The molecular geometry of a water molecule H2O is determined by its electronic structure, which is based on the arrangement of its valence electrons. In a water molecule, the central oxygen atom has six valence electrons, while each hydrogen atom has one valence electron. When the two hydrogen atoms bond with the oxygen atom, they form two single covalent bonds, leaving four electrons as two lone pairs on the oxygen atom.The electronic geometry of the water molecule is tetrahedral, as there are four electron domains around the central oxygen atom two bonding domains and two lone pairs . However, the molecular geometry, which describes the arrangement of the atoms in the molecule, is bent or angular due to the presence of the lone pairs.The presence of lone pairs affects the bond angle in the water molecule. In a perfect tetrahedral geometry, the bond angle would be 109.5 degrees. However, the lone pairs on the oxygen atom repel the bonding pairs of electrons more strongly than the bonding pairs repel each other. This causes the bonding pairs to be pushed closer together, resulting in a smaller bond angle. The bond angle in a water molecule is approximately 104.5 degrees.In summary, the molecular geometry of a water molecule is bent, and the bond angle is approximately 104.5 degrees. The presence of lone pairs on the central oxygen atom affects the bond angle by causing it to be smaller than the ideal tetrahedral angle.