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Questions About Subatomic Particles

  1. Mar 3, 2007 #1
    Hi, new here. Love Physics.

    I have a few question if you all don't mind my asking...

    1) Can a proton, neutron, or electron be said to have a velocity? I'd say yes, but just want to make sure before I go on.

    2) Let us suppose that in the universe, there are only two particles. One electron, and one proton. Would these two particles attract one another regardless of velocity? For example, if both had "0 velocity", would they still attract one another?

    3) Most subatomic physics that I've learned so far seems centered around the protons/electrons. How exactly does a neutron play a role in the atom when the supposedly are neutral, and therefore do not become engaged in the pulls from protons/electrons?

    I realize that I may be way off on some of the things I'm suggesting in my questions, and please forgive me. I'm, as you should say, a physics newb.

    Thankies. :)
  2. jcsd
  3. Mar 3, 2007 #2


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    1) All velocities are relative.
    2) Electromagnetic force would make proton and elctron approach each other - forming a hydrogen atom.
    3) Strong force keeps protons and neutrons together inside atomic nuclei.
  4. Mar 3, 2007 #3

    Another one I forgot to ask earlier,

    Electrons circle the "nucleus" of an atom, which contains the protons/neutrons. In the case of a hydrogen atom, why does the electron begin to "orbit" the proton instead of continuing to approach it?
  5. Mar 4, 2007 #4


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    from a classical electro-mechanical POV, if they where both point charges then any approach, other than exactly dead on, will result in missing and an elliptical orbit.

    but quantum mechanics say that electrons to "orbit" (in an orderly and traditional manner) the nucleus but rather that their appearance at any particular place and time is a random number that would be what you would get evaluating the expectation value of the resulting solution of Schrodinger's equation. it doesn't move in a Newtonian manner. isn't that why they needed to make QM?
  6. Mar 4, 2007 #5
    Physical quantities like protons, electrons etc etc obey the rules of QM, of which the uncertainty principle is a basic ingredient. This principle states that you can determin exactly the position of a particle (the accuracy is limited by the device's accuracy) but if you measure several particle's (ie repeat the same measurement) you will get a spread in the position values.

    Velocity requires that you have info on how the trajectory of a particle changes with respect to time. Since we will have a spread on the trajectory (ie position) we will also have this spread in velocity values. Hence, velocity (which is a CLASSICAL concept by definition) has no real physical values for the atomic scaled phenomena.

    In short, the answer is NO !

    Ofcourse, but if the distance is infinitely large, the attraction is 0

    You are asking for quite a lot here and i do not know how deep we can go into this but i suggest you read this

  7. Mar 4, 2007 #6

    Claude Bile

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    Atomic nucleii exist in an equilibrium between the attractive strong nuclear force and the repulsive electromagnetic force. Neutrons add to the attractive strong nuclear force, thus helping overcome the electromagnetic repulsion and thus stabilising the atom. Think of neutrons as being the nuclear "glue" that holds everything together.

  8. Mar 4, 2007 #7


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    Staff: Mentor

  9. Mar 9, 2007 #8

    Thanks for the answers everyone.
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