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Homework Help: Quantum numbers problem

  1. Nov 28, 2011 #1


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    Gold Member

    1. The problem statement, all variables and given/known data
    List all possible values for the quantum numbers [itex]n[/itex], [itex]l[/itex], [itex]m_l[/itex] and [itex]m_s[/itex] for a state 2p. If an atom has 2 electrons 2p, how many states are there?

    2. Relevant equations
    Simple ones.

    3. The attempt at a solution
    [itex]m_l=-1, 0, 1[/itex].
    [itex]m_s=-1/2, 1/2[/itex].
    Now I'm confused on how to answer the question.
    2 electrons in 2p means 2 electrons with quantum numbers:
    (2,1,-1,1/2) and (2,1,-1,-1/2)
    or (2,1,-1,-1/2) and (2,1,-1,-1/2)
    or (2,1,-1,1/2) and (2,1,0,1/2)
    or (2,1,-1,1/2) and (2,1,0,-1/2)
    or (2,1,0,1/2) and (2,1,-1,1/2)
    or etc.
    I mean an electron can have a certain [itex]m_l[/itex] while the other can have any other [itex]m_l[/itex] incuding the same [itex]m_l[/itex] as the first electron. When they have the same m_l, they must have opposite spin. Is this ok?
  2. jcsd
  3. Nov 29, 2011 #2


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    Homework Helper

    Yes, the only requirement is that the electrons must not have the same quantum numbers. If 3 of them are identical, the 4th is forced to have different values among them.
  4. Nov 29, 2011 #3


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    Gold Member

    Ok thank you. :smile:
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