Explanation:
Group 2A elements are Beryllium, Magnesium, Calcium, Strontium, Barium and Radium.
An atom which is largest in size will have the largest ionic radius. Also, it is known that as we move down a group size of atoms increases.
So, in group 2A Beryllium is smallest in size whereas Radium is the largest in size.
Thus, we can conclude that group 2A element which has the largest ionic radius is radium.
