Final answer:
Electronegativity determines whether a bond is polar or nonpolar covalent. It measures an atom's tendency to attract electrons towards itself. The greater the difference in electronegativity between two atoms, the more polar the bond.
Step-by-step explanation:
Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity. Electronegativity is a measure of the tendency of an atom to attract electrons towards itself. The more an atom attracts the electrons in its bonds, the larger its electronegativity. In a polar covalent bond, the electrons are shifted toward the more electronegative atom, resulting in a partial negative charge on that atom. The greater the difference in electronegativity, the more polarized the electron distribution and the larger the partial charges of the atoms.