wat is the oxidation # of F in PF5?????

Answer 1

-1.

You are puzzled that PF5 does not make an octet for P. This is one of the many breakdowns of the Lewis theory, two-electron bond, octet rule. The miracle is that in most other places, it holds up well. In particular, when you go on to study organic chemistry, you will find that it is a sturdy edifice.

Oh, by the way, if F is -1, then the oxidation number of P is +5. But then, that is the valence of phosphorus in PCl5 also. (LOL)