effect of lone pair on bond angle
We start with the symmetric possibilities, H2O, OF2, and OCl2. The bond angles and bond lengths of these three molecules are shown below: Note that the bond lengths increase in a way we can understand easily: H is smaller than F, which is smaller than Cl. But look at the bond angles. We have claimed that the two lone pairs on the O atom (not shown) should push the bonding pairs of electrons down, lowering the bond angle from the perfect tetrahedral angle of 109.47Â°.