explanation of why the atomic radii of the noble gases are the smallest in any given period
In general, the atomic radius of elements decreases as you go across a Period from left to right. As we go across a Period from left to right, electrons are being added to the same energy level, the valence shell.s you go down a Group in the Periodic Table from top to bottom, the number of energy levels or electron shells increases so the atomic radius of the elements increases.