groups of important biological compounds, including sugars, lignas, chitins, alcohols, fats and aromatic esters, carotenoids and terpenes. With nitrogen, carbon forms alkaloids, and with the addition of sulfur also forms antibiotics, amino acids and rubber products. With the addition of phosphorus to these other elements, it forms DNA and RNA, the carriers of the chemical code of life and adenosinerphosphate (ATP), the most important molecule of energy transfer in all living cells.

Inorganic compounds

Usually carbon-containing compounds that are associated with minerals or which do not contain hydrogen or fluorine, processed separately from classical organic compounds; This definition is not strict. Among them are simple carbon oxides. The most famous oxide is carbon dioxide (CO2). Once this substance was the main component of the Paleoatmosphere, but today is the secondary component of the atmosphere of the Earth. When dissolved in water, this substance forms carbon dioxide (H2CO3), but, like most compounds with several single-connected oxygen on one carbon, it is unstable. However, resonant stabilized carbonate ions are formed through this intermediate. Some important minerals are carbonates, especially calcite. Carbon disulfide (CS2) is similar. Another common oxide is carbon monoxide (CO). It is formed with incomplete combustion and is a colorless gas without smell. Each molecule contains a triple bond and is rather polar, which leads to the fact that it is constantly associated with hemoglobin molecules, displacing oxygen, which has a lower affinity of binding. Cyanide (CN-) has a similar structure, but he behaves like halide ions (pseudogalogen). For example, it can form cyanogen nitride molecule (CN) 2), similar to diatomal halides. Other unusual oxides are carbon suboxide (C3O2), unstable carbon monoxide (C2O), carbon trioxide (CO3), cyclopentanepepton (C5O5), cyclohexanegexon (C6O6) and mellite anhydride (C12O9). With reactive metals, such as tungsten, carbon forms either carbides (C4-), or acetylides (C2-2) with the formation of alloys with high melting temperatures. These anions are also associated with methane and acetylene, both of which are very weak acids. During electrothy 2.5, carbon prefers to form covalent bonds. Several carbides are covalent lattices, such as carborund (SiC), which resembles a diamond. However, even the most polar and saline carbides are not completely ionic connections.

Metallometallic connections

Organometallic compounds, by definition, contain at least one carbon-metal connection. There is a wide range of such compounds; The main classes include alkyl-metal alkyl compounds (for example, tetraethyl eleyl), η2-alkene compounds (for example, Zeise salt) and η3-allyl compounds (for example, allylpalladium chloride dimer); Metallocenes containing cyclopentadienyl ligands (for example, ferrocene); and carbenic metals complexes. There are many carbonyls of metals (for example, tetracarboonylnicel); Some workers believe that carbon monoxide ligand is purely inorganic, not metallo-organic, compound. While it is believed that carbon solely forms four bonds, it is reported on an interesting compound containing an octahedral hexacoordinated carbon atom. The cation of this compound is 2+. This phenomenon is explained by the Aurophilicity of the Golden Ligands. In 2016, it was confirmed that hexamethylbenzene contains a six-tone carbon atom, and with not ordinary four.

History and etymology

The English carbon name (Carbon) comes from Latin Carbo, denoting "coal" and "charcoal", from here the French word Charbon, which means "charcoal". In German, Dutch and Danish, carbon titles - Kohlenstoff, Koolstof and Kulstof, respectively, everyone literally means a coal substance. Carbon was discovered in prehistoric times and was known in soot and charcoal forms in the earliest human civilizations. Diamonds were known, probably already in 2500 BC. In China, and carbon in the form of charcoal was made in Roman times by the same chemistry as today, by heating wood in a pyramid, covered with clay to eliminate air. In 1722, Rene Antooman Ferho Deamamur demonstrated that iron turns into steel through the absorption of any substance that is now known as carbon. In 1772, Antoine Lavauzier showed that diamonds are carbon form; When he burned samples of charcoal and diamond and found that none of them produced no water, and that both substances produced an equal amount of carbon dioxide per gram. In 1779, Karl Wilhelm Shelele showed that graphite, which was considered a lead shape, instead was identical to charcoal, but with a small impurity of iron and that he gave "aircroic acid" (which is carbon dioxide) during oxidation of nitric acid. In 1786, French scientists Claude Louis Bertoll, Gaspard Montj and K. A. Vandermond confirmed that graphite was mainly carbon, when it was oxidized in oxygen, almost the same as Lavoisie did with a diamond. A certain amount of iron remained again, which, according to French scientists, was necessary for the structure of graphite. In his publication, they offered the name Carbone (Carbonum Latin word) for an element in graphite, which was released as gas when burning graphite. Then Antoine Lavoisier listed carbon as an element in its 789 textbook. The new carbon alllestop, fullerene, which was discovered in 1985, includes nanostructured forms, such as baccakes and nanotubes. Their discovers - Robert Kerl, Harold Malo and Richard Smallley - received the Nobel Prize in Chemistry in 1996. The resulting renewed interest in new forms leads to the opening of additional exotic allotrops, including glass-like carbon, and the realization that "amorphous carbon" is not strictly amorphous.

