Which one has the larger radius strontium atom or an iodine atom?

Strontium has a larger atomic radius than iodine. This is because strontium is located in Group 2 of the Periodic Table and is a metal, while iodine is a nonmetal found in Group 17. As you move down the periodic table, the atomic radius increases due to the addition of electron shells, and strontium, being lower in the table, has more electron shells than iodine.