Question

part h
determine the molecular geometry of pf₃.
trigonal planar
bent
trigonal pyramidal
linear
tetrahedral

Explanation:

Step1: Calculate the steric number

The steric number \(SN\) is calculated as \(SN=\text{number of bonding pairs}+\text{number of lone pairs}\).
For \(PF_{3}\), phosphorus (\(P\)) has 5 valence electrons. Each \(F\) atom forms a single bond with \(P\), so there are 3 bonding pairs. The number of lone pairs on \(P\) is \(\frac{5 - 3\times1}{2}=1\). So \(SN = 3 + 1=4\).

Step2: Determine the electron - pair geometry

According to the VSEPR (Valence - Shell Electron - Pair Repulsion) theory, when \(SN = 4\), the electron - pair geometry is tetrahedral.

Step3: Determine the molecular geometry

Since there is 1 lone pair and 3 bonding pairs, the molecular geometry is trigonal pyramidal. The lone pair - bond pair repulsion is stronger than bond pair - bond pair repulsion, which distorts the tetrahedral electron - pair geometry to trigonal pyramidal.

Answer:

trigonal pyramidal