It turns out that it's actually an infinitesimally small fraction of the volume of the atom where-- the volume of the atom is hard to define, because the electron can pretty much be anywhere, but if you view the volume as where you're most likely to find the electron, or with 90% probability you're likely to find the electron, then the nucleus is, in a lot of cases and the way I think about it, it's about 1/10,000 of the volume.