Depending on the number of electron pairs shared, covalent bond is single [-], double [=], or triple [≡] covalent.
Hydrogen — Each of the ‘H’ atoms contribute one electron so as to have one shared pair of electrons between them. Both atoms attain stable duplet structure resulting in the formation of a single covalent bond [H-H] between them.
Chlorine — Each of the two Cl atoms contributes one electron so as to have one shared pair of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a single covalent bond [Cl–Cl] between them.
Oxygen — Each of the two O atoms contributes two electron so as to have two shared pair of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a double covalent bond [O=O] between them.
Nitrogen — Each of the two N atoms contributes three electron so as to have three shared pair of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a triple covalent bond [N≡N] between them.