Production

Graphite

Commercially viable natural deposits of graphite are found in many parts of the world, but the most economically important sources are located in China, India, Brazil and North Korea. Graphite deposits have a metamorphic origin, detected in combination with quartz, mica and field swaps in slates, gneis and metamorphic sandstones and limestones in the form of lenses or lived, sometimes thick in a few meters or more. Graphite stocks in Borroudle, Cumberland, England, were at the beginning of a sufficient size and purity, so until the 19th century, the pencils were made simply by sawing blocks from natural graphite on the strips before sticking the strips in the wood. Today, smaller grate deposits are obtained by grinding parental breed and swimming easier graphite on water. There are three types of natural graphite - amorphous, scaly or crystalline. Amorphous graphite has the lowest quality and is the most common. Unlike science, in the amorphous industry refers to a very small size of the crystal, and not to the complete absence of a crystal structure. The word "amorphous" is used to designate products with a low amount of graphite and is the cheapest graphite. Large deposits of amorphous graphite are located in China, Europe, Mexico and the United States. Flat graphite is less common and has a higher quality than amorphous; It looks like separate plates that crystallized in metamorphic rocks. The price of granular graphite can four times exceed the price of amorphous. Cachet graphite of good quality can be recycled in expandable graphite for many applications, such as anti-epires. Primary graphite deposits are located in Austria, Brazil, Canada, China, Germany and Madagascar. Liquid or lump graphite is the most rare, most valuable and high-quality type of natural graphite. It is in the veins along the intrusive contacts in solid scenes, and is commercially mined only in Sri Lanka. According to USGS, world natural graphite production in 2010 amounted to 1.1 million tons, while 800,000 tons were produced in China, 130,000 tons in Brazil - 76,000 tons, in North Korea - 30,000 tons and Canada - 25,000 tons. No natural graphite was mined in the United States, but in 2009 118,000 tons of synthetic graphite were produced with an estimated value of $ 998 million.

Diamond

Diamond supplies are controlled by a limited number of businesses, as well as highly concentrated in a small number of places around the world. Only a very small fraction of diamond ore consists of real diamonds. Ruda is crushed during which it is necessary to take measures to prevent the destruction of large diamonds in this process, and then the particles are sorted by density. Today, diamonds are mined in fractions with rich diamonds using X-ray fluorescence, after which the last steps of sorting are performed manually. Prior to the use of X-ray use, the separation was carried out using lubricants; It is known that diamonds were discovered only in alluvial sediments in southern India. It is known that diamonds are more inclined to stick to mass than other minerals in ore. India was the leader in the production of diamonds from the moment of their opening in about the 9th century BC until the mid-18th century of our era, but the commercial potential of these sources was exhausted by the end of the 18th century, and by that time India was brazilized by Brazil, where the first diamonds were found In 1725. Diamond production of primary deposits (kimberlites and lamproitts) began only in the 1870s, after the discovery of diamond fields in South Africa. Diamond production increased over time, and only 4.5 billion carats were accumulated from this date. About 20% of this quantity was mined only over the past 5 years, and over the past ten years, 9 new deposits began, and 4 more are waiting for a quick discovery. Most of these deposits are located in Canada, Zimbabwe, Angola and one thing in Russia. In the United States, diamonds were discovered in Arkansas, Colorado and Montana. In 2004, the striking discovery of the microscopic diamond in the United States led to the release in January 2008 mass selection of samples of kimberlite pipes in the remote part of Montana. Today, most commercially viable diamond fields are located in Russia, Botswana, Australia and the Democratic Republic of the Congo. In 2005, Russia made almost one fifth of the global phase of diamonds, according to the British geological service. In Australia, the richest diamantic pipe reached peak production levels in 42 metric tons (41 tons, 46 short tons) per year in the 1990s. There are also commercial fields, the active production of which are carried out in the North-Western territories of Canada, Siberia (mainly in the territory of Yakutia, for example, in the Peace tube and in a successful pipe), in Brazil, as well as in North and Western Australia.

Applications

Carbon is necessary for all well-known living systems. Without it, the existence of life is impossible, such as we know her. The main economic use of carbon, except food and wood, refers to hydrocarbons, first of all, to fossil fuel by methane gas and crude oil. Crude oil is processed by refinery for gasoline, kerosene and other products. Cellulose is a natural carbon-containing polymer produced by plants in the form of a tree, cotton, flax and cannabis. Cellulose is used mainly to maintain the structure of plants. Commercially valuable carbon polymers of animal origin include wool, cashmere and silk. Plastics are made of synthetic carbon polymers, often with oxygen and nitrogen atoms included through regular intervals to the main polymer chain. Raw materials for many of these synthetic substances comes from crude oil. The use of carbon and its compounds is extremely diverse. Carbon can form alloys with iron, the most common of which is carbon steel. Graphite is combined with clays, forming "lead" used in pencils used for writing and drawing. It is also used as lubrication and pigment as a molding material in the production of glass, in electrodes for dry batteries and galvanization and galvanoplasty, in brushes for electric motors and as a neutron retarder in nuclear reactors. Coal is used as a material for the manufacture of works of art, as a grill for a barbecue, for smelting iron and has many other applications. Wood, coal and oil are used as fuel for energy production and heating. High quality diamonds are used in the production of jewelry, and industrial diamonds are used for drilling, cutting and polishing tools for processing metals and stone. Plastics are made of fossil hydrocarbons, and carbon fiber made by pyrolysis of synthetic polyester fibers is used to reinforce plastics with the formation of advanced, light composite materials. Carbon fiber is made by pyrolysis of extruded and stretched threads of polyacrylonitrile (PAN) and other organic substances. The crystal structure and mechanical properties of the fiber depend on the type of source material and subsequent processing. Carbon fibers made of Pan have a structure that resembles narrow graphite threads, but heat treatment can reorder the structure into a continuous sheet. As a result, the fibers have a higher specific tensile strength than steel. Carbon soot is used as a black pigment in printed paints, oil paint and watercolors of artists, carbon paper, automotive finish, ink and laser printers. Carbon soot is also used as a filler in rubber products, such as tires and plastic connections. Activated carbon is used as an absorbent and adsorbent in filter materials in such a variety of applications as gas masks, water purification and kitchen hoods, as well as in medicine to absorb toxins, poisons or gases from the digestive system. Carbon is used in chemical reduction at high temperatures. Coke is used to restore iron ore in the gland (melting). Hardening steel is achieved due to the heating of the finished steel components in the carbon powder. Silicon carbides, tungsten, boron and titanium are among the hardest materials and are used as abrasives for cutting and grinding. Carbon compounds make up most of the materials used in clothing, such as natural and synthetic textiles and leather, as well as almost all inner surfaces in a medium other than glass, stone and metal.

