Which has the largest radius k plus na plus na k?

The ionic radii of ions can vary based on their charge and coordination number. In the case of K⁺, Na⁺, and the combination of NaK, K⁺ typically has a larger radius than Na⁺ because potassium is located lower in the Periodic Table and has more electron shells. Therefore, K⁺ has the largest radius among K⁺ and Na⁺. If you meant "NaK" as a compound, it does not have a defined ionic radius like individual ions do.