# ABOUT SILICON

Metals conduct electricity because some of its electrons are free to move. In silicon, however, the electrons are all stuck tightly to the atoms and can't move. Consequently, pure silicon is pretty much an electrical insulator.
To make it conduct, we need to add a small amount of some other substance, a process called doping. If we add an element that provides some extra electrons, we get what's called an n-type semiconductor. It conducts electricity the same way that a metal does, by a flow of electrons.
How well it conducts depends on how much we dope it. Your workbench has tools for laying down two different grades of n-type semiconductor: N, which is lightly doped and has a fairly high resistance, and N+, which is more heavily doped and has a much lower resistance, almost as low as metal.