Principal Quantum Numbers are to do with those energy zones that the properties of electrons occupy in atoms.
Consider H2O and HCl. The difference between them more minimal than some alternatives, less complication.
Electrons is the dynamic stuff that makes these things stick together. How much energy does it take to break those two molecules apart? Thinking about these shells and levels and what is different about an electron at one level v another, and why might that be, that is what would you expect, see what you come up with.
Now turn to shape.
Say there are two struggling intents. One is spread evenly, and the other is join forces, with 4 electrons if you had 2 each joining forces on each side of an atom you'd have symmetry and strength - wouldn't you.
Is that wrong? What do you think?