Question

the atom with the largest atomic radius in group 18 is -

Explanation:

Step1: Recall atomic - radius trend

Atomic radius increases down a group in the periodic table due to the addition of electron - shells.

Step2: Identify positions of elements

Ar (argon), Rn (radon), Kr (krypton), and He (helium) are all in Group 18. Rn is the lowest in the group among them with the most electron - shells.

Answer:

Rn