Which of the following atoms has the largest atomic radius? Provide an explanation a Hydrogen
b. Sodium
C Lithium
d Rubidium

d Rubidium

Explanation:

The atomic radius of an atom is the distance from the center of the nucleus to its outermost electron.

The atomic radius of elements varies in the periodic table, it increases as you go down in a group and decreases along the period from left to right.  

All the elements listed: Hydrogen, Sodium, Lithium and Rubidium belong to the same group in the periodic table (group 1), Since atomic radius increases from top to bottom in a group, Rubidium has the largest atomic radius.