What do single bond, double bond …

SINGLE BOND

When two atoms share one electron pair between each other, then they are said to be bonded by single covalent bond, denoted by single dash joining the atoms. For the formation of this bond, presence of an atom with single valency is required. The atoms with single valencies are halogens and hydrogen.

e.g. – Cl₂, HCl, NH₃ etc.

DOUBLE BOND

When two atoms share two electron pair between each other, they are said to be bonded by double covalent bond, denoted by double dash joining the atoms. The atoms with double valency are chalcogens or the oxygen family.
E.g.:- O₂, CO₂ etc.

TRIPLE BOND

When two atoms share three electron pair between each other, they are said to be bonded by triple covalent bond. Triple bond is denoted by three dash joining the atoms. The atoms with triple valency are pnictogen or the nitrogen family.

E.g.: N₂ ,  C₂H₂­ etc.