In the second period of the periodic table, there are elements from lithium (Li) to neon (Ne). Among these elements, the one with the largest atomic radius is lithium (Li).
As you move across a period from left to right, the atomic radius generally decreases. This trend is primarily due to the increasing nuclear charge, which attracts the electrons more strongly, resulting in a smaller atomic radius. However, in the case of the second period, lithium (Li) has the largest atomic radius compared to the other elements in that period (beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne)).
Thus, lithium (Li) has the largest atomic radius among the elements in the second period.