In general, the atomic radius of an atom as you move down a column in the periodic table? increases decreases increases then decreases remains constant

increases

Explanation:

The elements in the periodic table are arranged in order of increasing atomic numbers. The horizontal rows are called as periods and vertical columns are called as groups.  

The elements in the groups are arranged in order of increasing atomic numbers and thus the electrons are being added.The electrons are added to new energy shells.

But the effect of addition of new shells outweighs the increase of nuclear charge and thus the atomic radius of the atoms will keep on increasing as we move down a column in the periodic table.