What distinguishes polar covalent bonds from nonpolar covalent bonds?

Polar covalent bonds are characterized by the unequal sharing of electrons between two atoms. This unequal sharing occurs due to a difference in electronegativity between the bonded atoms. Electronegativity is the tendency of an atom to attract electrons in a bond. In a polar covalent bond, one atom has a stronger attraction for the electrons than the other, leading to a situation where the shared electrons are drawn closer to the more electronegative atom. As a result, this creates a dipole moment, where one end of the molecule has a partial negative charge and the other end has a partial positive charge.

This differential distribution of electron density is what distinguishes polar covalent bonds from nonpolar covalent bonds, where the electrons are shared equally because the atoms involved have similar electronegativities. In nonpolar bonds, there is no charge separation and, consequently, no dipole moment is produced.

In summary, the essence of polar covalent bonding lies in the unequal sharing of electrons, leading to the formation of dipoles and distinct charge distributions within the molecule.