Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why does a4n electron need to move in an orbit?

  1. Sep 26, 2010 #1
    Note: This isn't a HW question.

    I have learned that the magnitude of charge of a proton and electron is the same (i.e. 1.602 * 10^19 Columbs). Then why does an electron need to move in an orbit because the charges could cancel each other out and the electron could remain stationary.

    I realize this might be a newbie question but I was just curious.

  2. jcsd
  3. Sep 26, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    It's not a matter of charge "canceling". It's a matter of the existence of an attractive potential. This is similar to the Earth-moon system. Why does the moon needs to orbit the earth? After all, the charges of the Earth-Moon system is already neutral?

    Furthermore, the word "orbit" is rather misleading. You might want to read our FAQ in the General Physics forum to realize that this is not your regular classical orbits.

    I have no idea what a "4n electron" is in your title. I doubt that you're referring only to the 4n energy state, since that is way too specific.

  4. Sep 27, 2010 #3
    The "a4n" electron is simply a typing mistake. I meant it to be "an electron". Also, sorry about the usage of orbits. I am just used to using the word. I read the General Physics FAQ but I have a few questions.

    But I do not still understand why do electrons need to move in the first place? Why can't a stable atom exist with proton and electron both being stationary? What force sets an electron into the moving state in the first place?
  5. Sep 27, 2010 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    You mean you cannot reason out why the moon would not stay where it is with respect to the earth if it isn't orbiting the earth? You do know what a 'central force' is, don't you?

  6. Sep 27, 2010 #5
    Re: Why does an electron need to move in an orbit?

    No I do not know what a central force is. Kindly explain it for me.
  7. Sep 27, 2010 #6


    User Avatar

    Staff: Mentor

    A "central force" is a force whose direction is always towards or away from some central location.

    The gravitational force exerted on an object by the earth is always directed towards the center of the earth (which we assume to be stationary when the object has much less mass than the earth)

    The electrical force that a proton exerts on an electron is always directed towards the proton (which we usually assume to be stationary because the electron's mass is much less than the proton's mass).
  8. Sep 27, 2010 #7
    If a proton and an electron are near each other, they can't be stationary, because they attract (+ and - remember?), but since they are each so small, the chances they actually collide is minute. Chances are the electron will miss the proton and settle in an orbital, depending on its initial speed relative to the proton.

    I'm not sure if an e- and a proton can actually collide (what about opposing accelerated beams?). Maybe a particle physicist can answer this. If so then an electron would have a cross-section and thus a volume. But I don't think that is the case.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook