Final answer:
The nonmetal element with the largest ionic radius is iodine (I) because it is located below bromine (Br) in Group 7 (the halogens).
Step-by-step explanation:
The ionic radius of an element is determined by the number of electrons and the effective nuclear charge. In general, as you move down a group in the periodic table, the ionic radius increases due to the addition of new energy levels. Among nonmetal elements, the one with the largest ionic radius would be the one that is located at the bottom of a group. For example, iodine (I) would have the largest ionic radius among nonmetals because it is located below bromine (Br) in Group 7 (the halogens).