electrostatics - How much electric charge can a copper sphere, made of N atoms, contain?

If somebody wants to charge a cooper sphere made of N atoms, what is the maximum positive charge the sphere can reach? Same question about a negative charge.

Source

For example if the sphere is small, made of 100 - 1000 atoms, can all atoms remain without the electron on the last layer or even without some electrons from the deeper layers?

Note: The indicated answer is for the case when someone wants to charge the sphere with a negative charge and it contain just a qualitative explanation.