What is the electron configuration of copper?

Copper is in the ninth column of the transition metals in the d block of the fourth energy level of . This would make the for copper, ##1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^9## or in noble gas configuration [Ar] ##4s^2 3d^9##.

However, because the 3d orbital is so much larger then the 4s orbital and the 3d orbital only needs one more electron to be filled, the 3d orbital pulls an electron from the 4s orbital to fill this empty space.

This makes the actual electron configuration for copper [Ar] ##4s^1 3d^10##.