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Why does water have an angular shape?

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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 water molecule has an angular shape because it is not linear; the two hydrogen atoms are bound to the central oxygen atom at an angle of 104.5°.1

This geometry is often explained using VSEPR theory, which considers the electrostatic repulsions between electron pairs. In a water molecule, the oxygen atom possesses unshared electron pairs that, along with the bonding pairs, influence the molecular structure. Because the molecule is angular rather than linear, the bond dipole moments do not cancel out, resulting in a polar molecule with a nonzero dipole moment.213

While VSEPR theory is a useful rule of thumb for predicting this bent shape, it has limitations, such as not predicting the exact magnitude of the bond angle or accounting for all energy contributions within the molecule. The resulting angular structure is fundamental to water's unique properties, including its ability to act as a solvent and its behavior as a liquid at room temperature.23