This part from University Physics turned my world upside down. What is the difference between ions, free electrons, and excess charge? Also, ions and free electrons make up a neutral conductor? Bloody how?
In practical problems we often encounter situations in which we want to know the electric field caused by a charge distribution on a conductor. These calculations are aided by the following remarkable fact: When excess charge is placed on a solid conductor and is at rest, it resides entirely on the surface, not in the interior of the material. (By excess we mean charges other than ions and free electrons that make up the neutral conductor.)