chem repulsion(斥力)問題

I always encourage students to "visualise" molecules when studying Chem.

1. bond pair = electron pair in covalent bond
e.g. in H-O-H, there are bond pair electrons in [O-H]
(the "-" represents two electrons in the covalent bond between [O] and [H]

2. lone pair = electron pair NOT in bonding
i.e. in H-O-H, there are two lone pairs in [O]

3. talking about the repulsions
imagine [O] is a sphere and electrons are moving in orbitals around it.
all the lone pairs and bond pairs are in n=2 shell,
but bond pair electrons are "shared" with [H]
making them farther from [O] nucleus.

As the electrons are more remote, repulsion is smaller.
(surface area of a bigger sphere is larger than a smaller sphere
while charges of electrons remain the same).

Therefore, repulsion is the weakest between bond pair- bond pair,
but strongest between lone pair - lone pair,
and that between lone pair - bond pair is intermediate, in general.