Question

What is the molecular shape of `PF_3`?

Answer 1

`"Trigonal pyramidal"`

Explanation:

There are 4 regions of electron density around the central phosphorus atom, one of which is a lone pair. Given simple VSEPR, a structure based on a tetrahedron is specified. But because we describe structure in relation to atoms, and not electron pairs, the structure of `PF_3` should be pyramidal, an analogue of ammonia.

This site reports that `/_F-P-F=107""^@`, so it seems that we are not too offbase. The `/_F-N-F=102.5""^@` in `NF_3` is included for comparison.