Must every diatomic molecule always have an equilibrium bond length? That is, is there always a distance between two nuclei such that the Coulomb attraction between the electron and protons counterbalances perfectly the electric repulsion between the protons?

How do we find iron's ionic charge? I was taught that we use roman numerals but I don't see any on the basic periodic table of elements (I'm using this one). So how do we find iron's charge of Fe 2+ or 3+? Again I thought it was the column that told us this but that doesn't seem like the case bec...

When conducting an experiment to identify some common chemicals, I tested crystal/powder samples of the chemicals with moist litmus paper. When I put a piece of blue paper on some $\ce{CaO}$ powder, much to my surprise, it turned an intense, bright purple. When I used a piece of red litmus paper ...