1.1 Electricity and the Electron
Today's module is on "Electron Movement."
Here are the bullet points to remember from the second module:
- Protons are said to have a positive charge and electrons a negative charge.
- Like charges repel; opposite charges attract.
- So the negative electrons are attracted to the nucleus by the positive protons. 
- The neutron has a neutral charge.
- In an atom like copper (which in its neutral state has 29 electrons), some electrons are closer to the nucleus than others.
- The outermost electrons are sometimes knocked out of an atom. What's left of the atom then becomes a charged "ion" (because it has lost some negative).
- The process of becoming an ion is called "ionization" and the amount of energy necessary to cause ionization is called the "ionization potential."
- The random drift of "free electrons" in a wire doesn't do anything. They need to be pushed.
 The electromagnetic force between these charges helps keep the atom together. Another force, the "strong nuclear force" keeps the protons together, even though their charges should repel them. The strong nuclear force only works over a very short distance, but it is stronger than the electromagnetic force that would otherwise push the protons apart.