What characteristic differentiates polar covalent bonds from nonpolar ones?

Polar covalent bonds are distinguished by the unequal sharing of electrons between two atoms. In a polar covalent bond, one atom has a greater electronegativity than the other, meaning it has a stronger attraction for the shared electrons. This causes the electron density to be skewed more towards the more electronegative atom, resulting in a dipole moment where one end of the bond has a slight negative charge and the other end has a slight positive charge.

This characteristic is crucial in understanding molecular polarity, which has implications for physical properties such as solubility and boiling points. By contrast, in nonpolar covalent bonds, the electrons are shared equally between the two atoms, resulting in no significant charge separation and therefore no dipole moment. The other options refer to concepts that do not accurately describe the nature of bond polarity and are irrelevant in the context of distinguishing between polar and nonpolar covalent bonds.