According to the principles of quantum mechanics and molecular structure, the water molecule H2O has a bent or V-shaped geometry. This is due to the presence of two lone pairs of electrons on the oxygen atom, which repel the bonding pairs of electrons between the oxygen and hydrogen atoms.The bond angle in a water molecule is approximately 104.5 degrees. This value deviates from the ideal tetrahedral angle of 109.5 degrees because the lone pairs of electrons on the oxygen atom occupy more space than the bonding pairs, causing the bonding pairs to be pushed closer together. This results in the observed bond angle of 104.5 degrees.