Diamonds

The diamond industry is divided into two categories, one of which is high-quality diamonds (precious stones), and the other - industrial class diamonds. Although there is a large trade in both diamond types, both markets act completely differently. Unlike precious metals, such as gold or platinum, diamonds of precious stones are not traded as goods: on sale diamond there is a significant allowance, and the diamond resale market is not very active. Industrial diamonds are valued, mainly for their hardness and thermal conductivity, while the hemological qualities of clarity and colors are mainly irrelevant. About 80% of the mined diamonds (equal to about 100 million carats or 20 tons per year) are not suitable for use, and are used in industry (diamond scrap). Synthetic diamonds, invented in the 1950s, almost immediately found industrial applications; Every year 3 billion carats (600 tons) of synthetic diamonds are produced. Diamond dominant industrial use is cutting, drilling, grinding and polishing. Most of these applications do not require large diamonds; In fact, most of the diamonds of precious quality, with the exception of small diamonds, can be used in industry. Diamonds are inserted into the tips of the drill or saw blades or are ground into powder for use in grinding and polishing. Specialized applications include using in laboratories as a storage for high pressure experiments, high-performance bearings and limited use in specialized windows. Thanks to the achievements in the production of synthetic diamonds, new applications become practically feasible. Much attention is paid to the possible use of diamond as a semiconductor suitable for microchips, and due to its exceptional thermal conductivity as a radiator in electronics.

Carbon in the periodic system of elements is located in the second period in the IVA group. Electronic configuration of carbon atom lS 2 2S 2 2P 2.When it is excited, an electron state is easily achieved, at which four unpaired electrons are located on four external atomic orbitals:

This explains why carbon in the compounds are usually travelers. Equality in the carbon atom of the number of valence electrons by the number of valence orbitals, as well as the unique ratio of the charge of the kernel and the atom radius reported it the ability to equally easily attach and give electrons depending on the properties of the partner (Section 9.3.1). As a result, carbon is characterized by various degrees of oxidation from -4 to +4 and the ease of hybridization of its atomic orbitals by type sP 3, SP 2and sP 1.in the formation of chemical bonds (sect. 2.1.3):

All this gives carbon the opportunity to form ordinary, double and triple bonds not only among themselves, but also with atoms of other elements-organogen. Molecules formed at the same time may have a linear, branched and cyclic structure.

Due to the mobility of common electrons -Mo, formed with the participation of carbon atoms, their shift towards the atom of a more electronegative element (inductive effect) occurs, which leads to polarity not only of this connection, but also the molecules in general. However, carbon, due to the average electronegability value (0E0 \u003d 2.5), forms weaklyolar communication with the atoms of other element-organogen groups (Table 12.1). In the presence of conjugate bonds in molecules (Section 2.1.3), moving electrons and vapor electronic pairs with alignment of electron density and link lengths in these systems occurs in molecules.

From the position of the reactivity of the compounds, the polarizability of links plays a large role (Section 2.1.3). The greater the polarizability of the connection, the higher its reactivity. The dependence of the polarizability of carbon-containing bonds on their nature reflects the following series:

All considered data on the properties of carbon-containing bonds indicate that carbon in compounds forms, on the one hand, quite strong covalent bonds among themselves and with other organogen groups, and on the other hand, the general electronic pairs of these connections are quite labilic. As a result, it may occur both an increase in the reactivity of these bonds and stabilization. It is these features of carbon-containing compounds and make carbon organogen number one.

Acid-basic properties of carbon compounds.Carbon oxide (4) is acidic oxide, and the appropriate hydroxide-coal acid H2CO3 is weak acid. Molecule of carbon oxide (4) is non-polar, and therefore it is poorly dissolved in water (0.03 mol / l at 298 K). At the same time, the CO2 H2O hydrate is formed in the breaker, in which CO2 is in the cavity of the associate of water molecules, and then this hydrate is slowly and reversibly turns into H2CO3. Most of the carbon oxide dissolved in water (4) is in the form of hydrate.

In the body in the erythrocytes of blood under the action of carrboanhydrase enzyme equilibrium between the hydrate CO2 H2O and H2CO3 is set very quickly. This allows you to neglect the presence of CO2 in the form of hydrate in the erythrocyte, but not in the blood plasma, where there is no carbanenshydrase. The resulting H2CO3 dissociates in physiological conditions to the bicarbonate anion, and in a more alkaline medium - to carbonate anion:

Coalic acid exists only in solution. It forms two rows of salts - hydrocarbonates (Nacanosis, CA (NS0 3) 2) and carbonates (Na2SOs, SASOZ). In water, bicarbonates dissolve better than carbonates. In aqueous solutions of carbonic acid salts, especially carbonates, are easily hydrolyzed by anion, creating an alkaline environment:

Substances such as drinking soda NaHC03; Mel Sasoz, White Magnesia 4MGC03 * MG (OH) 2 * H2O, hydrolyzed with an image formation of an alkaline medium, are used as antacid (neutralizing acids) to reduce increased acidity of gastric juice:

The combination of coalic acid and hydrocarbonate ion (H2CO3, NSO3 (-)) forms a hydrocarbonate buffer system (sect. 8.5) -clavny buffer system of blood plasma, which ensures the constancy of blood pH at pH \u003d 7.40 ± 0.05.

