The atom that will have a larger radius than zinc is strontium, Sr.
Atomic radius is defined as the half of the inter-nuclear distance between two covalently bonded atoms of non-metallic elements or half of the distance between two nuclei in the solid state of metals.
Across the period atomic radii decreases progressively due to the increase in nuclear charge.
Down a group atomic radii increase progressively due to the successive shells of electrons being added.
Since strontium satisfies the criteria, it has the larger atomic radius.
