How does ionic radius change within a group of metals?
Ionic radius increases as you move from top to bottom on the periodic table.
Ionic radius decreases as you move left to right across the periodic table.
The first one is simple, more shells, more shielding, also there is less effective nuclear charge as the shells are further away from the pull of the nucleus
The left to right, the problem there is that the shell is getting packed with more electrons. the ionic radius decreases for metals forming cations, as the metals lose their outer electrons. The ionic radius increases for nonmetals as the effective nuclear charge decreases due to the number of electrons exceeding the number of protons.