Taking hydrogen chloride and methane as examples, distinguish between a polar covalent bond and a non-polar covalent bond.
In a polar covalent compound, covalent bond is formed between two different atoms with different electronegativities. For example, hydrogen chloride is a polar covalent compound in which hydrogen and chlorine have different electronegativity values. This electronegativity difference causes the shared pair of electrons to move towards chlorine atom. As a result, chlorine atom attains partial negative charge and hydrogen atom attains an equivalent positive charge.
In a non-polar covalent compound, covalent bond is formed between two atoms with similar electronegativity. For example, in methane, carbon atom and hydrogen have similar electronegativity values; therefore, the shared pair of electrons lies in between these two atoms. As a result, no charge is developed on either atom.