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Homework Help: Deriving the electron speed from a specified orbital

  1. Sep 28, 2014 #1
    [Mentor's note: this thread was moved from a non-homework forum, therefore it does not use the normal template for homework questions]

    What is the speed of the electron in terms of the speed of the light when it is in the n = 3 state in the Hydrogen atom?

    I started with this equation to find the energy En=-E0(z^2/n^2)
    From that i used the momentum=E/c and found momentum then derived v from p=mv
    The system keeps saying im wrong, is there anything specific im missing or maybe an equation i should be using instead?
    Last edited by a moderator: Sep 28, 2014
  2. jcsd
  3. Sep 28, 2014 #2


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    Homework Helper

    Read http://en.wikipedia.org/wiki/Energy–momentum_relation

    Is E=pc true for an electron?

    The total energy of the electron in the Hydogen atom is negative. What do you think, why?

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