How does the atomic radius of argon compare to that of chlorine?

The atomic radius of an element is a measure of the size of its atoms. Generally, the atomic radius decreases as you move across a period (from left to right) in the periodic table due to increasing nuclear charge pulling the electrons closer to the nucleus. However, within a group (vertical column), the atomic radius tends to increase as you move down the group because of additional electron shells.

Argon (Ar) is in the 3rd period (row) and the 18th group (column) of the periodic table, while chlorine (Cl) is in the 3rd period and the 17th group.

Since argon is located to the right of chlorine in the periodic table (in the same period), its atomic radius is smaller than that of chlorine. This is because argon has more protons in its nucleus, resulting in a stronger attraction to its electrons and thus a smaller atomic radius compared to chlorine.