Predict whether the atomic radii of the first element will be higher or lower than the second element and...

4. Predict whether the atomic radii of the first element will be higher or lower than the second element and indicate the reason from the list. Use all that apply if there is more than one correct answer.
I less principle energy levels
II more principle energy levels
III stronger nuclear charge due to more protons
IV weaker nuclear charge due to less protons
Read these like this: Pb is __________ than Sn because __________.
Sb In
Mg Be
Ne He