As you move down a column what happens to the ionic radius?

The ionic radius increases.  

Each time you move down to the next Period, you are adding an extra shell of electrons.

Each shell is further from the nucleus than the one before it, so the .

The image below illustrates the increase in ionic radius as you go down a Group.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.