As you move down the periodic table from carbon through lead, atomic radii

generally increase. This is because each successive element in a period has one additional electron and one additional proton, which leads to the electrons being drawn more closely to the nucleus and a smaller atomic radius. However, as we move down a group, the number of electron shells increases, which results in a larger atomic radius. Therefore, overall, as we move down the periodic table from carbon through lead, the atomic radii generally increase.