The presence of calcium and magnesium hydrocarbonates in the natural waters causes their temporal rigidity. When boiling such water, its rigidity is eliminated. This is due to the hydrolysis of HCO3 anion (-)), the thermal decomposition of coalic acid and the deposition of calcium and magnesium cations in the form of insoluble CAS0 3 and MG (OH) 2 compounds:

The formation of MG (OH) 2 is caused by the total hydrolysis according to the magnesium cation, flowing under these conditions due to the smaller solubility of Mg (0h) 2 compared to MGC0 3.

In medical and biological practice, in addition to coalic acid, it is necessary to deal with other carbon-containing acids. This is primarily a large set of different organic acids, as well as HCN Sinyl Acid. From the position of acidic properties, the power of these acids is different:

These differences are due to the mutual influence of atoms in the molecule, the nature of dissociating communication and the resistance of anion, i.e. its ability to delocalize charge.

Sinyl Acid, or cyanorrode, HCN - colorless, volatile liquid (T kip \u003d26 ° C) With the smell of bitter almond mixed with water in any ratios. In aqueous solutions, it behaves like very weak acid, the salts of which are called cyanides. Cyanides of alkaline and alkaline earth metals are soluble in water, while they are hydrolyzed by anion, due to which their aqueous solutions smell with blue acid (the smell of bitter almond) and have pH\u003e 12:

With long-term effects of CO2 contained in the air, cyanides are decomposed with the release of blue acid:

As a result of this reaction, potassium cyanide (potassium cyanide) and its solutions with long-term storage losing their toxicity. Cyanide Anion is one of the strongest inorganic poisons, since it is an active ligand and easily forms stable complex compounds with enzymes containing FE 3+ and Cu2 (+) as ionicompleks (sec. 10.4).

Redox properties.Since carbon in compounds may exhibit any degrees of oxidation from -4 to +4, then during the reaction, free carbon can give and attach electrons, acting according to a reducing agent or oxidizing agent, depending on the properties of the second reagent:

In the interaction of strong oxidizing agents with organic substances, incomplete or complete oxidation of carbon atoms of these compounds may occur.

Under conditions of anaerobic oxidation with a lack of or in the absence of oxygen, carbon atoms of an organic compound, depending on the content of oxygen atoms in these compounds and external conditions, can turn into C0 2, CO, C and even CH 4, and the remaining organogens are transformed into H2O, NH3 and H2S .

In the body, the complete oxidation of organic compounds with oxygen in the presence of oxidase enzymes (aerobic oxidation) is described by the equation:

Of the above equations of oxidation reactions, it can be seen that in organic compounds, the degree of oxidation changes only carbon atoms, and the atoms of the remaining organogenons retain their degree of oxidation.

With hydrogenation reactions, i.e., the addition of hydrogen (reducing agent) by multiple bonds, which form its carbon atoms reduce their degree of oxidation (oxidizing):

Organic reactions of substitution with the occurrence of a new intermediate bond, for example, in the Nurez reaction, are also oxidative reactions in which carbon atoms act as oxidizing agents, and metal atoms-removers:

This is observed in the formation of the formation of metallorganic compounds:

At the same time, in the reactions of alkylation with the occurrence of a new intermediate bond, the role of the oxidizing agent and the reducing agent play the carbon atoms of the substrate and the reagent, respectively:

As a result of the reactions of the polar reagent, one of the carbon atoms lowers the degree of oxidation, showing the properties of the oxidant, and the other increases the degree of oxidation, speaking with a reducing agent:

In these cases, the reaction of intramolecular oxidation-restoration of the carbon atoms of the substrate, i.e. the process dysmutationunder the action of a reagent that does not show redox properties.

Typical reactions of intramolecular dumping of organic compounds due to their carbon atoms are the reactions of decarboxylation of amino acids or ketok acids, as well as the reaction of the rearrangement and isomerization of organic compounds, which were considered in Section. 9.3. The examples of organic reactions, as well as the reaction from the section. 9.3 convincingly indicate that carbon atoms in organic compounds can be oxidizers, and reducing agents.

Carbon atom in connection- Oxidizer, if, as a result of the reaction, the number of its bonds with atoms of less electronegative elements increases (hydrogen, metals), because, attracting the general electrons of these bonds, the carbon atom under consideration reduces its degree of oxidation.

Carbon atom in connection- reducing agent if the number of connections with atoms of more electronegative elements increases as a result of the reaction(C, O, N, S), because, repulscing the general electrons of these links from itself, the carbon atom in question increases its degree of oxidation.

Thus, many reactions in organic chemistry due to the oxidative and reductive duality of carbon atoms are redox. However, in contrast to such reactions of inorganic chemistry, the redistribution of electrons between the oxidizing agent and the reducing agent in organic compounds may be accompanied by the displacement of the total electronic pair of chemical bond to the atom that performs the role of the oxidizing agent. In this case, this connection can be maintained, but in cases of a strong polarization, it can be broken.

Complete properties of carbon compounds.In the carbon atom in compounds there are no vulnerable electronic pairs, and therefore only carbon compounds containing multiple relationships with its participation can be ligands. Especially active in the processes of complexation -Electrons of the triple polar communication of carbon monoxide (2) and anion of the sytic acid.

