Which of the following ions has the largest radius? Br- S2- B3+ Mg2+ Li+

Br - has the largest radius

Explanation:

These ions each have achieved the nearest noble gas configuration. Br - has a like electron configuration to that of Krypton, S2- has a like electron configuration to that of Argon,  B3+ to Helium, Mg2+ to Neon, and Li+ to Helium.

Traveling down a group, the radius tends to increase as atom gains another shell. Here we are comparing elements of like electron configuration to the noble gases Helium, Neon, Argon, Krypton. Krypton, being the last element present in the group out of the 4, has the greatest radius as it has the most shells. Thus, Br - has the largest radius.

Hope that helps!