How does atomic radius change with electron configurations?

Atomic radius generally decreases across a period and increases down a group due to electron configurations.

The atomic radius is determined by the electron configuration of an atom. As you move across a period from left to right on the periodic table, the atomic radius generally decreases. This is because as you move across a period, each atom has one more proton and one more electron than the previous one. The additional proton increases the positive charge of the nucleus, which pulls the electrons in the electron cloud closer to the nucleus, thus decreasing the atomic radius.

However, as you move down a group on the periodic table, the atomic radius generally increases. This is because each atom in a group has one more energy level than the previous one. Each additional energy level is further from the nucleus, which increases the atomic radius. The effect of the additional energy level outweighs the effect of the additional proton, so the atomic radius increases.

The electron configuration also affects the atomic radius through the shielding effect. The shielding effect is the reduction in effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the protons in the nucleus and the repelling forces from other electrons in the atom. Electrons in inner energy levels shield electrons in outer energy levels from the positive charge of the protons in the nucleus. As a result, the outermost electrons are not pulled as strongly towards the nucleus, which increases the atomic radius.

In summary, the atomic radius is influenced by the electron configuration of an atom. The number of protons, the number of energy levels, and the shielding effect all play a role in determining the atomic radius. As you move across a period, the atomic radius generally decreases due to an increase in protons. As you move down a group, the atomic radius generally increases due to an increase in energy levels. The shielding effect also contributes to the increase in atomic radius down a group.