In the carbon oxide molecule (2), carbon and oxygen atoms form one and one-cell due to the mutual overlapping of their two 2r-atomic orbitals on the exchange mechanism. Third Communication, i.e., another-competition, formed according to the donor-acceptor mechanism. The acceptor is the free 2r-atomic or-bits of the carbon atom, and the donor is an oxygen atom, which provides a seenable pair of electrons with 2P orbitals:

Increased multiplicity of communication provides this molecule, high stability and inertia under normal conditions from the position of acid-base (CO - the disadvantageous oxide) and redox properties (CO - reducing agent T\u003e1000 K). At the same time, it makes it an active ligand in complexation reactions with atoms and d-metal cations, primarily with iron, with which it forms pentarbonyl iron - waste toxic liquid:

The ability to form complex compounds with d-metals cations is the cause of the poisonousness of carbon oxide (H) for living systems (section. 10.4) due to the flow of reversible reactions with hemoglobin and oxymemoglobin containing FE 2+ cation, with the formation of carboxygemoglobin:

These equilibrium is shifted towards the formation of carboxygemoglobin NNBSO, the stability of which is 210 times greater than the Oxygemoglobin NNBO2. This leads to the accumulation of carboxygemoglobin in the blood and, therefore, to a decrease in its ability to carry oxygen.

In anonyl acid anion, CN are also contained easily polarizable - electrons, which is why it effectively forms complexes with D-metals, including metals of life included in the enzymes. Therefore, cyanides are highly toxic compounds (sec. 10.4).

Carbon cycle in nature.The carbon cycle in nature is based mainly underlie the oxidation and recovery of carbon (Fig. 12.3).

From the atmosphere and hydrosphere of plants assimilate (1) carbon oxide (4). Part of the plant mass is consumed (2) by man and animals. The respiration of animals and rotting their remains (3), as well as the breath of plants, rotting dead plants and burning wood (4) return the atmosphere and hydrosphere CO2. The process of mineralization of plants (5) and animals (6) with the formation of peat, fossil coal, oil, gas leads to carbon transition to natural fossils. In the same direction, acid-main reactions (7) occur between CO2 and various rocks with the formation of carbonates (medium, acidic and basic):

This inorganic part of the cycle leads to the loss of CO2 in the atmosphere and the hydrosphere. Human activity on the combustion and processing of coal, oil, gas (8), firewood (4), on the contrary, with an excess enriches the environment of carbon oxide (4). For a long time, there was confidence that, thanks to the photosynthesis, CO2 concentration in the atmosphere remains constant. However, at present, an increase in CO2 content in the atmosphere due to human activity is not compensated by its natural loss. The total admission of CO2 into the atmosphere is growing in geometric progression by 4-5% per year. According to calculations in 2000, CO2 content in the atmosphere will reach approximately 0.04% instead of 0.03% (1990).

After considering the properties and features of carbon-containing compounds, it should once again emphasize the leading role of carbon

Fig. 12.3.Carbon Court B. nature

organogen No. 1: First, carbon atoms form the skeleton of organic compound molecules; Secondly, carbon atoms play a key role in oxidative and reduction processes, since the atoms of all organogennes are the most characteristic of the carbon in the carbon. Learn more about the properties of organic compounds - see the IV Module "Basics of Bioorganic Chemistry".

General characteristics and biological role of the R-elements of the IVA group.Electronic carbon counterparts are the elements of the IVA group: silicon Si, germanium GE, Tin SN and lead PB (see Table 1.2). The radii of atoms of these elements is naturally increasing with an increase in the sequence number, and their ionization energy and electronegability are naturally decreasing (sect. 1.3). Therefore, the first two elements of the group: carbon and silicon - typical non-metals, and Germany, tin, lead -metals, as they are most characteristic of the return of electrons. In the GE - SN - PB, metal properties are enhanced.

From the position of the redox properties, the elements C, Si, Ge, Sn and Pb under normal conditions are sufficiently resistant with respect to air and water (SN and PB metals - due to the formation of an oxide film on the surface). At the same time, lead compounds (4) - strong oxidizers:

Comprehensive properties are most characteristic of lead, since its PB 2+ cations are strong complexes in comparison with the cations of the remaining P-elements of the IVA group. Lead cations form strong complexes with bioligands.

The elements of the IVA group differ sharply both by the content in the body and in the biological role. Carbon plays a fundamental role in the vital activity of the body, where its content is about 20%. The content in the body of the remaining elements IVA group is within 10 -6 -10 -3%. At the same time, if silicon and germanium are undoubtedly playing an important role in the life of the body, the tin and especially lead is toxic. Thus, with the growth of the atomic mass of the IVA elements, the toxicity of their compounds increases.

Dust consisting of SiO2 coal coal or silica particles, with a systematic effect on the lungs causes diseases - pneumoconiosis. In the case of coal dust, this is an antrake-professional form of miners. When inhalation of dust containing Si02, silicosis occurs. The mechanism of development of pneumoconiosis has not yet been established. It is assumed that with long-term contact of silicate grains with biological fluids, polycreen acid Si02 YH2O is formed in a gel condition, whose deposition in cells leads to their death.

The toxic effect of lead is known to mankind for a long time. The use of lead for the manufacture of dishes and water pipes led to mass poisoning of people. Currently, the lead continues to be one of the main environmental pollutants, since the chief of lead compounds into the atmosphere is over 400,000 tons annually. Lead accumulates mainly in the skeleton in the form of a low-soluble phosphate RZ (P04) 2, and in the demineralization of bones, there is a regular toxic effect on the body. Therefore, lead refers to cumulative poisons. The toxicity of lead compounds is primarily connected with its complex-forming properties and greater affinity for biolygandam, especially containing sulfhydryl groups (-sh):

The formation of complex compounds of lead ions with proteins, phospholipids and nucleotides leads to their denaturation. Often, lead ions inhibit the metal components of EM 2+, displacing the cations of metals of life:

Lead and its compounds belong to poisons acting mainly on the nervous system, blood vessels and blood. In this case, lead compounds affect the synthesis of protein, the energy balance of cells and their genetic apparatus.

