Explanation:
First, we will construct the Lewis dot structure of
PBr3. Phosphorus will contribute 5 electrons while each bromine atom will contribute 7 which means we need to have 26 electrons in PBr3. The skeleton of PBr3 must contain 3 Br atoms with two shared electrons with the P central atom. But this will only correspond to 6 electrons. The 20 electrons must be given to each of the Br atoms as lone pairs and one lone pair in the P atom.
Since there are four electron groups around P, its electron geometry is tetrahedral. As for the molecular geometry, it is expected to be trigonal pyramidal since one of the four electron groups is a lone pair. The structure below shows PBr3
when the shared electrons arde represented as single bonds.
