Slap in the face OR Slap on the face?

Hi,
People do say  "Slap on the face", so I wouldn't say it is not good to use "Slap on the face", though I would always use "Slap in the face".

Example:

1) He slapped me in the face. (Correct)
2) He slapped me on the face. (Incorrect)

Cheers!
Naeem