In medicine, as binding outer antiseptic agents are used: lead acetate PB (SNZSOO) 2 zn2o (lead grades) and lead (2) RBO oxide (lead plaster). The lead ions of these compounds react with proteins (albumin) of the cytoplasm of microbial cells and tissues, forming gel-like albuminates. The formation of gels kills microbes and, in addition, it makes it difficult to penetrate them into the tissue cells, which reduces the local inflammatory response.

(first electron)

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

History

Carbon In the form of charcoal, it was used in deep antiquity for the smelting of metals. Allotropic modifications of carbon-diamond and graphite are long known. The elementary nature of carbon is established by A. Lavoisier in the late 1780s.

origin of name

International name: Carbō - coal.

Physical properties

Carbon exists in a variety of allotropic modifications with very diverse physical properties. A variety of modifications is due to carbon ability 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 \u003d 5730), focused in the atmosphere and the upper part of the earth's crust. It is constantly formed in the lower layers of the stratosphere as a result of the effects of cosmic radiation neutrons on the nitrogen nucleus in the reaction: 14 N (N, P) 14 C, as well as from the mid-1950s, as a technogenic product of the NPP, and as a result of testing hydrogen bombs .

On the formation and decay of 14 seconds, the method of radiocarbon dating is based, widely used in quaternary geology and archeology.

Allotropic carbon modifications

The schemes of the structure of various carbon modifications
a.: diamond, b.: graphite, c.: Lonsdaleit
d.: Fullerene Buccol C 60, e.: Fullerene C 540, f.: Fullerene C 70
g.: amorphous carbon, h.: Carbon nanotube

Allhotropy carbon

lonsdaleit

fullerene

carbon nanotubes

amorphous carbon

Coal carbon Saleg

Electronic orbitals of carbon atom may have different geometry, depending on the degree of hybridization of its electronic orbitals. There are three basic geometry of carbon atom.

Tetrahedrician -it is formed when mixing of one S- and three p-electrons (SP 3-hybridization). The carbon atom is located in the center of the tetrahedron, is associated with four equivalent σ-bonds with carbon atoms or other in the vertices of the tetrahedron. Such geometry of the carbon atom corresponds to allotropic modifications of carbon diamond and lansdalet. Such hybridization has carbon, for example, in methane and other hydrocarbons.

Trigonal - It is formed when mixing one S- and two P-electronic orbitals (SPM-hybridization). The carbon atom has three equal σ-bonds located in one plane at an angle of 120 ° to each other. Not participating in the hybridization of the p-orbital, located perpendicular to the σ-bond planes, is used to form π-bond with other atoms. Such carbon geometry is characteristic of graphite, phenol, etc.

Digidal -it is formed when mixing one S and one p-electrons (SP-hybridization). At the same time, two electronic clouds are elongated along one direction and have the form of asymmetric dumbbells. Two other P-electrons give π-bonds. Carbon with such an atom geometry forms a special allotropic modification - carbin.

Graphite and diamond

Basic and well-studied crystalline modifications of carbon-diamond and graphite. Under normal conditions, thermodynamically stable only graphite, and diamond and other forms of metastable. At atmospheric pressure and temperatures above 1200 Kalmaz begins to move into graphite, above 2100, the KPR is performed in seconds. ΔH 0 transition - 1,898 kJ / mol. Under normal pressure, carbon is sublimated at 3780 K. Liquid carbon exists only at a certain external pressure. Triple points: graphite-liquid pairs T \u003d 4130 k, p \u003d 10.7 MPa. The direct transition of graphite in the diamond occurs at 3000 Ki pressure of 11-12 GPa.

With a pressure of more than 60 GPa, it is assumed to form a very dense modification with III (density by 15-20% higher than the density of the diamond) having a metallic conductivity. At high pressures and relatively low temperatures (approx. 1200 K), a hexagonal modification of carbon with a crystal lattice of type Wurcita-LonsDylit (A \u003d 0.252 nm, C \u003d 0.412 nm, spatial group P6 3 / TTS), 3,51 density g / cm³, that is, the same as the diamond. Lonsdaleit is also found in meteorites.

Ultradisperse diamonds (nanoalmas)

In the 1980s. In the USSR, it was found that in the conditions of dynamic loading of carbon-containing materials, diamond-like structures that were called ultrafine diamonds may be formed. Currently, the term "nanoalmas" is increasingly used. Particle size in such mothers is nanometers. The formation of the formation of the remote control can be implemented in the detonation of explosives with a significant negative oxygen balance, such as the mixtures of TNT with hexogen. Such conditions can also be implemented with the strikes of the celestial bodies about the surface of the Earth in the presence of carbon-containing materials (organic, peat, coal, etc.). So, in the fall zone of the Tungusian meteorite in the forest litter was discovered.

Karbin

Crystal modification of carbon black of hexagonal Singonia with a chain structure of molecules is called carbines. Chains have either a polyenic structure (-c≡c-), or polycumulative (\u003d C \u003d C \u003d). It is known several forms of carbine, characterized by the number of atoms in the elementary cell, cell sizes and density (2.68-3.30 g / cm³). Carbines occurs in nature in the form of a semiral semiral (white bodies and inclusions in graphite) and obtained by artificially oxidizing dehydropolization of acetylene, the action of laser radiation on graphite, from hydrocarbons or CCl 4 in low-temperature plasma.

Carbines is a small-crystalline black powder (density of 1.9-2 g / cm³), has semiconductor properties. Received in artificial conditions from long chains of atoms carbonlaid parallel to each other.

Carbon carbon linear polymer. In the carbon molecule, carbon atoms are connected to the chains alternately either triple and single bonds (polyenoval structure) or constantly double connections (polycumulative structure). This substance was first obtained by Soviet chemists V.V. Korshuk, A.M. Sladekov, V.I. Kasketkin and Yu.P. Kudryavtsev at the beginning of the 60s. in Institute of Elementorganic Compounds of the Academy of Sciences of the USSR . The carbine has semiconductor properties, and under the influence of light, its conductivity increases greatly. On this property, the first practical application is based on photocells.

