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Thread: Why does the electron orbit the nucleus?

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    The lowest electron state in an atom has zero orbital angular momentum. So, the probability distribution function actually peaks at the position of the nucleus. If I recall correctly this results in a slight shift in the energy level.

    There’s just no good classical analogy for what’s happening to quantum particles.

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    We can use equations to model the behavior of a ripple in an electron field.

    We can model behavior.

    This allows us to predict behavior at a certain scale.

    There is a little question about Muon g-2 behavior.

    Why does an electron have it's properties and thus it's behavior?

    What gave it these properties?

    That is a bigger question.

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    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by James Brown View Post
    Why don't the electrons and the protons click together like all all things with opposite charges do?
    The electron can only exist in quantized energy states within the potential well generated by the. nucleus. No zero energy state is allowed.

    In classical EM, an orbiting electron would emit radiation and it would spiral into the nucleus. That was one clue that modern physics needed to be invented to explain the structure of the atom.
    But it does happen! In neutron stars. If gravity is strong enough, the electron and the proton get smashed together. Of course they then turn into a neutron.

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    Mazzie Daius fromderinside's Avatar
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    Think fields.

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    Contributor skepticalbip's Avatar
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    Quote Originally Posted by fromderinside View Post
    Think fields.
    Are you suggesting that fields are a real physical entity rather than just a mathematical model that allows for the prediction of behavior?

    The gravitation field is quite useful but uncle Albert says it is only a convenient math model.

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    Quote Originally Posted by SLD View Post
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by James Brown View Post
    Why don't the electrons and the protons click together like all all things with opposite charges do?
    The electron can only exist in quantized energy states within the potential well generated by the. nucleus. No zero energy state is allowed.

    In classical EM, an orbiting electron would emit radiation and it would spiral into the nucleus. That was one clue that modern physics needed to be invented to explain the structure of the atom.
    But it does happen! In neutron stars. If gravity is strong enough, the electron and the proton get smashed together. Of course they then turn into a neutron.
    Sure, but the question was about atoms, not neutron stars.

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    Quote Originally Posted by barbos View Post
    There is no intuitive picture. And THAT's the point.
    I.e., classical approximations are wrong. Does that make them useless? It seems to me that's in the eye of the beholder. One could ask the same question about planets: why don't they fall onto the sun the same way everything that goes up comes down? One could give the same answer: they have angular momentum so the planet would have to speed up to a ridiculous extent. One could raise the same objection to the answer: the angular momentum is carried away as gravity waves. It seems to me that doesn't make the Newtonian picture of celestial mechanics useless; YMMV.

    Suppose light weren't quantized and the "ultraviolet catastrophe" were real -- how fast would an electron be going when it hit the nucleus?
    Does not matter, classical EM radiation still carry angular momentum.
    Sure; but how much angular momentum would leak away in the emitted light and how much would remain in the electron, hence, how fast would the electron be going? Back of the envelope, I make it about three times the speed of light...

    Also, ultraviolet catastrophe is a separate problem.
    Oh, okay, my bad. Can you explain the distinction?

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    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by SLD View Post
    But it does happen! In neutron stars. If gravity is strong enough, the electron and the proton get smashed together. Of course they then turn into a neutron.
    Sure, but the question was about atoms, not neutron stars.
    And in quantum mechanics, everything is more complicated than any simple summary. Once in a while, if the various energy levels are just right, the electrons and the protons in atoms really do click together like all things with opposite charges do. Radioactive rubidium-83 decays by electron capture. An electron and a proton turn into a neutron and emit a neutrino to carry away the extra angular momentum, just as if it were in a neutron star.

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    Elder Contributor barbos's Avatar
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    Quote Originally Posted by Bomb#20 View Post
    I.e., classical approximations are wrong. Does that make them useless?
    That makes them less than useless.
    It seems to me that's in the eye of the beholder. One could ask the same question about planets: why don't they fall onto the sun the same way everything that goes up comes down? One could give the same answer: they have angular momentum so the planet would have to speed up to a ridiculous extent. One could raise the same objection to the answer: the angular momentum is carried away as gravity waves. It seems to me that doesn't make the Newtonian picture of celestial mechanics useless; YMMV.
    Your theory is not even wrong. Electron rotating around nucleus DOES lose angular momentum and DOES fall, in both in QM and in classical mechanics. It's just in QM it stops falling down when it reaches lowest possible orbit, which has zero angular momentum,
    Does not matter, classical EM radiation still carry angular momentum.
    Sure; but how much angular momentum would leak away in the emitted light and how much would remain in the electron, hence, how fast would the electron be going? Back of the envelope, I make it about three times the speed of light...
    1/137 of speed C.
    Also, ultraviolet catastrophe is a separate problem.
    Oh, okay, my bad. Can you explain the distinction?
    One is about black body radiation, another about electron falling on a nucleus due to radiation.

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    Quote Originally Posted by bilby View Post
    Electrons and photons really aren't like anything in human experience at the macroscopic scale.
    Curious, why call out photons and electrons? The effects we see in atoms can be similar as well. The double slit experiment can be done with buckyballs which are enormously massive compared to electrons.

    I do wonder whether it might be better to start by saying that it's futile to attempt any analogy, and just give students the facts, and show them the experimental approaches that allowed us to determine what those facts are.
    Honestly, analogies are overleveraged for value. I hate analogies because they rarely ever describe what needs to be described.

    What is an electron? It is mass bearing and negatively charged.
    Is it a wave or a particle? It really seems to be whatever it needs to be at the moment.

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