# Periodic Table and Atomic Radius

Well Wikipedia says that the atomic radius is lowered for elements in a group closer to noble gases (same row). It also says that those elements want to keep their valence electrons more than metals, for example. But the atomic shielding of those elements is bigger than the metals one because there are more electrons to repel. How is that possible?

You've now increased the nuclear charge by a full unit of charge, but the increase in shielding is not commensurate. That means that the effective nuclear charge ($$Z_{\mathrm{eff}}$$) has increased, pulling all of the valence electrons closer to the nucleus.