Question

Question #bf3dc

Answer 1

Rb is larger than Na because Rb has more energy levels.

Na atoms are larger than Cl atoms because the electron cloud of Cl is pulled in more tightly by the increased number of protons in the nucleus.

Na+ ions are smaller than Cl- ions because the Na+ ions have electrons in only two energy levels and Cl- ions have electrons in three levels.

Here's a video that will help with any further questions you might have about periodicity.