Example Seven : PF5
     
+
Valance electrons on A
5
+
Sigma electrons from B
5
-
Pi electrons from A
0
+
Donated dative electrons
0
+/-
Charge on molecule
0
     
=
Total
10
     
/2
Number of negative centres
5
-s
Number of lone pairs
0
     
Therefore the shape is Trigonal Bipyramidal