how does the total energy of a system of atoms decrease as attractive forces predominate repulsive forces? and what leads to the increase in potential energy?
Answers
Answer:
The larger number of attracting interactions simply adds to the difficulty of seeing why the net interaction would be repulsive at short distances.
As for the question of particle distances... Here is an example of why it appears that there are always configurations in which distances between attracting particles are shorter than those between repelling particles:
Place the particles on a circle with an inscribed square such that the protons are at opposite corners of the square and the electrons similarly. Independent of the size of the circle, the attracting pairs are always closer than the repelling pairs. This would appear to apply whether the electrons are visualized as particles or probability distributions ("clouds"). I've tried to attach a rough sketch of this as a pdf or a jpg but despite the size of the files being quite small the system rejects them. I've attached the pdf to a separate email.
The strong attraction of each shared electron to both nuclei stabilizes the system, and the potential energy decreases as the bond distance decreases. If the atoms continue to approach each other, the positive charges in the two nuclei begin to repel each other, and the potential energy increases.