We have to determine the number of valence electrons in a copper atom.
The number of valence electrons can be determined by writing the electron configuration.
We can look up the periodic table for the atomic number of Cu. Z = 29.
Electronic configuration is written in a way that electrons fill the orbitals with lower energies first before filling orbitals with higher energies.
The sequence of orbitals for electron configuration can be seen from this diagram.
How many valence electrons does Cu have?