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How does a polar covalent bond differ from a nonpolar covalent bond?

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Diagram showing the formation of a polar covalent bond in a water molecule, with two hydrogen atoms bonding to one oxygen atom to form H2O, illustrating shared electrons and chemical reaction. — covalent bond In polar covalent bonds, such as that between hydrogen and oxygen atoms, the electrons are not transferred from one atom to the other as they are in an ionic bond. Instead, some outer electrons merely spend more time in the vicinity of the other atom. The effect of this orbital distortion is to induce regional net charges that hold the atoms together, such as in water molecules.

The primary difference between a polar and a nonpolar covalent bond lies in the distribution of electrical charge between the bonded atoms, which is determined by their relative electronegativity.12

Nonpolar Covalent Bonds: These occur when electrons are shared equally between two atoms. This typically happens when the atoms are identical (homonuclear), such as in $H_{2}$ or $C l_{2}$ , resulting in an electrically uniform bond with a dipole moment of zero.12
Polar Covalent Bonds: These form between atoms of different elements with unequal electronegativities. The more electronegative atom attracts the shared electron pair more strongly, acquiring a partial negative charge, while the other atom acquires a partial positive charge. This separation of charge creates an electric dipole, making the bond polar.12

Bonding is best understood as a continuum; as the electronegativity difference between atoms increases, the bond shifts from nonpolar to polar, and eventually to an ionic bond when one atom gains effective control over the shared electrons.12