Consider we have very precise equipment (s) needed for this question. There's a finitely big uncharged conducting sphere. Suppose we had an extra electron from an external source and we plan to keep it on the sphere. Then how would that one electron arrange itself on the sphere? Where would it be placed?
I'm aware of the fact that the net electric field inside a conductor is zero. Considering it to be very basic I don't need a proof for that. If there would be 2 or more electron it's very easy to think about how would they align themselves in order to cancel the net electric field at any point inside the conductor. But when there's only one electron it's hard to imagine.