electron configuration exceptions

[Cavalli_1H]

what were the electron configuration exceptions, and does anyone know why they are exceptions? additionally, other than asking what the exceptions are on an exam, what kind of questions would test this knowledge of exceptions?

[Jessica Booth 2F]

what were the electron configuration exceptions, and does anyone know why they are exceptions? additionally, other than asking what the exceptions are on an exam, what kind of questions would test this knowledge of exceptions?
The exceptions that we need to know are Cr whose electron configuration is [Ar]3d^5 4s^1, Cu: [Ar] 3d^10 4s^1, Mo: [Kr] 4d^5 5s^1, and Ag: [Kr]4d^10 5s^1

[Kendall 3H]

Thank you, this was very helpful!

[KTran 1I]

Along with being able to recognize the exceptions and write them, it is probably helpful to understand the reasoning behind the exceptions. The reason why the electron configurations in the post before this one ([Ar]3d^5 4s^1, Cu: [Ar] 3d^10 4s^1, Mo: [Kr] 4d^5 5s^1, and Ag: [Kr]4d^10 5s^1) are written as such is because a half-filled or completely filled d subshell is more stable than a partially filled one. Therefore, usually an electron from the s subshell will get excited and move to the d subshell to make the atom more stable.