Electricity - Atoms and Molecules - Teacher's Notes  
The Greek word electrum meant amber (fossilized pitch). When rubbed with animal fur, amber gains a static electrical charge. Over the years, the word electrum gradually came to refer to the electrical charge rather than to the amber itself.
The Difference Between Electricity and Electronics
Obviously the words "electron", "electricity", and "electronics" are closely related. For historical reasons, we divide the science and engineering of electrons into two parts; electricity, and electronics. Electricity is the domain of motors, light bulbs, generators, and other "large scale" items. Electronics has come to mean the domain of vacuum tubes, transistors, integrated circuits, and other "small scale" items. We're covering electricity theory and practice here, because it is an important sub-set of electronics that can be dealt with as a stand-alone topic.
Electron Orbits
In the 1920's we thought that individual electrons had individual orbits around the nucleus of an atom. We have come to realize that orbits are not a very meaningful concept for electrons. We now describe electrons as existing in a "cloud" that surrounds the atomic nucleus. At any given instant, an electron has some statistical likelyhood of being somewhere in that cloud. That is about all that we can say!
Questions for your students:
Q: What are the building blocks of nature?
A: Atoms. (an OK answer, but we were hoping for something else) There are only 100+ types of atoms. (See the periodic table of the elements) The behaviors of individual atoms do not explain the behaviors of natural substances. For example, atoms by themselves are neither conductors nor insulators. In fact, atoms don't even exist by themselves. They pretty much always combine together into molecules.
A: Molecules. There are millions of different molecules. The relationships between the atoms inside of each molecule cause the molecule to have very interesting characteristics. For example, some molecules are insulators, some are conductors. (See the next page)

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