HUND'S RULE OF MAXIMUM MULTIPLICITY

In Chemistry, there is a rule that states that if two or more orbitals of equal energy are available, then electrons will occupy them singly before filling them up in pairs. And if two electrons do pair up, they will do so with opposite spins.

I've started to travel a lot by bus because of University. One day, I came early and the bus was mostly empty; there must have been only two people sitting in two different rows. Then and there, a thought struck me: "We are electrons" because I went and sat in a different row to the two people present altogether. If given the choice, you will always sit in a row of seats that is unoccupied. Obviously, we need to assume that you are boarding the bus by yourself, otherwise, this whole concept fails. This piece has been in the process for a very long time; I simply couldn't figure out how to transfer this discovery onto paper.

The merry-go-round in the drawing has three sets of bus seats; these are the three orbitals (more specifically p-orbitals). To pair up in one of these orbitals, electrons need to have opposite spins; this is being shown by the bus seats facing opposite directions in each pair.

Now, to represent how electrons occupy the orbitals singly, I used colours. When you try to book tickets to the cinema online, you can choose which seats you'd prefer and there's always a colour code system: red=occupied, green=unoccupied, grey=seat you selected (not all cinemas have the same exact colour code, but you get the gist of it). In the merry-go-round, two pairs have one red seat meaning that those two 'orbitals' are occupied by a single electron each. The last 'orbital' has one green and one grey seat; that's where the third electron would sit (that's where I sat on that eventful day).

The reason why I used a merry-go-round is that an atom is universally represented as a nucleus surrounded by electrons in a spherical shape, and the merry-go-round seemed the best shape for this case. The leaves at the bottom are for decorative purposes only; they are multicoloured because I used to have lots of fun on merry-go-rounds. It's a pity there are not many of them around anymore.