Electronic configuration of copper \(=2,8,18,1\)
When copper loses one electron then it becomes a positive ion that is \(Cu^+\).
No of electrons in ionic \(Cu^+\,=\) atomic no. of copper \(-\) no. of electrons lost
\(=29-1=28\)
Therefore electronic configuration of copper ion \(Cu^+\, 2,8,18.\)
This means that \(Cu^+\) has \(18\) electrons in its outermost shell.