Asked by tom

whats the noble has configuration for chromium?
is it [Ar] 4s^2 3d^4
Answered by bobpursley
Nope, nope, nope.

[Ar] 3d5 4s1
you need some practice on looking at energy levels, and memorizing them.
Answered by tom
how is it 4s1?
Answered by bobpursley
There are two exeptions to the filling order: Copper and Cr.

https://www.brightstorm.com/science/chemistry/the-atom/exceptions-to-electron-configuration/