So I am looking through my book and it says ".... the order of the excited states is exactly the same order (3p-4s-3d-4p)".
But now I am looking at a question in the book and it says "Is 3d to 4s transition possible? Why or why not?"
My answer to this question is: No it can't be because it doesn't abide by the selection rule because the difference in the orbital quantum numbers is 2 instead of 1.
Now if this is the case, why does the above statement have the oder of (3p-4s-3d-4p) if we know there cannot be a transition between the 4s and 3d state like this order says?