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Why does an electron not fall into the nucleus?

  1. Jun 27, 2015 #1
    Is it because the electron has less mass and is a point object that prevents it from falling into the nucleus due to attraction of protons?
     
  2. jcsd
  3. Jun 27, 2015 #2

    Orodruin

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    At the atomic level the electron is not a classical point object which can be thought of as "falling". It is described by quantum physics and it cannot be in a lower energy state than the ground state.
     
  4. Jun 27, 2015 #3
    I read that

    In quantum physics there is something called "the uncertainty principle" that states that we can't know where something is at the same time as we know where it's going (due to it being a wave). Or rather, the better known somethings position is, the less known is it's movement.

    Now, with this knowledge we can determine what happens if an electron actually "fell" into the nucleus. The position would be well known (it's in the nucleus), but that means it could be moving really fast, so it breaks free from the nucleus again. This means it can't actually fall in.


    Why we can't know where something is at the same time as we know where it's going due to it being a wave. How does being a wave effect this?
     
  5. Jun 27, 2015 #4

    Orodruin

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    You need to stop using the word "fell", even within quotes. What you are describing is only a semiclassical and popular interpretation of quantum physics. The point is that if the electron was localised to the nucleus, it would be in a superposition of states which includes several non-bound states as well as some bound states which are bound but not the ground state. The time evolution of the wave function would quickly result in the electron most likely being somewhere else.

    This is also a popular misconception. Particles in quantum physics are not waves, nor are they tiny balls (i.e., classical particles). They have some properties reminiscent of these objects, but they really are quantum particles. The non-localisability of a quantum particle follows directly from the commutation relation between the position and momentum operators.
     
  6. Jun 27, 2015 #5

    Vanadium 50

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    Before going into the millionth near-identical copy of this thread, may I point out that this is the https://www.physicsforums.com/threads/why-dont-electrons-crash-into-the-nucleus-in-atoms.511179/ [Broken] in the https://www.physicsforums.com/threads/physics-faq-list.807553/ [Broken].
     
    Last edited by a moderator: May 7, 2017
  7. Jun 27, 2015 #6
    I can understand that the electrons orbit the nucleus because there is a centripetal force exerted on the electrons. This centripetal force is due to the attractive force of the protons. But if we observe the Earth which orbits the sun. There is an initial momentum which stops Earth from moving into the sun. Does the electron also have some initial momentum?
     
  8. Jun 27, 2015 #7
    That's another topic. This question is not about a loss of energy doe to emission of EM-radiation but about an electron "falling" into the nucleus of an atom. The answer is, that the probability density of the electron is not zero in the nucleus of an atom and for s-electrons it even reaches its maximum in the center. Thus an electron can "fall" into the nucleus and proton-rich nuclei can capture it.
     
    Last edited by a moderator: May 7, 2017
  9. Jun 27, 2015 #8

    Dale

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    It is possible for an electron to have an orbital with orbital angular momentum, but there are also orbitals without orbital angular momentum, called s orbitals. Since there are some orbitals without angular momentum, angular momentum is not the thing which prevents the electron from being confined to the nucleus.

    In the end, it is just about energy. It would take a lot of energy to confine the electron to the nucleus. So instead it relaxes to a lower energy state where the electron is not confined to the nucleus.
     
  10. Jun 29, 2015 #9

    Drakkith

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    Thread locked, pending possible moderation.
     
  11. Jun 30, 2015 #10

    Dale

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    After discussion the thread will remain locked and several off topic posts have been removed.
     
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