As one moves across the 4th period from left to right, the valence electrons go into the same shell, and the atomic radius decreases. The decrease in atomic radius is due to the increase in the attraction of the nucleus for the electrons in the shells.

Question

Quizplus · Accepted Answer

As you move across the 4th period from left to right, the number of protons (and thus the nuclear charge) increases while the valence electrons are added to the same energy level. This increased nuclear charge pulls the electrons closer, decreasing the atomic radius.

As One Moves Across the 4th Period from Left to Right