[sunnysd]

Does anyone know how to determine the size of an ion? Is it based on which sublevel they're at or how full the orbitals are? Like would an ion thats in the 3p level with only 1 electron be bigger or smaller than an ion in the 2p level with 5 electrons? If that even makes sense...

[enahs]

Does anyone know how to determine the size of an ion?

Quantum Mechanics; advanced mojo. Serious math. There are methods for quick estimations, or relative sizes.

Like would an ion thats in the 3p level with only 1 electron be bigger or smaller than an ion in the 2p level with 5 electrons? If that even makes sense...

Which one has more electrons? Generally, that one will be bigger. There are factors, however such as effective nuclear charge; which can complicate things (http://en.wikipedia.org/wiki/Effective_nuclear_charge).

[sunnysd]

We went over quantum mechanics... was that mole and stuff or no that was about waves right? How would that work? It's probably the electron shells.

[Borek]

From crystallographic data - they give information about distances between nuclei.