What defines a polar covalent bond?

A polar covalent bond is characterized by the unequal sharing of electrons between two atoms. This occurs when the atoms involved have different electronegativities, which is a measure of an atom's ability to attract and hold onto electrons. When one atom has a significantly higher electronegativity than the other, it pulls the shared electrons closer, creating a dipole moment where one end of the molecule has a slight negative charge and the other end has a slight positive charge. This unequal distribution of electron density leads to the polarity of the bond.

In contrast, a bond where electrons are shared equally is termed a nonpolar covalent bond. In ionic bonding, electrons are completely transferred rather than shared. Saying that electrons are found only around one atom does not accurately capture the nature of covalent bonding, whether polar or nonpolar; in covalent bonds, electrons are involved in a shared interaction between the participating atoms.