29 Cu⁺. We have to place 29 electrons and then we will substract 1 electron because of the positive charge.
The electron configuration of Cu should be:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹
2 + 2 + 6 + 2 + 6 + 2 + 9 = 29
Then Copper has one anomalous thing. The energy difference between the 3d and 4s orbitals is very low. It's an exception, but one electron jumps from the subshell 4s to the subshell 3d. In that way it has the subshell 3d that is lower in energy filled, and it is more stable. So the electron configuration of 29 Cu is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
To write the electron configuration of 29 Cu+ we take off one electron from the 4s orbital. S
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰
It has 18 valence electrons (3s² 3p⁶ 3d¹⁰).