Fullerenes and carbon nanotubes

Carbon is also known in the form of cluster particles with 60, C 70, C 80, C 90, C 100, and similar (fullerene), as well as graphene and nanotubes.

Amorphous carbon

The structure of the amorphous carbon is based on the disordered structure of the single crystal (always contains impurities) graphite. It is coke, brown and stone coals, carbon, soot, active coal.

Finding in nature

Carbon content in the earth's crust is 0.1% by weight. Free carbon is in nature in the form of diamond and graphite. The main mass of carbon in the form of natural carbonates (limestone and dolomites), combustible fossils - anthracite (94-97% C), brown coals (64-80% C), stone coals (76-95% C), combustible shale (56- 78% C), oil (82-87% C), combustible natural gases (up to 99% methane), peat (53-56% C), as well as bitumens, etc. In the atmosphere and hydrosphere is in the form of carbon dioxide CO 2 , in the air 0.046% CO 2 by weight, in the waters of rivers, seas and oceans at ~ 60 times more. Carbon is part of plants and animals (~ 18%).
In the human body, carbon comes with food (normally about 300 g per day). The total carbon content in the human body reaches about 21% (15kg at 70 kg body weight). Carbon is 2/3 masses of muscles and 1/3 of the mass of bone tissue. Excreted from the body mainly with exhaled air (carbon dioxide) and urine (urea)
The carbon circuit in nature includes a biological cycle, the release of CO 2 into the atmosphere during the combustion of fossil fuels, from volcanic gases, hot mineral sources, from surface layers of oceanic water, etc. The biological cycle is that carbon in the form of CO 2 is absorbed from the troposphere by plants . Then, from the biosphere again returned to the geopa: carbon plants fall into the organism of animals and humans, and then with the rotting of animals and plant materials, in 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, it 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 atoms with each other, the ability to form stable chains and cycles from atoms C causes the existence of a huge number of carbon-containing compounds studied by organic chemistry.

Chemical properties

At normal temperatures, carbon is chemically inert, with quite high connected with many elements, manifests strong rehabilitation properties. The chemical activity of various forms of carbon decreases in a row: amorphous carbon, graphite, diamond, in air they flamm down at temperatures, respectively, 300-500 ° C, 600-700 ° C and 850-1000 ° C.

The degree of oxidation is +4, -4, rarely +2 (CO, carbides of metals), +3 (C 2 N 2, halogencyanis); Electron affinity 1.27 eV; The energy of ionization with a sequential transition from C 0 to C 4+, respectively, 11,2604, 24.383, 47,871 and 64,19 eV.

Inorganic compounds

Carbon reacts with many elements with the formation of carbides.

CO carbon monoxide combustion products and carbon dioxide CO 2. Also known is also known oxide with 3 o 2 (melting point -111 ° C, boiling point 7 ° C) and some other oxides. Graphite and amorphous carbon begin to react with H 2 at 1200 ° C, with F 2 - respectively 900 ° C.

CO 2 with water forms weak coalic acid, H 2 CO 3, which forms solidarbones. Calcium carbonates (chalk, marble, calcite, limestone, etc. Minerals) and magnesium (dolomite) are most widely distributed on Earth.

Graphite with halogens, alkaline metals, etc. substances forms inclusion connections. When the electrical discharge between coal electrodes in medium N 2, a cyan is formed, at high temperatures with carbon reaction with a mixture H 2 and N 2, a sinyl acid is obtained. With gray carbon gives CS 2 servo carbon, CS and C 3 S 2 are also known. With most metals, boron and silicon carbon forms carbides. It is important in the industry of carbon reaction with water vapor: C + H 2 O \u003d CO + H 2 (gasification of solid fuels). When heated, carbon restores metal oxides to metals, which is widely used in metallurgy.

Organic compounds

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

Carbon compounds make up the basis of the earth's life, and their properties largely determine the range of conditions in which such forms of life may exist. According to the number of atoms in living cells, carbon fraction is about 25%, by the mass fraction of about 18%.

Application

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

Diamond due to exceptional hardness, indispensable abrasive material. Diamond spraying have grinding nozzles Borminhin. In addition, the faceted diamonds - diamonds are used as precious stones in jewelry. Due to the rarity, high decorative qualities and coating of historical circumstances, the diamond is invariably the most expensive gem. An exceptionally high thermal conductivity of diamond (up to 2000 W / mk) makes it a promising material for semiconductor equipment as substrates for processors. But the relatively high price (about 50 dollars / grams) and the complexity of diamond treatment limit its use in this area.
In pharmacology and medicine, various compounds of carbon-derivatives of coalic acid and carboxylic acids, various heterocycles, polymers and other connections are widely used. So, carricul (activated carbon) is used for absorption and removal from the body of various toxins; graphite (in the form of ointments) - for the treatment of skin diseases; Radioactive carbon isotopes - for scientific research (radiocarbon analysis).

Carbon plays a huge role in human life. Its applications are as diverse as this multi-cable element itself.

Carbon is the basis of all organic substances. Any living organism is largely made of carbon. Carbon is the basis of life. The source of carbon for living organisms is usually CO 2 of the atmosphere or water. As a result of photosynthesis, it enters biological food chains in which living beings devour each other or the remains of each other and thus mining carbon for the construction of their own body. The biological carbon cycle ends either by oxidation and return to the atmosphere, or the burial in the form of coal or oil.

