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Exceptions to the Aufbau Principle

  1. Dec 3, 2012 #1
    Are chromium and copper the only exceptions to the Aufbau Principle? If not, what are all the exceptions? Is there a list of some sort that would state all the exceptions to the Aufbau

    Thank you.
  2. jcsd
  3. Dec 3, 2012 #2
    Upon quick examination of the periodic table, yes they seem to be the only exceptions But keep in mind this is an experimental fact and pretty much all the elements have been tested for the validity of principle for each of them, so if there were any other exceptions, they would probably been known by now! SO for now you can bank on these two exceptions without worrying about the rest, because at this point in time there dont seem to be any other ones!
  4. Dec 4, 2012 #3


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    The answer to that question depends to a large degree on the definition of the aufbau principle, i.e. on the method by which you determine the energies of the underlying atomic orbitals.
  5. Dec 16, 2012 #4
    Try these:

    How Good is the Quantum Mechanical Explanation of the Periodic Table?, Journal of Chemical Education, 75, 1384-1385, (1998)
    Why the 4s Orbital Is Occupied before the 3d, Journal of Chemical Education, 73, 6, 498-503, (1996) (Co-authored with M. Melrose).

    There's also an interesting article from JCE that I can't seem to find that's all about how to empirically motivate orbitals from ionization potentials. That'll also be of interest to you.
  6. Dec 16, 2012 #5


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    They (Cr and Cu) draws one electron from 4s orbital to get half filled/fully filled 3d orbital, granting them pseudo-inert configuration, thus stabilizing them. This phenomena is shown by other members of their respective groups like (Cr, Mo) and (Cu, Ag, Au).
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