General Knowledge question

[NPFD]

If an Na atom is positively charged and a Cl atom is negatively charged then what creates the repulsion since they have an equalibrium seperation?

 

[FZ+]

As far as I know, when we are talking charges, we are talking net charges on consideration on the balance of protons and electrons. At large distances, we can generalise this in terms of single "positively charged/negatively charge" particles. But as we get closer, this is no longer true, and other factors come into play, such as proton-proton charge repulsion from the two nuclei.