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

Toxic action

Carbon is part of atmospheric aerosols, as a result of which the regional climate can change, the number of sunny days will decrease. Carbon enters the surrounding medium in the form of a hydrofluorine exhaust gas composition, when burning coal on TPPs, with open developments of coal, underground gasification, obtaining coal concentrates, and other carbon concentration over combustion sources 100-400 μg / m³, major cities 2, 4-15.9 μg / m³, rural areas of 0.5-0.8 μg / m³. With gas-aerosol emissions of nuclear power plants, (6-15) .10 9 BK / SUT 14 CO 2 enters the atmosphere.

The high carbon content in atmospheric aerosols leads to an increase in the incidence of the population, especially the upper respiratory tract and lungs. Professional diseases - mainly antrakes and dust bronchitis. In the air of the working area of \u200b\u200bthe MPC, mg / m³: diamond 8.0, anthracite and coke 6,0, stone coal 10.0, technical carbon and carbon dust 4.0; In atmospheric air, the maximum one-time 0.15, the average daily 0.05 mg / m³.

The toxic effect 14 C, which became part of the protein molecules (especially in DNA and RNA), is determined by the radiation effect of the beta of particles and nitrogen recoil nuclei (14 C (β) → 14 n) and the transmutation effect of the chemical composition of the molecule as a result of the conversion of an atom with to atom n. permissible concentration of 14 s in the air of the working area of \u200b\u200bDK A 1.3 BK / L, in atmospheric air DK b 4.4 BK / L, in water 3.0.10 4 BK / L, maximum allowable admission through respiratory organs 3 , 2.10 8 BC / year.

Additional Information

- Carbon compounds
- Radio carbon analysis
- Ortocarboan Acid

Allotropic carbon forms:

Diamond
Graphen
Graphite
Karbin
Lonsdaleit
Carbon nanotubes
Fullerene

Amorphous forms:

Soot
Technical carbon
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 a day): 15c: carbon-15, 16c: carbon-16, 17c: carbon-17, 18c: carbon-18, 19c: carbon-19, 20c: carbon-20, 21c: carbon-21, 22c: Carbon-22.

Table nuclides

Carbon, Carboneum, C (6)
Carbon (eng. Carbon, Franz. Carbone, it. Kohlenstoff) in the form of coal, soot and soot are known to humanity from time immemorial; About 100 thousand years ago, when our ancestors captured fire, they were daily dealing with coal and soot. Probably, very early people became acquainted with allotropic carbon modes - diamond and graphite, as well as fossil coal. It is not surprising that the burning of carbon-containing substances was one of the first chemical processes interested in a person. Since the burning substance disappeared, devoured by fire, the burning was considered as the process of decomposition of the substance, and therefore coal (or carbon) were not considered an element. The element was a fire - a phenomenon accompanying combustion; In the exercises on elements of antiquity, the fire typically appears as one of the elements. At the turn of the XVII - XVIII centuries. A phlogiston theory extended beheads and a panel arose. This theory recognized the presence of a special elementary substance in each combustible body - the weightless fluid - phlogiston, catering in the process of burning.

When combustion of a large amount of coal, only some ash remains, the flogistic believed that coal was almost pure phlogiston. This was explained, in particular, the "Flogisting" action of coal - its ability to restore metals from the "ryime" and ore. Latest Flogistics, Reomyur, Bergman, and others, have already begun to understand that the coal is an elementary substance. However, for the first time, a "pure coal" was recognized by Lavoisier, which studied the combustion process in the air and oxygen of coal and other substances. In the book of Hiton de Morso, Lavoisier, Bertolls and Furkrua "Method of Chemical Nomenclature" (1787) appeared the name "Carbon" (carbone) instead of the French "Clean Coal" (Charbone Pur). Under the same name, carbon appears in the "table of simple bodies" in the "elementary textbook of chemistry" Lavoisier. In 1791, the English Chemist Tennant was first received free carbon; He missed the phosphorus pair over the calcined chalk, as a result of which the calcium phosphate and carbon was formed. The fact that diamond is burning with strong heating without a balance, it has been known for a long time. Back in 1751, the French king Franz I agreed to give Diamond and Rubin for burning experiments, after which these experiments even became fashionable. It turned out that only diamond burns, and ruby \u200b\u200b(aluminum oxide with chromium admissions) withstands prolonged heating in the focus of the incendiary lens. Lavoisier has put a new diamond burning experience with a large incendiary machine, concluded that the diamond is crystalline carbon. The second altotrope of carbon - graphite in the alochemical period was considered a modified lead glitter and was called Plumbago; Only in 1740 Pott found the lack of lead in graphite any impurity. The Shelele explored graphite (1779) and being Flocistry found it with a sulfur body of a special kind, special mineral coal containing the associated "aircraft" (CO2,) and a large amount of phlogiston.

Twenty years later, Hyton de Morvo by cautious heating turned diamond to graphite, and then into coalic acid.

The international name Carboneum comes from Lat. CARBO (coal). The word is very ancient origin. It is compared with Cremare - burn; Root Sag, Cal, Russian Gar, Gal, Goal, Sanskrit Stowe means boiling, cook. With the word "carbo" are related to the names of carbon and in other European languages \u200b\u200b(Carbon, Charbone, etc.). German Kohlenstoff comes from Kohle - coal (Starogerman Kolo, Swedish Kylla - heated). Ancient Russian refinery, or Ugrati (burn, beaten) has a root of gar, or mountains, with a possible transition to the goal; Coal in Old Russian Yugil, or coal, the same origin. The word Almaz (Diamante) comes from ancient Greek - disadvantageous, adamant, solid, and graphite from Greek - I write.

At the beginning of the XIX century. The old word coal in Russian chemical literature was sometimes replaced by the word "home" (Sherler, 1807; Severgine, 1815); From 1824, Solovyov introduced the name carbon.