Carbon is ... A carbon atom. Mass of carbon

One of the most amazing elements that can form a huge number of various compounds of organic and inorganic nature is carbon. This element is so unusual in its properties that even Mendeleev predicted a great future for him, speaking of features not yet revealed.

This was later confirmed practically. It became known that he is the main biogenic element of our planet, which is part of absolutely all living creatures. In addition, it can exist in such forms that radically differ in all parameters, but at the same time consist only of carbon atoms.

In general, this structure has many features, and we will try to deal with them in the course of the article.

Carbon: formula and position in the system of elements

In the periodic system, the carbon element is located in the IV (according to a new sample in 14) group, the main subgroup. Its serial number is 6, and its atomic weight is 12.011. The designation of the element with the C sign indicates its name in Latin - carboneum. There are several different forms in which carbon exists. Therefore, its formula is different and depends on the specific modification.

However, for writing reaction equations, there is, of course, a concrete notation. In general, when talking about a substance in its pure form, the molecular formula of carbon C is adopted, without indexation.

Item Discovery History

In itself, this element has been known since antiquity. After all, one of the most important minerals in nature is coal. Therefore, for the ancient Greeks, Romans and other nationalities, it was not a secret.

In addition to this variety, diamonds and graphite were also used. There have been many complicated situations with the latter for a long time, since often without analysis of the composition such compounds were taken for graphite as:

• silver lead;
• iron carbide;
• molybdenum sulfide.

All of them were painted black and therefore were considered graphite. This misunderstanding was later clarified, and this form of carbon became itself.

Since 1725, diamonds have gained great commercial importance, and in 1970 the technology for producing them artificially was mastered. Since 1779, thanks to the work of Karl Scheele, the chemical properties of carbon are being studied. This served as the beginning of a number of important discoveries in the field of this element and became the basis for elucidating all its unique features.

Carbon isotopes and distribution in nature

Despite the fact that the element under consideration is one of the most important biogenic, its total content in the mass of the earth's crust is 0.15%. This is due to the fact that it undergoes constant circulation, a natural cycle in nature.

In general, there are several compounds of a mineral nature, which include carbon. These are natural breeds such as:

• dolomites and limestones;
• anthracite;
• oil shale;
• natural gas;
• coal;
• oil;
• brown coal;
• peat;
• bitumen.

In addition, one should not forget about living things, which are just a repository of carbon compounds. After all, he formed proteins, fats, carbohydrates, nucleic acids, which means the most vital structural molecules. In general, for the recalculation of dry body weight of 70 kg, 15 falls on a pure element. And so with every person, not to mention animals, plants and other creatures.

If we consider the composition of air and water, that is, the hydrosphere as a whole and the atmosphere, then there is a carbon-oxygen mixture expressed by the formula CO ₂ . Dioxide or carbon dioxide is one of the main gases that make up air. It is in this form that the mass fraction of carbon is 0.046%. Carbon dioxide is even more dissolved in the waters of the oceans.

The atomic mass of carbon as an element is 12.011. It is known that this value is calculated as the arithmetic mean between the atomic weights of all isotopic species existing in nature, taking into account their prevalence (in percentage terms). This happens with the substance in question. There are three main isotopes in which carbon is located. It:

• ¹² - its mass fraction in the vast majority is 98.93%;
• ¹³ C - 1.07%;
• ¹⁴ C - radioactive, half-life of 5700 years, stable beta-emitter.

In the practice of determining the geochronological age of samples, the radioactive isotope ¹⁴ C is widely used, which is an indicator due to its long decay period.

Allotropic modifications of an element

Carbon is an element that, in the form of a simple substance, exists in several forms. That is, he is able to form the largest of the number of allotropic modifications known to date.

1. Crystal variations - exist in the form of strong structures with regular atomic-type lattices. This group includes such varieties as:

• diamonds
• fullerenes;
• graphites;
• carbines;
• lonsdaleite;
• carbon fibers and tubes.

