# Based on the VSEPR theory, what is the molecular geometry of a molecule of PI3?

##### 1 Answer
Dec 28, 2014

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 geomerty and a trigonal planar molecular geometry.

Here's a representation of $P {I}_{3}$'s molecular geometry: