Model polyelectronic systems

In the article Quantum mechanics of this treatise, we have studied the elementary general principles of quantum physics that will now enable us to understand and analyze atomic and molecular structures, at least the simplest of them. Among these, of course, are the two prototypes, the hydrogen atom and the molecular ion ${\mathrm{H}}_2^{+}$ , for which we know the exact solutions of the Schrödinger equation and which will serve as models for studying more complex structures. In all other cases, exact solutions are not known, and we have to resort to approximation techniques.

What's more, as soon as a system is made up of several identical particles, we have to take into account the indistinguishability between these particles, a purely quantum phenomenon that will give rise to new properties.