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I'm confused about this excited electron configuration

  1. Feb 23, 2013 #1
    I have already turned in my homework for chemistry however I'm still confused about this question:
    Which electron configuration is in an excited state?
    a.1s2 2s2 2px2
    b.1s2 2s1 2px1 2py1 2pz1

    My teacher told me that the only choice b was excited because choice a was in violation of Hund's rule. I am confused because I thought both of these choices were in violation of Hund's rule, and I'm not sure what the difference is. I know that choice a has an iccorect filling order because for 2px to have 2 electrons both 2py and 2pz would need 1 e-. Also I know that choice b has an incorrect filling order because the 2s needs to be filled before p can have any e-. So I thought both a and b would excited bacause they had electrons in the wrong places. Any and all help with this will be greatly appreciated.
     
    Last edited: Feb 23, 2013
  2. jcsd
  3. Mar 12, 2013 #2
    I understand where you are coming from.

    I think that , although both configurations are in violation of Hund's rule, only b represents a truly "excited" state because an electron from a 2s2 orbital was promoted to 2pz1.

    Choice a, in contrast, is just written improperly. Whereas it should be 1s2 2s2 2px1 2py1, but an electron was demoted to the 2px2.

    This is just my observation, but yes this is a tricky question. Maybe I overlooked something. If you ever find a definite answers, please message me. I'd like to know what it is.
     
  4. Mar 12, 2013 #3

    DrDu

    User Avatar
    Science Advisor

    You are perfectly right.
    Clearly, a is an excited configuration, too.
     
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