Page 4 of 6 FirstFirst ... 23456 LastLast
Results 31 to 40 of 57

Thread: Why does the electron orbit the nucleus?

  1. Top | #31
    Elder Contributor
    Join Date
    Feb 2006
    Location
    Here
    Posts
    23,800
    Archived
    16,553
    Total Posts
    40,353
    Rep Power
    81
    Quote Originally Posted by Jimmy Higgins View Post
    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.
    To do organic chemistry you don't even have to talk about mass.

    You abstract an electron to (-1) and call that it's charge and you can predict what it will do and where it will go.

  2. Top | #32
    Contributor
    Join Date
    Sep 2004
    Location
    California
    Posts
    5,076
    Archived
    4,797
    Total Posts
    9,873
    Rep Power
    69
    Quote Originally Posted by barbos View Post
    That makes them less than useless.
    If you say so. Forty-odd years ago I attended a lecture by Dr. Chandrasekhar. He opened with a demonstration of the power of dimensional analysis, using a classical model of the atom to derive a formula in a couple of minutes with which he calculated that the total number of chemical elements was about a hundred. Uselessness appears to be a matter of opinion.

    It's just in QM it stops falling down when it reaches lowest possible orbit, which has zero angular momentum,
    Only in the s orbitals. Most of the electrons in most of the elements still have orbital angular momentum.

    ...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.
    That's the speed in an orbit at the scale of an atom; we were talking what the speed would be if an electron were able to spiral down to the nucleus, about a hundred thousand times closer.

  3. Top | #33
    Fair dinkum thinkum bilby's Avatar
    Join Date
    Mar 2007
    Location
    The Sunshine State: The one with Crocs, not Gators
    Posts
    24,713
    Archived
    10,477
    Total Posts
    35,190
    Rep Power
    97
    Quote Originally Posted by Jimmy Higgins View Post
    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?
    Because electrons are the things being discussed? I wasn't 'calling them out', I was just using them as examples. The photon I picked because it's a convenient zero rest-mass entity with strong relevance to electron behaviour, and exemplifies the fact that I am not just discussing massive particles.
    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.
    Sure.
    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.
    I rather like analogies, and I think they can be very helpful. But not in this case, because there really isn't a commonly experienced entity that is analogous to the things being discussed.
    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.
    It really seems to be neither. It lacks features of both that are widely expected to be defining. For example, a particle has a defined location, and a wave occurs in a medium. Electrons (and photons, and other quantum scale objects) don't fit either criterion.

    As soon as you say "an electron is like a billiard ball", students get a mental model of the thing that is going to need to be un-learned (probably with great difficulty) at some future date, if they want to pursue the subject.

  4. Top | #34
    Elder Contributor
    Join Date
    Feb 2001
    Location
    Located 100 miles east of A in America
    Posts
    31,791
    Archived
    42,473
    Total Posts
    74,264
    Rep Power
    100
    Quote Originally Posted by bilby View Post
    Because electrons are the things being discussed? I wasn't 'calling them out', I was just using them as examples. The photon I picked because it's a convenient zero rest-mass entity with strong relevance to electron behaviour, and exemplifies the fact that I am not just discussing massive particles.
    I think it gets lost that electrons aren't remotely special in this behavior. You are correct though that the subject was electrons, not just 'crap that does "odd" stuff in the quantum world'.

    I rather like analogies, and I think they can be very helpful. But not in this case, because there really isn't a commonly experienced entity that is analogous to the things being discussed.
    The problem is, people are crap with analogies.
    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.
    It really seems to be neither.
    This applies to larger things as well. If buckyballs act as a wave and we "know" that they are particles, it suggests particles themselves aren't exactly just particles.

    As soon as you say "an electron is like a billiard ball", students get a mental model of the thing that is going to need to be un-learned (probably with great difficulty) at some future date, if they want to pursue the subject.
    My question is, if we do a double slit experiment with billiard balls, what is the result? I mean other than using up impossible resources to scale the experiment.

  5. Top | #35
    Elder Contributor DBT's Avatar
    Join Date
    May 2003
    Location
    ɹǝpunuʍop puɐן
    Posts
    11,711
    Archived
    17,906
    Total Posts
    29,617
    Rep Power
    80
    What about this interpretation?

    Quote:
    ''Just to clarify one point, if a single photon is fired at the two slits, an interference pattern will not appear. Rather, a single 'blip' will appear on the screen, which indicates that the photon is not a wave, but rather a particle. If a large number of photons are fired at the slits,an interference pattern will begin to appear. So it seems that photons are really particles that behave collectively like waves. The same reasoning applies to all particles, not just photons.''

