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Homework Help: Energy levels

  1. May 7, 2006 #1
    The diagram shows some of the energy levels of an electron in a mercury atom. Level Q represents the lowest possible energy level.

    bilde.png

    (a)Explain why a line spectrum results from an atom with such energy levels.

    (b) Calculate the energy change in joules when the electron moves from level P to level Q and determine the wavelength of the spectral line associated with this transition.

    (c)Explain what is likely to happen if a moving electron of energy 7.0eV collides with an isolated mercury atom in the ground state.

    (d)Explain what is likely to happen if a photon, also of energy 7.0eV were to be incident on the atom.

    Planck’s constant = 6.6 x 10-34 Js,
    speed of light = 3.0 x 108m/s,
    charge on an electron = 1.6 x 10 -19 C

    Thanks in advance
     
  2. jcsd
  3. May 7, 2006 #2
    I have at least tried to solve b)

    -10,4 - (-5,5) = -4,9 eV = -7,84 * 10^-19J


    f = E/h = (- 7.84 * 10^-19)/(6.63 * 10^-34) = - 1.18 * 10^15

    lamba = (3 * 10^8)/(-1.18 * 10^15) = - 2.54 * 10^-7
     
  4. May 7, 2006 #3
    Have I done something wrong?
     
  5. May 7, 2006 #4

    Hootenanny

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    Nope, this looks correct to me.

    ~H
     
  6. May 7, 2006 #5
    Hi

    1) is not that important, I can always find some information on internet on it.

    However, I didn't find any information in my textbook on c) and d). Anyone able (wanting? ...) to help me out?
     
    Last edited: May 7, 2006
  7. May 7, 2006 #6

    Hootenanny

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    Think in terms of 'if the electron / photon collides with an electron from a mercury nucleous'. With electron-electron collisions, the collision can either be elastic or inelastic. With a photon, all the energy is always absorbed by the electron. What happens if an electron gains energy?

    ~H
     
  8. May 7, 2006 #7
    I'm not completely sure
     
  9. May 7, 2006 #8

    Hootenanny

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    Think about energy levels, excitation....

    ~H
     
  10. May 7, 2006 #9
    I believe that the mercury atom would be excitated if it collides with a moving electron.
     
  11. May 7, 2006 #10

    Hootenanny

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    You would need to consider the energy of the electron, in relation to the energy levels of the mercury atom.

    ~H
     
  12. May 7, 2006 #11
    I don't think the mercury atom would be ionized
     
  13. May 7, 2006 #12

    Hootenanny

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    No it wouldn't, what I'm getting at is you should make reference to the energy of the electron / photon in your asnwer and compare it to the energy levels. Excitation is a key word you should use.

    ~H
     
  14. May 7, 2006 #13
    10.4 - 7 = 3.4 eV
     
  15. May 7, 2006 #14

    Hootenanny

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    Correct, so it would be excited to the -3.7eV energy level.

    ~H
     
  16. May 7, 2006 #15
    Thanks

    What would then happen in d?
     
  17. May 7, 2006 #16

    Hootenanny

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    As, I stated previously;

     
  18. May 7, 2006 #17
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