How do we know that the nucleus is at the center of the atom? I know about the Geiger/Marsden experiment and also of its results. They observed a few α-particles scattering almost at 180°. Hence they concluded that there must exist a high density, positively charged "center" in the atom. But on what basis was it concluded that this "center" must be at the center of the atom? Why not on one side or in random locations for random atoms?