The electronic configuration of valence shell of Cu is `3d^(10)4s^(1)` and not `3d^(9)4s^(2)`. How is this configuration explained?

The electronic configuration of valence shell of Cu is 3d^(10)4s^(2) . How is this configuration explained ?

The electronic configuration of valence shell of Cr in the ground state as 3d^(5)4s^(1) in stead of 3d^(4)4s^(2) . Give reason.

Electronic configuration of copper is 3d^(10)4s^(1) instead of 3d^(9) 4s^(1) .Why?

(A) : The electronic configuration of Cr is [Ar]3d^(5)4s^(1) but not [Ar]3d^(4)4s^(2) (R) : Lowering energy with configuration [Ar]3d^(5) 4s^(1) is more than that with configuration [Ar]3d^(4)4s^(2)

(A) : The electronic configuration of Cr is [Ar]3d^(5) 4s^(1) but not [Ar]3d^(4) 4s^(2) (R) : Lowering energy with configuration [Ar]3d^(5)4s^(1) is more than that with configuration [A]3d^(4)4s^(2)

The electronic configuration of copper is [Ar] 4s^(1) 3d^(10) and not [Ar] 4s^(2) 3d^(9) . Justify.

Outer electronic configuration of Cu is ul(3d^9) ul (4s^2) .

Electronic configuration of M^(3+) is [Ar]3d^(10)4s^(2) , it belongs to