According to quantum mechanics, a water molecule H2O has a bent or V-shaped molecular geometry. This is due to the presence of two lone pairs of electrons on the oxygen atom, which repel the two hydrogen atoms, causing the H-O-H bond angle to be approximately 104.5 degrees. The oxygen atom is more electronegative than the hydrogen atoms, which means it attracts the shared electrons in the covalent bonds more strongly. This results in a polar molecule with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms.This polarity leads to strong intermolecular interactions between water molecules, known as hydrogen bonding. A hydrogen bond occurs when the partially positive hydrogen atom of one water molecule is attracted to the partially negative oxygen atom of another water molecule. These hydrogen bonds are responsible for many of water's unique properties, such as its high boiling point, high heat capacity, and high surface tension.In summary, the bent shape and polar nature of water molecules, as described by quantum mechanics, lead to strong hydrogen bonding between water molecules, which in turn affects their intermolecular interactions and gives water its unique properties.