Water molecules have a bent or V-shaped geometry due to the presence of two lone pairs of electrons on the oxygen atom and the nature of the oxygen-hydrogen bonds.
In a water molecule (H2O), oxygen is more electronegative than hydrogen, meaning it has a stronger attraction for electrons. As a result, the oxygen atom pulls the shared electron pairs in the covalent bonds closer to itself, creating a partial negative charge (δ-) on the oxygen atom and partial positive charges (δ+) on the hydrogen atoms.
Additionally, the oxygen atom has two lone pairs of electrons that are not involved in bonding. These lone pairs also exert electron-electron repulsion, which influences the molecular shape.
To minimize electron-electron repulsion, the hydrogen atoms in water molecules tend to be as far apart as possible. This results in a bent shape, with the oxygen atom at the center and the two hydrogen atoms at an angle of approximately 104.5 degrees relative to each other.
The bent shape of water molecules allows for optimal distribution of electron density, minimizing repulsion between electron pairs. It also gives water its unique properties such as polarity, hydrogen bonding, and the ability to form a variety of intermolecular interactions.