V:(Ar) 3d3 4s2
Cr:(Ar) 3d5 4s1 ( in order to gain extra stability 3d4 takes in e- from raw and becomes 3d5 4s1)
Mn:(Ar) 3d5 4s2
Fe:(Ar) 3 d6 4s2
First electron from 4s1 ( 1st I.E.)will go then 3d5 remains
It is half filled, hence symmetrical, so hardest to remove
So2end I.E. odd Cr greatest