whats the noble has configuration for chromium?

Question

is it [Ar] 4s^2 3d^4

Answer 1

Nope, nope, nope.

[Ar] 3d5 4s1
you need some practice on looking at energy levels, and memorizing them.

Answer 2

how is it 4s1?

Answer 3

There are two exeptions to the filling order: Copper and Cr.

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