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Electrons orbiting or not

  1. Dec 29, 2012 #1
    Hi.

    I have a little question. In some of my books you can read that the author keeps saying that an electron is orbiting around the nucleus in it's orbital, and if I'm not mistaken, some equations, or explanations, actually comes from assuming that electrons are orbiting the nucleus in a circular motion.
    I'm just beginning quantum physics, so there is probably alot more advanced stuff that describes those things better, and not assuming that it is orbiting.

    But, as far as I can understand, an electron doesn't orbit the nucleus, like a planet does, but instead, statisticially, is everywhere in the orbital, and actually doesn't "move" but just appear out of "nothing".
    So isn't the assumptions about electrons orbiting a nucleus wrong, and therefor equations that assume this also wrong, or am I misunderstanding something.


    Regards
     
  2. jcsd
  3. Dec 29, 2012 #2
    You're right. So called "old quantum theory" is taught in intro courses and so loads of people who just take those end up believing that that's how QM describes electrons in atoms. Not true.
     
    Last edited by a moderator: Dec 29, 2012
  4. Dec 29, 2012 #3
    Electrons in atom orbitals have nonzero momentum. So if you treat them clasically, you can say that they are moving.

    However, electrons are not tiny balls, they are quantum field excitations. What is moving is not their center of mass, but their probability density current. You can imagine it as a vessel shaped as a circular loop, filled with water. The water is flowing in a vessel (has nonzero momentum), but it doesn't change position.
     
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