Atomic Radius

Periods

Row (left-right).

Groups

Column (up-down).

Atomics Radius

Distance between center of the nucleus-outer boundary of an atoms cloud.

Atomic radius decreases:

left-right, down-up

Atomic Radius increases

right-left, up-down

Atoms Are big because

The number of energy levels present. The more electrons there are, they repel each other and dilute the power of the nucleus, so that the electrons aren’t attracted to it.

Atoms are small because

The more protons there are in the nucleus, the nuclear pull is stronger, pulling the outer electrons in and making the atom small.

Atomic radius increases from right-left/up-down because…

There are more energy levels being added therefore more electrons.

Atomic radius decreases from left-right/down-up because…

Electrons are added to the same energy level, and electrons become ineffective at shielding each other, drawing the outer cloud closer to the nucleus.