Question

What is the molecular shape for both `NF_3` and `XeCl_4`?

Answer 1

Simple VSEPR theory predicts a trigonal pyramid for `NF_3`, and square planar for `XeCl_4`.

Explanation:

The electron pairs, bonding and non-bonding, are arranged around nitrogen in the shape of a tetrahedron. Because we describe molecular geometry on the basis of actual atoms, the geometry of the `NF_3` molecule is trigonal pyramidal.

On the other hand, around the xenon atom there are 4 bonding pairs, i.e. 4 `Xe-Cl` bonds, and 2 lone pairs on Xe. These are arranged in the shape of a octahedron, with the non-bonding electron pairs trans with respect to each other. Because we describe molecular geometry on the basis of actual atoms, the geometry of the `XeCl_4` molecule is square planar.