All of them differ in the structure of the crystal lattice, in the nodes of which there is a carbon atom. Hence completely unique, dissimilar properties, both physical and chemical.

2. Amorphous forms - they form a carbon atom, which is part of some natural compounds. That is, these are not pure varieties, but with impurities of other elements in small quantities. This group includes:

• Activated carbon;
• stone and wood;
• soot;
• carbon nanofoam;
• anthracite;
• glassy carbon;
• technical type of substance.

They are also united by structural features of the crystal lattice, explaining and manifesting properties.

3. Carbon compounds in the form of clusters. Such a structure, in which atoms are closed into a special hollow conformation from the inside, filled with water or the nuclei of other elements. Examples:

• carbon nanocones;
• astral;
• diocarbon.

Physical properties of amorphous carbon

Due to the wide variety of allotropic modifications, it is difficult to isolate some common physical properties for carbon. It's easier to talk about a specific form. So, for example, amorphous carbon has the following characteristics.

1. At the heart of all forms are crystalline varieties of graphite.
2. High heat capacity.
3. Good conductor properties.
4. The density of carbon is about 2 g / cm ³ .
5. When heated above 1600 ⁰ C, a transition to graphite forms occurs.

Soot, charcoal and stone varieties are widely used for technical purposes. They are not a manifestation of carbon modification in its pure form, but contain it in very large quantities.

Crystalline carbon

There are several options in which carbon is a substance that forms regular crystals of various kinds, where atoms are connected in series. As a result, the following modifications are formed.

1. Diamond. The structure is cubic, in which four tetrahedra are connected. As a result, all covalent chemical bonds of each atom are as saturated and strong as possible. This explains the physical properties: carbon density 3300 kg / m ³ . High hardness, low heat capacity, lack of electrical conductivity - all this is the result of the structure of the crystal lattice. There are technically obtained diamonds. They are formed during the transition of graphite to the next modification under the influence of high temperature and a certain pressure. In general, the melting point of diamond is as high as the strength - about 3500 ⁰ C.
2. Graphite. Atoms are located similar to the structure of the previous substance, however, only three bonds are saturated, and the fourth becomes longer and less strong, it connects the “layers” of the hexagonal lattice rings. As a result, it turns out that graphite is a soft, greasy to the touch substance of black color. It has good electrical conductivity and has a high melting point - 3525 ⁰ C. It is capable of sublimation - sublimation from solid to gaseous, bypassing the liquid (at a temperature of 3700 ⁰ C). The carbon density is 2.26 g / cm ^3, which is much lower than that of diamond. This explains their various properties. Due to the layered structure of the crystal lattice, it is possible to use graphite for the manufacture of lead pencils. When held on paper, the flakes peel off and leave a black mark on the paper.
3. Fullerenes. They were discovered only in the 80s of the last century. They are modifications in which the carbons are connected to each other in a special convex closed structure with a void in the center. Moreover, the shape of the crystal is a polyhedron, of proper organization. The number of atoms is even. The most famous form of fullerene is C ₆₀ . Samples of a similar substance were found in studies:

• meteorites;
• bottom sediments;
• folgurites;
• shungite;
• outer space, where they were contained in the form of gases.

All varieties of crystalline carbon are of great practical importance because they have a number of properties useful in the technique.

Chemical activity

Molecular carbon exhibits low chemical activity due to its stable configuration. It is possible to force him to enter into reactions only by informing the atom of additional energy and forcing the electrons of the external level to vaporize. At this moment, the valency becomes 4. Therefore, in compounds it has an oxidation state of + 2, + 4, - 4.

Almost all reactions with simple substances, both metals and non-metals, occur under the influence of high temperatures. The element in question can be either an oxidizing agent or a reducing agent. However, the latter properties are especially pronounced in him, it is precisely on this that his application in the metallurgical and other industries is based.

In general, the ability to enter into a chemical interaction depends on three factors:

• dispersion of carbon;
• allotropic modification;
• reaction temperature.

