Answer:
Fe2+ is greater in size than Fe3+. Consider the electronic configuration of Fe2+[Ar] 3d6 and Fe3+[Ar] 3d5 (For comparison, Fe [Ar] 4s2 3d6). Fe3+ ionic radius is 63 pm, while Fe2+ has an ionic radius of 77 pm. ... This is because the outermost electron in the Fe2+ ion is pulled off to form Fe3+ ion.
