CHEMISTRY COMMUNITY

How do lone pairs affect the bond angles for each shape? Does the bond angle increase or decrease due to lone pairs?

Increased repulsion between the lone pair and bonding pairs results in a slightly smaller bond angle.
See the examples I did in class (ammonia, water, etc.).

The presence of lone pairs will cause all the bond angles in the atom to be slightly smaller than their original size, however we are not responsible for knowing how much the repulsion will affect this. We only need to know that the lone pairs make the bonds smaller.

I find that by knowing the strengths of repulsions (Lone pair & lone pair > Lone pair & bonding pair > bonding pair & bonding pair) is helpful to understand that there will be more repulsion if there are lone pairs therefore causing the angles to become smaller around.