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Ground state energies

  1. Nov 18, 2008 #1
    1. The problem statement, all variables and given/known data

    What are the energies of the ground state and the first two excited states of the He+ ion?



    2. Relevant equations

    En= - Eo/n2



    3. The attempt at a solution

    n=1 for this problem (since there is only 1 electron) so the ground state would have the electron contained in the 1s subshell. Thus E= -13.6eV(1/12)=-13.6eV

    The first excited state has the electron entering the 2s subshell, and the second excited state in the 2p subshell? What I'm getting confused about (assuming my solution for E for the ground state is correct) is that since n=1, the answer won't change depending on what subshell it is in according to how I am approaching the problem. And this I beleive is incorrect.... Any thoughts, help? Thanks!
     
  2. jcsd
  3. Nov 18, 2008 #2

    Dick

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    Ok. Doesn't the energy of the ground state of a one electron atom depend on the charge of the nucleus? -13.6eV is the ground state energy for hydrogen. The general formula depends on Z^2 where Z is the charge of the nucleus. Look it up!
     
  4. Nov 18, 2008 #3
    Ok I see where the text book was getting the -13.6 eV from now, I was looking at the section on the Hydrogen atom since I knew I needed to be dealing with one electron atoms. According to the text book it is -78.98 eV. So then is the energy in the two excited states goin to be this value squared?
     
  5. Nov 18, 2008 #4

    Dick

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    The two excited states are n=2 and n=3 for Z=2 nucleus. There is also a 1/n^2 in the formula you are looking for.
     
  6. Nov 19, 2008 #5
    I understand now how to find the energies of the first two excited states by using the ground state energy. I do not however understand how to get the ground state energy without looking it up. What formula would I use?
     
  7. Nov 19, 2008 #6

    Dick

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    http://en.wikipedia.org/wiki/Hydrogen-like_atom Skip down to the formula for E_n. The ground state is the energy for hydrogen times Z^2.
     
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