For example, if you have two hydrogen atoms and an oxygen atom, they are all electrically neutral and don't attract each other. But then if they manage to get "close enough" somehow they snap together releasing energy, and to get them apart again requires energy be input into the system.
This says that the bound state is a 'lower energy' state than the unbound state, and this is my question:
From a Quantum Mechanical point of view, where does this energy come from that is released when the bond is formed?
I've done some reading and it has something to do with filling electron shells and electron probability wavefunctions spreading between atoms, and something about the Virial Theorom where the kinetic energy of the electron is reduced as it's range of area is increased.
But that doesn't make sense to me, so I was wondering if someone could explain where the bond energy released comes from in terms of the electron wavefunctions? Assume high school physics/freshman maths.