4. Vindobonium
It would be great to study the pseudo-atomic element vindobonium. Suppose energy is equal to the mininum distance that two 'electrons' must be away from each other such that the electrons will be emitted when they obtain enough energy/minimum distance from each other would mathematically require an electron to be required to leave in order for the constraint to be obtained.
There are many kinds of distances, aka metrics.
We can even do something like half-life by having 'protons' or 'neutrons' that act like billiards that are capable of leaving like radioactive half-lives