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Homework Help: Electron configuration

  1. Feb 17, 2006 #1
    why is the electron configuration different for Z<20 and Z>90?
  2. jcsd
  3. Feb 17, 2006 #2
    Can you please develop?
  4. Feb 17, 2006 #3
    1s<2s<2p<3s<3p<3d<4s<4p ????
  5. Feb 18, 2006 #4
    Well, at 90 the actinides start. They have different electron configuration, but not in the way you say (4s is always ahead of 3d). When moving on to the actinides, the f subshell is being filled.

    When doing chemical/physical notation of orbitals it is correct to write


    aswell as:


    However, it is important to remember that the (>3)d orbital is filled before the (>4)s orbital.
  6. Feb 18, 2006 #5
    is there a reason why that is so?
  7. Feb 18, 2006 #6
    Do you mean why the actinides are filling their f sunshell or why 4s is filled before 3d?
  8. Feb 18, 2006 #7


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    read up on the Aufbau principle
  9. Feb 19, 2006 #8


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    Out of curiosity :

    1. Where did you read this ?

    2. What does the source say about 20 < z < 90 ?
  10. Feb 23, 2006 #9
    well, i'm taking a class called crystal fracture and that came up in the lecture notes, but didn't explain why...
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