Exceptions to the Aufbau Principle

smaan

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
Principle?

Thank you.

aaku516

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!

DrDu

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.

Einstein Mcfly

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.

AGNuke

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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smaan	Exceptions to the Aufbau Principle Tweet 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 Principle? Thank you.

DrDu Recognitions: Science Advisor	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.

AGNuke	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).