The atomic radii of Cl, I and Br are 99, 133 and 114 pm, respectively.

• Cl, I and Br belong to group 17 (halogen group) in the periodic table.
• As we move down the group from top to bottom in the periodic table, a new shell gets added in the atom of the elements.
• As a result, the effective nuclear charge decreases due to increase in the atomic size as well as increased shielding effect.
• Therefore, the valence electrons experience less attractive force from the nucleus and are held less tightly resulting in the increased atomic radius.
• Thus, their atomic radii increases in the following order down the group. Cl (99 pm) < Br (114 pm) < I (133 pm)

Hence,

The atomic radii of Cl, I and Br are 99, 133 and 114 pm, respectively.