Why does Mg2+ have the ionic radii bigger than Ca2+ If they were atoms, $\ce{Mg}$ should have a smaller radii. How does this change?
Source: http://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/Atomic_%26_ionic_radii.svg/551px-Atomic_%26_ionic_radii.svg.png

Ca2+ is bigger than Mg2+