Characteristics of covalent compounds

Characteristics of covalent compounds

1.     Covalent compounds are formed by the mutual sharing of electrons. There is no transfer of electrons from one atom to another and therefore no charges are created on the atom. No ions are formed. These compounds exist as neutral molecules and not as ions. Although some of the covalent molecules exist as solids, they do not conduct electricity in fused or molten or dissolved state.

2.     They possess low melting and boiling points. This is because of the weak intermolecular forces existing between the covalent molecules. Since, no strong coulombic forces are seen, some of covalent molecules are volatile in nature. Mostly covalent compounds possess low melting and boiling points.

3.     Covalent bonds are rigid and directional therefore different shapes of covalent molecules are seen.

4.     Most of the covalent molecules are non polar and are soluble in nonpolar (low dielectric constant) solvents like benzene, ether etc and insoluble in polar solvents like water. Carbon tetrachloride (CCl4) is a covalent nonpolar molecule and is soluble in benzene.

Covalent bond

A covalent bond is a chemical bond formed when two atoms mutually share a pair of electron. By doing so, the atoms attain stable octet electronic configuration. In covalent bonding, overlapping of the atomic orbitals having an electron from each of the two atoms of the bond takes place resulting in equal sharing of the pair of electrons. Also the interatomic bond thus formed due to the overlap of atomic orbitals of electrons is known as a covalent bond. Generally the orbitals of the electrons in the valency shell of the atoms are used for electron sharing. The shared pair of electrons lie in the middle of the covalent bond. Including the shared pair of electrons the atoms of the covalent bond attain the stable octet configuration. Thus in hydrogen molecule (H2) a covalent bond results by the overlap of the two s orbitals each containing an electron from each of the two H atoms of the molecule. Each H atom attains '1s^{2 '} filled K shell.

A covalent bond can be formed by sharing of s,p,d,f electrons also. Consider Cl₂ molecule. The outer shell electronic configuration of atom is 3s² 2p_x² 2p_y² 2p_z¹. When each chlorine atom mutually share the 2p_z unpaired electron contributed from each Cl atom of the molecule, a covalent bond is formed. By doing so, each chlorine atom attains argon electron configuration.