Covalent bonding

For the first time about such a concept as a covalent bond , chemists began to talk after the discovery of Gilbert Newton Lewis, who described the chemical bond as the socialization of two electrons. More recent studies have made it possible to describe the very principle of covalent bonding. The word covalent can be considered in the framework of chemistry as the ability of an atom to form bonds with other atoms.

Let us explain with an example:

There are two atoms with insignificant differences in electronegativity (C and CL, C and H). As a rule, these are atoms whose structure of the electron shell is closest to the structure of the electron shell of noble gases.

When these conditions are fulfilled, there arises the attraction of the nuclei of these atoms to the electron pair common to them. In this case, electron clouds are not simply superimposed on each other, as in the case of ionic bonding. Covalent bond provides a reliable connection of two atoms due to the fact that the electron density is redistributed and the energy of the system changes, which is caused by the "drawing in" of the internuclear space of one atom of the electron cloud of the other. The more extensive the mutual overlapping of electronic clouds, the linkage is considered to be more solid.

Hence, the covalent bond is the formation that arose through the mutual socialization of two electrons belonging to two atoms.

As a rule, substances with a molecular crystal lattice are formed by means of a covalent bond. Characteristic for the molecular structure are melting and boiling at low temperatures, poor solubility in water and low electrical conductivity. From this we can conclude that the structure of such elements as germanium, silicon, chlorine, hydrogen is a covalent bond.

Properties that are specific to this type of connection:

1. Saturability. This property is usually understood as the maximum number of bonds that they can establish specific atoms. This amount is determined by the total number of those orbitals in the atom that can participate in the formation of chemical bonds. The valence of an atom, on the other hand, can be determined by the number of orbitals already used for this purpose.
2. Directivity . All atoms tend to form the strongest connections. The greatest strength is achieved in the case of coincidence of the spatial orientation of the electron clouds of two atoms, since they overlap each other. In addition, it is this property of covalent bonding as directivity that affects the spatial arrangement of molecules of organic matter, that is , it is responsible for their "geometric shape".
3. Polarizability. This is based on the idea that there are two types of covalent bond:

• Polar or unbalanced. A bond of this type can form only atoms of different species, i.e. Those whose electronegativity is significantly different, or in cases where the common electron pair is asymmetrically divided.
• The nonpolar covalent bond arises between atoms whose electronegativity is practically equal, and the electron density distribution is uniform.

In addition, there are certain quantitative characteristics of the covalent bond:

• The energy of communication . This parameter characterizes the polar connection in terms of its strength. By energy is meant the amount of heat that was necessary to break the bond of two atoms, and also the amount of heat that was released when they were connected.
• By the length of the bond and in molecular chemistry is meant the length of the straight line between the nuclei of two atoms. This parameter also characterizes the strength of the connection.
• The dipole moment is a quantity that characterizes the polarity of the valence bond.