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A really basic question.

  1. Dec 24, 2008 #1
    This is a really basic question but, why are the electrons revolving around the nucleus, why not just stick to the protons in the nucleus?

    And since, the electrons repel, it would explain the reason for the space between the atoms right? Anyway an atom is electrically neutral, so that also fits into it.

    Besides, the nucleus contains neutrons that split up into an electron and proton pair when hit by a high energy particle.

    And the reason for the repulsion of the alpha particles in the scattering experiment could just be that it hits the dense core which is neutral and comes back, like hitting a wall, it does not actually have to be positive to repel right?

    I suppose, what I am asking is, couldn't the nucleus just be a bunch of electrons and protons clumped together? Why add revolving electrons in the mix? As far as I understand it, there is no direct proof of revolving electrons, we can't actually see it.

    This would get rid of the strong and weak forces and make the whole thing a lot simpler.

    I am probably making grave errors in my thinking, but I don't know, it just does not make sense to me.

    Please don't go berserk on me... o:)
  2. jcsd
  3. Dec 24, 2008 #2


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    Please start by reading an entry in our FAQ in the General Physics forum.

  4. Dec 24, 2008 #3
    Okay, thanks, I did. That cleared up a lot of things.

    But, I am assuming smeared means you plot the probability of the particle in an area where it is most probable to occur.

    So, is the electron around the nucleus or is it attached to it?

    And if it hovers above the nucleus, what forces it to stay there?

    And if it is attached to the nucleus, then does it not violate HUP?

    Merry Christmas to you.
  5. Dec 24, 2008 #4
    If the moon hovers above the Earth, what forces it to stay there?

  6. Dec 24, 2008 #5
    I doubt that its the same thing. The moon hovers above the Earth only because the Earth is in constant motion. Its sort of like a dance that they do, the earth pulling on the moon, the moon pulling on the earth and they both in turn being pulled by the sun.

    But, that's not the case with the atoms. The nucleus ain't going anywhere, at least not unless the whole object itself is moving. Besides, that and this have a lot of other differences.
  7. Dec 24, 2008 #6
    What you're saying is absurd. The Moon "hovers" above the Earth only because the Moon is in constant motion relative to the Earth - orbiting around the Earth. The Earth attracts the Moon gravitationally, and the Moon is performing a roughly circular motion around the Earth because of this attraction. The overall motion of the Earth/Moon is irrelevant, because you can always pick an inertial reference frame where the centre of mass of the Earth and Moon is stationary.

    Likewise, in an atom, the electrons are in constant motion. As a classical approximation, the electrons are orbiting around the nucleus, just as the Moon orbits the Earth; the only difference is that the attraction is electric instead of gravitational. This classical approximation isn't precise - the electrons don't do neat orbits - but it should give a fairly good idea of what's going on.

    According to quantum mechanics, it is true, however, that there is some (small) chance of actually finding an electron inside the nucleus. The Wikipedia article on the hydrogen atom explains the quantum mechanics a little further.
  8. Dec 25, 2008 #7
    Hmmm, well that just puts more questions in my head.

    Is there an explanation of what set about this orbiting in the first place. As far as I have read here and there, the reason the planets move in a curved path is because the Huge mass of the sun curves space - time and hence even though they are all actually following straight lines, it looks curved to us.

    But this cannot be the case of the atom right? So, why do the electrons orbit the nucleus then? I just cannot understand the reason behind the orbiting.

    I thank you for your continued patience. :smile:

    Oh... and merry Christmas!! :approve:
  9. Dec 25, 2008 #8


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    Then I don't think you've understood what you've read in the FAQ.

    Here's something to ponder. If an object "orbits" something, that object will have an angular momentum. So far, so good. Yet, an electron in an s-orbital has a .... ZERO angular momentum. None! So how does it "orbit" a nucleus"?

