Kid's Rooms Analogy

An analogy for talking about Hund’s rule (where the p orbitals fill up) is that it’s like parents deciding where siblings will sleep. If you have enough rooms you put each person in one room because that's peaceful for everybody and everybody prefers that. If you have an extra child you have a choice of renovating your house, which is expensive and takes a lot of energy, or you put them in the same bedroom. You are going to put them in the same bedroom because you're not going to renovate your house. They get that. Whenever you’re doing that you can go back to, 'Now, are we going to renovate the house? No, we're going to put them in the same bedroom.' To preserve the analogy each bedroom’s only big enough for two kids.