electrostatic (coulomb) potential energy

[Nicole Ju 3H]

What exactly is electrostatic (coulomb) potential energy? I know it is proportional to (q1)(q2)/r, but I'm confused on what exactly it refers to. Is it related to how stable an atom is?

Thanks!

[Anna Dai-Liu 3B]

I think in the context of what we learned in class, it has to do with the attraction/repulsion between protons and electrons. Between protons and electrons, the overall PE < 0, indicating an attraction, but between electrons where both are negatively charged then the PE > 0, indicating repulsion. This repulsion is what leads to the "shielding" effect between the different electron shells (because the overall charge that outer electrons will experience is smaller due to electron-electron repulsion).