If two elements are from the
same period, which element is most
likely to have the largest atomic
radius, the element from Group 13
or the element from Group 17?

The element from Group 13.

Explanation:

Following trends of the periodic table, atomic radius of the elements increase going down from the right side and decrease on its way up diagonally to the left. (sry if u can't understand me)

neutrons are in the middle of the atom and the electrons, which are much smaller.

that tool would be a compass