Thus, in some cases, interaction occurs with the following substances:

• non-metals (hydrogen, oxygen);
• metals (aluminum, iron, calcium and others);
• metal oxides and their salts.

It does not react with acids and alkalis, very rarely with halogens. The most important of the properties of carbon is the ability to form long chains between themselves. They can lock into a cycle, form branches. This is the formation of organic compounds, which today amount to millions. The basis of these compounds are two elements - carbon, hydrogen. Also, other atoms can be included in the composition: oxygen, nitrogen, sulfur, halogens, phosphorus, metals and others.

The main compounds and their characteristics

There are many different compounds that include carbon. The formula of the most famous of them is CO ₂ - carbon dioxide. However, in addition to this oxide, there is also CO - monoxide or carbon monoxide, as well as C ₃ O ₂ underoxide.

Among the salts that make up this element, the most common are calcium and magnesium carbonates. So, calcium carbonate has several synonyms in the name, since it is found in nature in the form:

• chalk;
• marble;
• limestone;
• dolomite.

The importance of alkaline earth metal carbonates is manifested in the fact that they are active participants in the formation of stalactites and stalagmites, as well as groundwater.

Carbonic acid is another compound that forms carbon. Its formula is H ₂ CO ₃ . However, in its ordinary form, it is extremely unstable and immediately decomposes in solution into carbon dioxide and water. Therefore, only its salts are known, and not itself, as a solution.

Carbon halides - obtained mainly in an indirect way, since direct syntheses occur only at very high temperatures and with a low yield of product. One of the most common is CCL ₄ - carbon tetrachloride. A poisonous compound that can cause poisoning if inhaled. Obtained by radical photochemical substitution reactions of hydrogen atoms in methane.

Metal carbides are carbon compounds in which it exhibits an oxidation state of 4. It is also possible to combine with boron and silicon. The main property of carbides of some metals (aluminum, tungsten, titanium, niobium, tantalum, hafnium) is its high strength and excellent electrical conductivity. Boron carbide B ₄ C is one of the hardest substances after diamond (9.5 Mohs). These compounds are used in engineering as well as in the chemical industry as sources for producing hydrocarbons (calcium carbide with water leads to the formation of acetylene and calcium hydroxide).

Many metal alloys are made using carbon, thereby significantly improving their quality and technical characteristics (steel - an alloy of iron with carbon).

Numerous organic carbon compounds deserve special attention, in which it is a fundamental element capable of connecting with the same atoms into long chains of various structures. These include:

• alkanes;
• alkenes;
• arenas;
• proteins;
• carbohydrates;
• nucleic acids;
• alcohols;
• carboxylic acids and many other classes of substances.

Carbon application

The importance of carbon compounds and its allotropic modifications in human life is very great. You can name a few of the most global industries, so that it becomes clear that this is indeed so.

1. This element forms all types of fossil fuels, from which a person receives energy.
2. The metallurgical industry uses carbon as the strongest reducing agent to produce metals from their compounds. Carbonates are also widely used here.
3. The construction and chemical industries consume a huge amount of carbon compounds to synthesize new substances and produce the necessary products.

You can also name such industries as:

• nuclear industry;
• jewelry making;
• technical equipment (lubricants, heat-resistant crucibles, pencils, etc.);
• determination of the geological age of the rocks - a radioactive indicator of ¹⁴ C;
• carbon is an excellent adsorbent, which allows it to be used for the manufacture of filters.

The cycle in nature

The mass of carbon in nature is included in the constant cycle, which cyclically takes place every second across the globe. So, the atmospheric carbon source - CO ₂ , is absorbed by plants and secreted by all living things in the process of respiration. Once in the atmosphere, it is absorbed again, and so the cycle does not stop. At the same time, the death of organic residues leads to the release of carbon and its accumulation in the earth, from where it is then absorbed again by living organisms and released into the atmosphere in the form of gas.