The carbon atom: structure, features and properties
In this article, we consider an element that is part of the periodic table D.I. Mendeleev, namely carbon. In the modern nomenclature, it is denoted by the symbol C, is in the fourteenth group and is the "participant" of the second period, has a sixth sequence number, and its amu. = 12.0107.
Atomic orbitals and their hybridization
Let's start looking at carbon from its orbitals and their hybridization - its main features, thanks to which it makes scientists of the whole world to this day. What is their structure?
The hybridization of the carbon atom is arranged in such a way that the valence electrons occupy positions on three orbitals, namely: one is on the 2s orbitals, and two is on 2p-orbitals. The last two of the three orbitals form an angle equal to 90 degrees relative to each other, and the 2s orbital has spherical symmetry. However, this form of the device of the considered orbitals does not allow us to understand why carbon, entering into organic compounds, forms angles of 120, 180 and 109.5 degrees.The formula for the electronic structure of a carbon atom expresses itself as follows: (He) 2s22p2.
The resolution of the resulting contradiction was made by introducing the concept of hybridization of atomic orbitals. To understand the trihedral, variant nature of C, it was necessary to create three forms of understanding of its hybridization. The main contribution to the emergence and development of this concept was made by Linus Pauling.
The structure of the carbon atom determines the presence of a number of certain features of a physical nature. The atoms of this element form a simple substance - carbon, which has modifications. Variations in the changes in its structure can give the formed substance different quality characteristics. The reason for the presence of a large number of carbon modifications lies in its ability to establish and form heterogeneous bonds of chemical nature.
The structure of the carbon atom can vary, which allows it to have a certain number of isotopic forms. Carbon found in nature is formed by two isotopes in a stable state -12C and13C - and isotope with radioactive properties -14FROM.The last isotope is concentrated in the upper layers of the Earth’s crust and in the atmosphere. Due to the influence of cosmic radiation, namely its neutrons, on the nucleus of nitrogen atoms, a radioactive isotope is formed14C. After the mid-fifties of the twentieth century, it began to enter the environment as a technogenic product formed during the operation of nuclear power plants, and as a result of the use of a hydrogen bomb. It is on the decay process14C is the basis for radiocarbon dating, which has found its wide application in archeology and geology.
Modification of carbon in allotropic form
In nature, there are many substances that include carbon. Man uses the structure of the carbon atom for his own purposes when creating various substances, including:
- Crystal carbons (diamonds, carbon nanotubes, fibers and wires, fullerenes, etc.).
- Amorphous carbons (activated and charcoal, various types of coke, carbon black, soot, nanofoam and anthracite).
- Cluster forms of carbon (diggars, nanocones, and astralene compounds).
Structural features of the atomic structure
The electronic structure of a carbon atom may have a different geometry, which depends on the level of hybridization of the orbitals it possesses. There are 3 main types of geometry:
- Tetrahedral - is created due to the displacement of four electrons, one of which is s-, and three belong to p-electrons. Atom C occupies a central position in the tetrahedron, is connected by four equivalent sigma bonds with other atoms occupying the top of the given tetrahedron. With such a geometrical arrangement of carbon, its allotropic forms can form, for example, diamond and lonsdaleite.
- Trigonal - owes its appearance to the displacement of three orbitals, of which one is s- and two p-. Here there are three sigma bonds that are in equal position with each other; they lie in a common plane and adhere to an angle of 120 degrees with respect to each other. The free p-orbital is located perpendicular to the sigma-bond plane. Graphite has a similar geometry.
- Diagonal - appears due to the mixing of s-and p-electrons (sp hybridization). The electron clouds are drawn out along the general direction and take the form of an asymmetrical dumbbell. Free electrons create π-bonds.This structure of geometry in carbon gives rise to the appearance of carbyne, a special form of modification.
Carbon atoms in nature
The structure and properties of the carbon atom have long been considered by man and are used to obtain a large number of various substances. The atoms of this element, due to their unique ability to form different chemical bonds and the presence of hybridization of orbitals, create many different allotropic modifications with the participation of only one element, from atoms of one type, carbon.
In nature, carbon is found in the earth's crust; It takes the form of diamonds, graphites, various combustible natural resources, for example, oil, anthracite, brown coal, shale, peat, etc. Included in the gases used by man in the energy industry. The carbon in the composition of its dioxide fills the hydrosphere and the atmosphere of the Earth, and in the air it reaches 0.046%, and in the water - up to sixty times more.
In the human body, C is contained in an amount approximately equal to 21%, and it is mainly excreted in the urine and exhaled air. The same element is involved in the biological cycle, it is absorbed by plants and consumed during photosynthesis.
Carbon atoms, due to their ability to establish various covalent bonds and build chains of them, and even cycles, can create a huge amount of substances of organic nature. In addition, this element is part of the solar atmosphere, being in compounds with hydrogen and nitrogen.
Now consider the structure and properties of the carbon atom from a chemical point of view.
It is important to know that carbon exhibits inert properties under normal temperature conditions, but may show us properties of a reducing nature under the influence of high temperatures. Basic oxidation states: + - 4, sometimes +2, and also +3.
Participates in the reaction with a large number of elements. It can react with water, hydrogen, halogens, alkali metals, acids, fluorine, sulfur, etc.
The structure of the carbon atom generates an incredibly huge amount of substances separated into a separate class. Such compounds are called organic and are based on C. It is possible due to the property of the atoms of this element to form polymer chains. Among the most famous and extensive groups are proteins (proteins), fats, carbohydrates and hydrocarbon compounds.
Due to the unique structure of the carbon atom and its attendant properties, the element is widely used by man, for example, when creating pencils, smelting metal crucibles - graphite is used here. Diamonds are used as abrasive materials, jewelry, nozzles for drills, etc.
Pharmacology and medicine are also involved in the use of carbon in a variety of compounds. This element is part of the steel, serves as the basis for each organic substance, participates in the process of photosynthesis, etc.
The structure of the atom of the carbon element encompasses the presence of a dangerous effect on living matter. Carbon enters the world around us as a result of coal combustion at thermal power plants, is part of the gases produced by automobiles, in the case of coal concentrate, etc.
A high percentage of carbon in aerosols, which entails an increase in the percentage of morbidity in humans. The upper airways and lungs are most commonly affected. Some diseases can be classified as professional, for example, dust bronchitis and diseases of the pneumoconiosis group.
14C is toxic, and the strength of its influence is determined by the radiative interaction with β particles. This atom is part of the composition of biological molecules, including those contained in deoxy and ribonucleic acids. Permissible amount14C in the air of the working area is considered a mark of 1.3 Bq / l. The maximum amount of carbon entering the body during respiration is equal to 3.2 * 108Bq / year