Covalent Bond
A chemical bond formed between two atoms by mutual sharing of the electron between them so as to complete their octels or duplets is known as the covalent bond and the number of electrons contributed by each atom is known as covalency. E.g., the formation of CI2.
In covalent bonding, the shared pairs of electrons present between the atoms are called bond pairs while unshared pairs or nonbonding electron pairs are known as lone pairs.
Single Covalent Bond
A covalent bond formed by the mutual sharing of one pair of electrons is called a single covalent bond, or simply a single bond. A single covalent bond is represented by a small line (-) between the two atoms.
Double Covalent Bond
A covalent bond formed by the mutual sharing of two pair of electrons is called a double covalent bond, or simply a double bond. A double covalent bond is represented by two small horizontal line (=) between the two atoms. E.g., O=O, O=C=O etc.
Triple Covalent Bond
A covalent bond formed by the mutual sharing of three pairs of electron is called a triple covalent bond, or simply a triple bond. A triple covalent bond is represented by three small horizontal lines (≡) between the two atoms. E.g., N≡N, H-C≡C-H etc.
Formation of a Covalent Bond
Formation of a covalent bond is favoured by
- High ionization enthalpy of the combining elements.
- Nearly equal electron gain enthalpy and equal electro-negativities of combining elements.
- High nuclear charge and small atomic size of the combining elements.
Polar Covalent Bond
The bond between two unlike atoms which differ in their affinities for electrons is said to be polar covalent bond. E.g. H-Cl