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Why does the negative end of a bond dipole lie near the more electronegative atom?

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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.

In a covalent bond, the negative end of a bond dipole lies near the more electronegative atom because of how that atom interacts with the shared electron pair.

Electronegativity is defined as the ability of an atom to attract shared electrons toward itself when part of a compound. Although the bond consists of a shared pair of electrons, the atom with the higher electronegativity exerts a stronger pull on these electrons, drawing them closer to its own nucleus.12

As the shared electrons spend more time in the vicinity of the more electronegative atom, that atom acquires a partial negative charge. Conversely, the atom that has lost its equal share of the electron pair acquires a partial positive charge because its nuclear charge is no longer fully balanced by the shared electrons. This unequal distribution of electrical charge creates an electric dipole, with the negative pole localized on the more electronegative element.2