    This implies that the standard, classical notion of "orbits" is not right. It may be a good visual representation of it, and it may be useful in many situations, but one cannot hang on to such a thing to base all our explanations. This is what has been said in the FAQ, that such classical orbits may be meaningless.

    If you drop the concept of an electron particle doing an orbit, and you adopt the QM description of the system via the Schrodinger equation, then the issue of electron orbits no longer arises. A spherically symmetric spread of an electron around the nucleus DOES produce a net angular momentum of zero, and that's the geometry of the s-orbitals.

    However, if you're not willing to drop such classical ideas, then no amount of talking will solve your conceptual problem.

  10. Dec 25, 2008 #9
    Hmmmm... I suppose a deeper understanding of QM is required before I understand. Okay, thank you, I will read on, on my own. Someday, the quantum weirdness is bound to seep in... :biggrin:
  11. Dec 25, 2008 #10


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    I think you've hit on something that could help you here. Yes, if it is attached to the nucleus (in a classical, mechanical sense), then that would violate HUP. So, it is precisely the electron's inability to violate that principal which causes it to "hover above" (or "orbit around") the nucleus. Although it would be more precise to say that this property of the electron is what causes it to be located "within the area defined by" its orbital.

    If not for the HUP (if the electron were a classical particle, like a little "ball"), then the electron probably would just attached itself to the nucleus. Specifically, it would be attached to the protons and nucleus by magnetic attraction. It is a balance between this attraction and the HUP that determines the orbital of the electron around the nucleus.
  12. Dec 25, 2008 #11
    Well said. You should try to get a basic understanding of classical mechanics, quantum theory, and Special/General relativity before you try to come up with your own variations of them. They are all very interesting, I suggest you read Stephen Hawking's book - "A Brief History of Time". That is what initially inspired me to get into physics and maths, It explained the basics very clearly.
  13. Dec 25, 2008 #12


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    Don't be so sure. Steven Weinberg, no less, said that it was one of the most difficult books for him to understand.

  14. Dec 25, 2008 #13
    The last third of the book is quite heavy going, but the majority of it is OK.

    Have you read it?
  15. Dec 25, 2008 #14


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    Yup, and I had the same impression, that it was a very difficult book to understand IF one actually knows the physics behind many of the things he covered. There are many things that are superficially easy. Brian Greene's book is one example. But if you actually know the physics, then it is a daunting task to actually figure out what he is actually doing.

  16. Dec 25, 2008 #15
    Hmmm... Well, I did read the brief history of time. It was interesting, but it didn't seem tough. But I guess as ZZ said, only someone who knows physics would be able to understand why its tough. I have a long way to go.

    Consequently, I got the Feynman series of lecture books and although what he says is pretty new and interesting. I find it tough to go on. I have hardly finished the first book. Any book that is not, let say.... bland and yet deals with physics in detail?
  17. Dec 25, 2008 #16
    I like Lee Smolin's "The Trouble with Physics" and I also like Google (hint, hint)
    Google turns out a hundred of basic intros to all of the physics, and not only on Wikipedia
    Here is a site I like:
    And here is the explanation of the electron-orbit-thing from that site:

    Have fun. In the Feynman's Lectures remember to ignore the equations and it will become the most interesting and insightful book you ever had. The equations will be very useful when you enter college, though.
  18. Dec 26, 2008 #17
    Hmmm... that is a good Idea. Ill try ignoring the equations. I am not going to study physics in coll anyway. I just have an interest.

    Anyway... thanks...:approve:
  19. Dec 26, 2008 #18
    Roger Penrose: The road to reality.

    This book is definatly not dumbed down, it explains everything, and keeps all the mathematics in. Although consequently it is difficult to get a grasp on a lot of the concepts involved. If you wan't a completely thorough description of physics, from beginning to end, then get that one.
  20. Dec 26, 2008 #19
    k... will put it on my list. :smile:
  21. Dec 26, 2008 #20
    When considering a concept like this, you would also have to explain the atomic bomb.
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