Henry: So after helium comes lithium with three electrons. That third electron must go into a new and different orbital called the 2s orbital.
Me: The 2s orbital is like the 1s orbital except it's bigger, right?
Henry: Not exactly. It's not like those Russian matrushka dolls where the next bigger shell simply encompasses the previous one. The 2s orbital interleaves the 1s orbital so that its electrons can stay closer to the core without getting in the way of the others. Likewise the 3s orbital interleaves the 2s and the 1s. Look at these cross-sections:
Me: Why are you even showing me this stuff? Trooper York says he hates chemistry.
Henry: I'm just trying to explain why the toy metals like lithium, sodium, and potassium are so boring -- not the whole of chemistry.