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How do electrons orbit the nucleus?

  1. Dec 23, 2014 #1
    I have heard that instead of orbiting the nucleus they actually pop into and out of existence around the nucleus forming the electron cloud, and where they relocate depends on the probability of that area due to wave function, am i right?
     
  2. jcsd
  3. Dec 23, 2014 #2

    Nugatory

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    You are right that they don't actually orbit the nucleus (and therefore that the Rutherford atom that's the default avatar here isn't a correct picture :) ).

    However, popping into and out of existence is also a misconception - it's widely promulgated in the pop-sci press, but that doesn't make it right.

    There are a bunch of threads here on this subject, but probably the best way of describing it is to say that the electron has no position (and that is literally "no" position, not "it's somewhere but we don't know exactly where") unless and until it interacts with something else in a way that locates it (an "observation" in the lingo). The mathematics of quantum mechanics give the probability that we will find the electron at various locations if we measure it, but says nothing about where it is when otherwise.
     
  4. Dec 23, 2014 #3
    So what your saying is that atom is really just the nucleus and that's pretty much it. You can say that it's surrounded by the electron cloud (which is a spread out wave), however this wave is not real, it's completely imaginary and is just used for a mathematical tool. Unless you are saying that electron cloud is made by the electron constantly popping in and out of existence around the atom (making the electron cloud a physical thing), then the atom is really just made up of the nucleus.
     
  5. Dec 23, 2014 #4
    Remember the nucleus is a lot more energy than its quarks and gluons, the strong nuclear force dominates close.
     
  6. Dec 23, 2014 #5

    Nugatory

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    No, not even that. The protons and neutrons that make up the nucleus are also quantum particles so also have no definite position if not measured. All that's going on is that the wave function for the particles in the nucleus has a much narrower and higher central peak, so the probability of finding them in a very small area at the center of the atom is very high.

    If you google for "Schrodinger equation hydrogen atom" you will find the standard solution for Schrodinger's equation for a single electron around a hydrogen nucleus consisting of one proton and zero, one, or two neutrons. The derivation of this solution assumes that the nucleus is a single point precisely fixed at the center of the atom but this assumption is actually just a (very good) approximation.
     
  7. Dec 23, 2014 #6
    But before you said that a particle will have a position if they interact with something else. Quarks do this all the time inside the proton/neutron. Quarks interact with the other quarks in the proton or neutron with gluons. So therefore, the nucleus will always have a definite position because quarks are always interacting with each other.
     
  8. Dec 23, 2014 #7
    Also, let me add is that it is this constant interaction between the quarks of a proton/ of a neutron that give us about 99.99% of our mass.
     
  9. Dec 23, 2014 #8

    Nugatory

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    I said "interacts with something else in a way that locates it". These interactions don't do that, as the quarks and gluons are also quantum particles with no definite position. All that we have is a high probability that if measure the position of any of these particles there is a high probability that we will find it within the same small volume of space. But we cannot perform such a measurement without somehow interacting with something outside the nucleus.
     
  10. Dec 24, 2014 #9
    If quarks literally have no location in the proton/neutron, then how can they physically exchange particles and color?
     
  11. Dec 24, 2014 #10
    And what would a particle interact with that would give the particle a real location?
     
  12. Dec 24, 2014 #11

    Nugatory

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    There's no particular reason why they must have a specific position to engage in these interactions, and I'm not sure why you would think that they should.

    Are you perhaps thinking that these particles are like very small objects moving thorugh the space inside the nucleus, that they exchange color by moving close enough to one another that the color charge jumps from one to the other the way that a static electricity spark jumps from my finger to a doorknob, that when they exchange gluons the way that two warships exchange gunfire, shooting gluons across the space between them? If so, you would not be the first person to be misled by the words "particle" and "exchange"; in the context of quantum mechanics those words mean something very different than their meaning in generally spoken English. "Particle" is perhaps the most unfortunate of all, as it leaves people thinking that we're talking about some sort of tiny object, like an infinitesimal grain of sand except even smaller.

    You really have to learn quantum mechanics first, before you can move on to quantum field theory where the real nature of the particles is revealed.
     
  13. Dec 24, 2014 #12

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    A basic example: A particle strikes a piece of photographic film. When it does, a spot appears on the film and we can say that that's where the particle was at the moment that the spot appeared. However, until that interaction happened the wave function had non-zero amplitude across a much wider region of the film, and there was no meaningful way that we could say it was "here" instead of "there".

    For particles confined within a nucleus or electrons around the nucleus, we obviously cannot insert a tiny piece of photographic film in there and the interactions that we can make happen are not especially helpful in localizing the particles.
     
  14. Dec 24, 2014 #13

    bhobba

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    What you are talking about is virtual particles in Quantum Field theory. This exchange thing is just pictorial vividness for certain mathematical terms that appear in the equations and is not meant to be taken literally.

    To really understand it you need to study the theory, which I invite you to do after a bit of familiarity with QM:
    https://www.amazon.com/Quantum-Mechanics-The-Theoretical-Minimum/dp/0465036678 (to gain a smattering of QM)
    https://www.amazon.com/Quantum-Field-Theory-Gifted-Amateur/dp/019969933X (takes off from about where the above ends)

    This is literature for the serious student - it will require effort - but will take you much further than popularisations.

    Thanks
    Bill
     
    Last edited by a moderator: May 7, 2017
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