 In this video we're going to learn about the differences between chemical structures of a conductor and a non-conductor. This will be used to explain why different solids do and do not conduct electricity. Metallic solids are called conductors. Can you name a few metals found in wires? Pause the video and continue when you are ready. The correct answers often include copper, silver and gold. The latter two are not used often because they are very expensive. There are other metals that you could have listed. If you look closely at the structure of copper, it has a positively charged lattice of metal atoms surrounded by loosely held valence electrons. This is a bit like the covering of a pie, except the lattice that's on the top would extend all the way through. The loosely held electrons are free to move randomly in a metal, but once a battery or source of voltage is applied, the electrons flow in one direction, generating an electric current in the metal. Some materials offer hardly any electrical resistance to the flow of current or the movement of these electrons. These include some pure metals and metal oxides, called to a few degrees above absolute zero. There are special conductors called superconductors. Some non-metal conductors like graphite, a form of pure carbon, or solutions of salts forming electrically charged ions will conduct electricity, but these have more resistance. Most other solids have tightly held valence electrons, which may be locked up in chemical bonds. Some examples include solid salts, ionic substances like sodium chloride, sulfur, an element, polythene of polymer, and glass. The electrons in these examples are not free to move, and so are non-conductors. What is the other term used to describe a non-conductor? The correct answer to describe substances that do not readily conduct heat or electricity is an insulator. Did you get it right? Here's a challenge. How can you get an electric shock? You, after all, are an insulator. Pause the video and think about this. When you're ready, please continue. The answer is that an electric shock occurs when electricity source, with a large voltage, causes sufficient current to enter and exit the human body through the skin, muscles, or hair, all insulating materials. In summary, metals contain lattices of positively charged ions. The electrons are loosely held and are free to move between the metal atoms. When a voltage is applied, a current is able to flow. Some materials, like pure metals and some metal oxides, when supercooled, are exceptionally good conductors. These are superconductors. In an insulator, the electrons may be more tightly bound to the atom, or held in a bond or bonds. This makes them less mobile, and so the electrons are not as free to move. These materials act as insulators. Examples include most nonmetals, solid ionic substances, plastics, you and me.