Hello, 1. I read here and here that in the hydrogen atom, electrons move at approximately ~1/137c. In the first link they speak of "zipping around the nucleus", presumably figuratively, because it is often stressed that QM has superseded the earlier model of electrons flying around. Instead we are to think of a probability distribution of both location and velocity - right? But is one to think of the electron as being that probability distribution? If yes, then what does that ~1/137c apply to? It seems like the distribution itself should not be thought of as moving - at least not in an atom unaffected by exterior influences. If no - if the electron is something to which the distribution applies, but is not the distribution itself - then how is it not true that it "zips around" in the classical sense? 2. Here someone writes (emphasis added) "The ground state has momentum zero, so the electron doesn't move at all in any classical sense. Excited states have a non-zero angular momentum, but you shouldn't think of this as a point like object spinning around the atom." How does that relate to the nonzero ~1/137c velocity mentioned? I was assuming that the latter velocity refers to an isolated atom, with non-excited electrons. But here it is said that momentum, and hence velocity (for the electron does have mass), is zero. Or does that refer to the (nill) momentum of the probability distribution? Thanks in advance.