Question

answer the questions in the table below about the shape of the phosphorus trifluoride (pf₃) molecule.
how many electron groups are around the central phosphorus atom?
note: one \electron group\ means one lone pair, one single bond, one double bond, or one triple bond.
what phrase best describes the arrangement of these electron groups around the central phosphorus atom? (you may need to use the scrollbar to see all the choices.)

Explanation:

Step1: Determine bonding and lone - pairs

Phosphorus has 5 valence electrons. In $PF_3$, it forms 3 single bonds with fluorine atoms and has 1 lone - pair. So the total number of electron groups is the sum of bonding pairs and lone - pairs.
$3$ (bonding pairs) $+ 1$ (lone - pair)$=4$

Step2: Identify electron - group arrangement

According to VSEPR (Valence - Shell Electron - Pair Repulsion) theory, when there are 4 electron groups around a central atom, the electron - group arrangement is tetrahedral.

Answer:

How many electron groups are around the central phosphorus atom? 4
What phrase best describes the arrangement of these electron groups around the central phosphorus atom? Tetrahedral