  6. Top | #36
    Veteran Member
    Join Date
    Jun 2002
    Location
    West Coast
    Posts
    2,739
    Archived
    7,585
    Total Posts
    10,324
    Rep Power
    73
    Quote Originally Posted by Jimmy Higgins View Post
    My question is, if we do a double slit experiment with billiard balls, what is the result? I mean other than using up impossible resources to scale the experiment.
    When you get to near an Avogadro’s number of particles the coherence length will be impossibly small. Now, if you can make a Bose Einstein condensate large enough it might get interesting.

  7. Top | #37
    Veteran Member
    Join Date
    Jun 2002
    Location
    West Coast
    Posts
    2,739
    Archived
    7,585
    Total Posts
    10,324
    Rep Power
    73
    Quote Originally Posted by DBT View Post
    What about this interpretation?

    Quote:
    ''Just to clarify one point, if a single photon is fired at the two slits, an interference pattern will not appear. Rather, a single 'blip' will appear on the screen, which indicates that the photon is not a wave, but rather a particle. If a large number of photons are fired at the slits,an interference pattern will begin to appear. So it seems that photons are really particles that behave collectively like waves. The same reasoning applies to all particles, not just photons.''
    I don’t like the use of the word “collectively” here. It’s not that an electron interferes with other electrons. It’s more that its wave-like properties interact with the two slits to generate the probability pattern of where the particles will be detected.

  8. Top | #38
    Elder Contributor DBT's Avatar
    Join Date
    May 2003
    Location
    ɹǝpunuʍop puɐן
    Posts
    11,711
    Archived
    17,906
    Total Posts
    29,617
    Rep Power
    80
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by DBT View Post
    What about this interpretation?

    Quote:
    ''Just to clarify one point, if a single photon is fired at the two slits, an interference pattern will not appear. Rather, a single 'blip' will appear on the screen, which indicates that the photon is not a wave, but rather a particle. If a large number of photons are fired at the slits,an interference pattern will begin to appear. So it seems that photons are really particles that behave collectively like waves. The same reasoning applies to all particles, not just photons.''
    I don’t like the use of the word “collectively” here. It’s not that an electron interferes with other electrons. It’s more that its wave-like properties interact with the two slits to generate the probability pattern of where the particles will be detected.
    Yet the author is saying that firing single photons does not produce an interference pattern?

  9. Top | #39
    Squadron Leader
    Join Date
    Dec 2017
    Location
    Land of Smiles
    Posts
    1,495
    Rep Power
    16
    Quote Originally Posted by DBT View Post
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by DBT View Post
    What about this interpretation?

    Quote:
    ''Just to clarify one point, if a single photon is fired at the two slits, an interference pattern will not appear. Rather, a single 'blip' will appear on the screen, which indicates that the photon is not a wave, but rather a particle. If a large number of photons are fired at the slits,an interference pattern will begin to appear. So it seems that photons are really particles that behave collectively like waves. The same reasoning applies to all particles, not just photons.''
    I don’t like the use of the word “collectively” here. It’s not that an electron interferes with other electrons. It’s more that its wave-like properties interact with the two slits to generate the probability pattern of where the particles will be detected.
    Yet the author is saying that firing single photons does not produce an interference pattern?
    A single photon generates a single blip.
    BUT that blip need not be located at point A (where it would fall if it passed through slit #1 specifically) nor at point B (for slit #2). Instead the blip may fall on one of the crests of the interference pattern defined by the two-slit probability wave.


    HELP! I'm a fan of Huw Price's theory that quantum entanglement is the obvious outcome once time's arrow is properly understood. Bell's Theorem and the EPR and GHZ paradoxes cease to be paradoxical. Controversy about hidden variables or locality disappears. However I do not see how to use this insight to understand the 2-slit experiments. (And Huw Price didn't answer my e-mail!)

  10. Top | #40
    Veteran Member Treedbear's Avatar
    Join Date
    May 2016
    Location
    out on a limb
    Posts
    2,567
    Rep Power
    22
    Quote Originally Posted by DBT View Post
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by DBT View Post
    What about this interpretation?

    Quote:
    ''Just to clarify one point, if a single photon is fired at the two slits, an interference pattern will not appear. Rather, a single 'blip' will appear on the screen, which indicates that the photon is not a wave, but rather a particle. If a large number of photons are fired at the slits,an interference pattern will begin to appear. So it seems that photons are really particles that behave collectively like waves. The same reasoning applies to all particles, not just photons.''
    I don’t like the use of the word “collectively” here. It’s not that an electron interferes with other electrons. It’s more that its wave-like properties interact with the two slits to generate the probability pattern of where the particles will be detected.
    Yet the author is saying that firing single photons does not produce an interference pattern?
    A single photon cannot produce a pattern of any kind, let alone behave collectively. It's like any sort of data. A single data point doesn't form a pattern. You need lots of data points to reveal a pattern that might reflect a property of the source of the data.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •