A covalent chemical bond is a type of bond due to which molecules of inorganic and organic substances are formed. A chemical bond appears due to the interaction of electric fields that are created by the nuclei and electrons of atoms. Consequently, the formation of a covalent chemical bond is associated with electrical nature.
What is a connection?
By this term is meant the result of the action of two or more atoms, which lead to the formation of a strong polyatomic system. The main types of chemical bonds are formed when the energy of reacting atoms decreases. In the process of bond formation, atoms try to complete their electronic shell.
Types of communication
In chemistry, several types of bonds are distinguished: ionic, covalent, metal. The covalent chemical bond has two varieties: polar, non-polar.
What is the mechanism of its creation? A covalent non-polar chemical bond is formed between atoms of the same non-metals having the same electronegativity. In this case, common electronic pairs are formed.
Non-polar communication
Among examples of molecules in which a covalent chemical bond is non-polar, halogens, hydrogen, nitrogen, oxygen can be mentioned.
This relationship was first discovered in 1916 by the American chemist Lewis. At first he put forward a hypothesis, and it was confirmed only after experimental confirmation.
A covalent chemical bond is associated with electronegativity. In non-metals, it is of high importance. During the chemical interaction of atoms, the transfer of electrons from one atom to another is not always possible; as a result, they combine. A genuine covalent chemical bond appears between the atoms. Grade 8 of the regular school curriculum involves a detailed examination of several types of communication.
Substances having this type of bond under normal conditions are liquids, gases, and also solids having a low melting point.
Types of covalent bond
Let us dwell on this issue in more detail. What types of chemical bonds are distinguished? Covalent bond exists in the exchange, donor-acceptor variants.
The first type is characterized by the return by each atom of one unpaired electron to the formation of a common electronic bond.
Electrons combined into a common bond must have opposite spins. As an example of this type of covalent bond, we can consider hydrogen. When its atoms come closer together, their electron clouds penetrate each other, called in science the overlapping of electronic clouds. As a result, the electron density between the nuclei increases, and the energy of the system decreases.
At a minimum distance, the hydrogen nuclei repel, as a result, a certain optimal distance is formed.
In the case of a donor-acceptor type of covalent bond, one particle has electrons, it is called a donor. The second particle has a free cell in which a pair of electrons will be placed.
Polar molecules
How are covalent polar chemical bonds formed? They arise in those situations when the bonded non-metal atoms have different electronegativity. In such cases, socialized electrons are placed closer to the atom whose electronegativity is higher. As an example of a covalent polar bond, bonds that arise in a hydrogen bromide molecule can be considered. Here, the social electrons that are responsible for the formation of the covalent bond are closer to bromine than to hydrogen. The reason for this is that bromine has a higher electronegativity than hydrogen.
Methods for determining covalent bond
How to determine covalent polar chemical bonds? To do this, you need to know the composition of the molecules. If atoms of different elements are present in it, a covalent polar bond exists in the molecule. In nonpolar molecules, atoms of the same chemical element are present. Among the tasks that are offered as part of the school chemistry course, there are those that involve identifying the type of connection. Tasks of this type are included in the tasks of the final certification in chemistry in the 9th grade, as well as in the tests of the unified state exam in chemistry in the 11th grade.
Ionic bond
What is the difference between covalent and ionic chemical bonds? If a covalent bond is characteristic of nonmetals, then an ionic bond is formed between atoms having significant differences in electronegativity. For example, this is typical for compounds of elements of the first and second groups of the main subgroups of PS (alkaline and alkaline earth metals) and elements of 6 and 7 groups of the main subgroups of the periodic table (chalcogenes and halogens).
It is formed as a result of electrostatic attraction of ions with opposite charges.
Features of ionic bonding
Since the force fields of oppositely charged ions are distributed uniformly in all directions, each of them is able to attract particles of opposite sign. This characterizes the non-directivity of the ionic bond.
The interaction of two ions with opposite signs does not imply a complete mutual compensation of individual force fields. This helps to maintain the ability to attract ions in other directions, therefore, there is an unsaturation of the ionic bond.
In an ionic compound, each ion has the ability to attract a certain number of others with opposite signs to form an ionic crystal lattice. There are no molecules in such a crystal. Each ion is surrounded in matter by a specific number of ions of a different sign.
Metal bond
This type of chemical bond has certain individual characteristics. Metals have an excess of valence orbitals with a lack of electrons.
When individual atoms approach each other, their valence orbitals overlap, which contributes to the free movement of electrons from one orbital to another, making a bond between all metal atoms. These free electrons are the main sign of metallic bonding. It does not possess saturation and directivity, since valence electrons are uniformly distributed throughout the crystal. The presence of free electrons in metals explains their certain physical properties: metallic sheen, ductility, ductility, thermal conductivity, opacity.
A kind of covalent bond
It is formed between the hydrogen atom and the element, which has a high electronegativity. There are intra- and intermolecular hydrogen bonds. This kind of covalent bond is the most fragile, it appears due to the action of electrostatic forces. The hydrogen atom has a small radius, and when this one electron is displaced or transferred, hydrogen becomes a positive ion acting on the atom with great electronegativity.
Among the characteristic properties of a covalent bond are: saturation, directivity, polarizability, polarity. Each of these indicators has a specific value for the formed compound. For example, directivity is determined by the geometric shape of the molecule.