# How do the ionic radii of Fe^(2+) and Fe^(3+) compare?

What do you think? I am hardly sticking my neck out if I predict that the ionic radii of the $\text{ferric ion}$ IS MARKEDLY LESS than that of the $\text{ferrous ion}$. Why?
You know (i) that the atom is mostly empty space; and (ii) that atomic radius can be estimated on the basis of the valence electrons. In the case of $\text{ferric ion}$ you have removed 3 of these valence electrons, and the ionic radius should decrease appropriately. And now this is your job: find estimates for atomic and ionic radius on the web, and see how they compare.