Carbon. Characteristics, properties and application

Carbon is a chemical element, a non-metal. Its properties depend on the variety in which it occurs. It is in fourth place in the elements found in the universe, after oxygen, hydrogen and helium. It is present in every living organism. In the human body, after oxygen, it is the most abundant element in terms of mass. This amount, combined with the variety of organic compounds, makes carbon the basis of life.

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1. What is coal?

Carbon - C (Latin carboneum) is a non-metal chemical element with an atomic number of 6. In the periodic table of elements, it is in the p block, in group 14 (IVA). It has 4 valence electrons. There are 3 natural isotopes of carbon. 12C and 13C are stable while the 14C isotope is radioactive. Its half-life is approximately 5700 years.

It was known as one of the few elements in prehistoric times. Fossil coal has been used as fuel since the 9th century. In ancient times, graphite and diamond were also known, but it was not realized then that they were allotropic types of carbon (more on this later in the text).

In 1773, the French physicist Antoine Lavoisier burned a diamond in oxygen, which gave him carbon dioxide. In 1779, the German-Swedish chemist apothecary Carl Scheele stated the same for graphite. The Polish name was first proposed by the Polish chemist, Filip Neriusz Walter.

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2. Allotropic varieties of coal

Carbon comes in the following allotropic varieties:

  • fullerene;
  • Diamond;
  • graphite;
  • graphene;
  • cyclocarbon.

We also distinguish nanobubbles and nanotubes, which are not entirely allotropes of carbon - they are rather names of supramolecular structures. According to unconfirmed reports, we can also talk about the existence of carbine and linear chains.

3. Chemical properties of coal

Carbon is a divalent and tetravalent element in the oxidation states +2, +4 and -4. This element is chemically inactive, it is not soluble in water, bases and acids. At a temperature of about 20 ° C it only reacts with fluorine.

When heated, carbon reacts with sulfur and oxygen, and at very high temperatures it directly combines with hydrogen and many atoms to form so-called carbides.

Carbon atoms have the ability to bond with each other, thanks to which there are a very large number of carbon compounds, ring and chain, branched and straight. Apart from carbon, these compounds include nitrogen, oxygen, sulfur and halogens.

One of the allotropic types of carbon - diamond is a substance with low activity, even at high temperatures. It burns slowly in air (over 800 ° C), while in pure oxygen it burns more rapidly. Neither acids nor bases work on a diamond.

Another allotropic form of carbon - graphite is a substance with also low activity, but it reacts more easily than diamond. In air, graphite burns at a temperature of about 700 ° C. Reacts with fluorine in the presence of hydrogen fluoride (HF) at temperatures below 100 ° C, without HF at temperatures above 400 ° C.

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4. Physical properties and application

Carbon is a solid. It dissolves in molten iron or some other molten metals, but does not dissolve in any known solvent.

Coal does not melt, but sublimes under atmospheric pressure and at very high temperatures over 3500 ° C. As we have already described, it occurs in two basic allotropes (diamond and graphite), differing in their crystallographic form. Amorphous carbon (soot) is a fine-crystalline form of graphite.

4.1. Diamond

In its pure state, the diamond creates transparent, colorless structures. It is characterized by high hardness (it is the hardest among all minerals), it breaks light strongly and is an insulator (it does not conduct electricity).

The diamond has a density of 3.51 g / cm³. In the spatial lattice of a diamond, all carbon atoms are surrounded by 4 other atoms, some of the centers of gravity are defined by the regular tetrahedron.

Each chemical bond in the diamond lattice is a covalent bond of equal length. Depending on the amount and type of impurities, diamond crystals may be red, yellow, blue, purple and brown in color.

Cut diamonds are diamonds, their characteristic feature is a wonderful play of light. A diamond that is suitable for jewelery purposes is quite rare. First of all, diamond mining is used for technical purposes.

It is used to grind extremely hard bodies, make blades for mining drills, cut glass, and create bearings in precision instruments.

Heating the diamond in the absence of air at a temperature above 1500 ° C leads to the production of graphite. Reversing this reaction and converting graphite to diamond is a difficult operation.

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4.2. Graphite

The second basic allotropic form of carbon is graphite, also present as a mineral. It is black-and-gray, it is greasy and soft to the touch. It has a faint metallic luster, conducts heat and electricity well, and has a density of 2.1 to 2.3 g / cm³.

The spatial network of this mineral consists of parallel layers in which the carbon atoms have a coordination number of 3. Strong atomic bonds take place only between the carbon atoms in the layer, and between the layers, these bonds are weaker.

Graphite and fine clay additives as a binding agent are used in the production of metal melting crucibles. Since graphite conducts electricity well, it is used to make electrodes for the electro-metallurgical and chemical industries.

It is also used for the production of pencils, graphite in the form of a suspension in machine oil is used as a lubricant for mechanisms operating at high temperatures or as a moderator in atomic stacks.

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4.3. Amorphous carbon

Amorphous carbon is produced by the thermal decomposition of many organic substances. The properties of this type of coal (coke, soot, charcoal and bone coal) largely depend on the starting product and the temperature at which the decomposition was carried out.

We obtain coke in the process of dry distillation (heating without oxygen) of hard coal at a temperature of 1000 - 1200 ° C. It is used primarily as a fuel, as well as in the synthesis of organic compounds on an industrial scale.

Carbon black is a product of the thermal decomposition of many hydrocarbons and the incomplete combustion of various organic substances. It is used for the production of ink, painting and printing paints and for filling rubber.

We obtain charcoal as a product of the above-mentioned dry distillation. It has good adsorption properties.

As a result of charcoal carbonization at the lowest possible temperatures with the addition of ZnCl2, we obtain active carbon with a well-developed surface. It is used to absorb gases or substances dissolved in solutions (decolorization of solvents and preparations, drying of gases, purification of air from vapors). It can also be used as a catalyst carrier in organic synthesis.

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