So I was reviewing chemistry lesson and I am curious when I saw the electron configuration in the VIB group:
For $\ce{_24Cr}$ we write the electron configuration $\ce{_18[Ar] 4s^1 5d^5}$ instead of $\ce{_18[Ar] 4s^2 5d^4}$,
For $\ce{_42Mo}$ we write $\ce{_36[Kr] 5s^1 4d^5}$ instead of $\ce{_36[Kr] 5s^2 4d^4}$,
But why for Tungsten $\ce{_74W}$ we do write $\ce{_54[Xe] 6s^2 4f^14 5d^4}$ and not $\ce{_54[Xe] 6s^1 4f^14 5d^5}$?
Is it because after the $\ce{f}$ subshell the rule is not valid anymore?