What is the electron configuration of copper? Why is it NOT #[Ar]3d^9 4s^2#?
And this "anomaly" arises from not recognizing the difference in energy between the
Hence, it should be clear that the
That gives rise to the so-called "anomalous configuration", which is in fact the correct, normal one when one properly follows the Aufbau principle (lowest energy fills first!):
#barul(|stackrel(" ")(" "[Ar] 3d^10 4s^1" ")|)#
The reason why one would get
But that wouldn't make sense, since the
(It is just a poor interpretation of the Aufbau principle by inference off of pre-transition metals, and follows from habitually using the periodic table