Question

Based on the VSEPR theory, what is the molecular geometry of a molecule of $P{I}_3$?

Answer 1

VSEPR Theory allows for the prediction of molecular shapes based on the number of electron pairs that surround their respective atoms.

In order to determine the molecular shape of the $P{I}_3$ molecule using VSEPR Theory, its Lewis structure must first be determined.

SInce P has $5$ valence electrons, and each I atom has $7$ valence electrons, the molecule's Lewis structure will look like this:

Notice that P uses $3$ valence electrons to form covalent bonds with the three I atoms, which leaves it with one lone pair of electrons.

P has a steric number of $4$ and a coordination number of $3$, which means that it has a tetrahedral electron geometry and a trigonal planar molecular geometry.

Here's a representation of $P{I}_3$'s molecular geometry: