Question

Which is greater in size fe2 or fe3

Answer 1

The electronic configuration for $Fe(II)$ is $[Ar]3d^6$ and for $Fe(III)$ is $[Ar]3d^5$
As the shell numbers are same in both the elements and number of protons are equal, the size will also be same of both.

Answer 2

both are of same size fe2 and fe3