Question

What is the vsepr model for PCl3?

Answer 1

`"Trigonal pyramidal"`

Explanation:

We gots `PCl_3`, and around the central phosphorus atom there are `3xx"bonding electron pairs"`, the `P-Cl` bonds, and a `"phosphorus-centred"` lone pair.

To a first approximation, these electron pairs arrange themselves in a tetrahedron........with ideal bond angles of `109.5^@`. But we describe molecular geometry on the basis of the geometry of the ATOMS, not on the electron pairs. The symmetry descends from tetrahedral to trigonal pyramidal with `/_Cl-P-Cl` angles of approx. `100-103^@` due to the disproportionate influence of the phosphorus lone pair.