What makes the atomic radius change along a period on the periodic table?

As you move from left to right along a period in the Periodic Table, the atomic radius decreases. This is primarily due to the increasing positive charge of the nucleus, as more protons are added, which leads to a stronger attraction between the nucleus and the electrons. Although electrons are also being added, they enter the same energy level without significantly increasing electron shielding, resulting in a net decrease in atomic size. Consequently, the greater effective nuclear charge pulls the electron cloud closer to the nucleus, reducing the atomic radius.