covalent types, the former based on the electric attraction of the negatively charged atom for a positively charged atom, the latter on the sharing of electrons by different atoms; one must think of these two distinct chemical structures as existing simultaneously, in a state called “resonance.”...
and it's huge, so it makes a handy return path for electrons. "Ground" in the power-distribution grid is literally the ground that's all around you when you are walking outside. It is the dirt, rocks, groundwater and so on.
Who discovered electrons? Who published the first atomic theory? Who provided evidence for the existence of an atomic nucleus? Who provided the first evidence that atoms contain subatomic particles? Which scientist developed the quantum mechanical model of the atom? Who first proposed an atomic theory...