1. It seems to me that, for most high school students, chemistry should probably start with things that can be observed and then move to explain them with theory you can't observe. So you can observe many elements. You can observe chemicals. Atoms? Not so much. You can observe gases, liquids, and solids. Covalent bonding, a little harder.
2. For whatever reason, I am really attracted to teaching chemistry from the periodic table. I know it has to do with my personality. I remember things far better if I can see the big picture first. Start with individual details and half of them will evaporate away for me.
The periodic table is like a map. Again, my memory and understanding works better if you approach learning with a spiraling circle. Start with the big picture. Then swirl around the land again in more detail. Then start swirling around the subtopics in the same way. Since there is limited time, don't teach any one area exhaustively before moving on to the next. If you do that, I will know half the topics well and know nothing about the other half.
Some topics in math and science are cumulative, but many aren't. I think you could start with motion, thermodynamics, or electromagnetism in physics, for example. But, inevitably, high school and college students like me end up with a lot of knowledge of motion and very little of electromagnetism. I don't think I had a history class in high school that got beyond World War I. And the surface area or volume of a sphere--I was never in a math class that got that far, even though you could go do a web search and learn it right now.
So I prefer swirling. Go over the whole field in the broadest of strokes. Then go through all the major topics again in greater detail. Then in later courses go into the individual topics in great detail.
3. Another way to teach, and one that would fit with yet another personality, is to start small and go big. You could start with the atom. Then move to molecules. Then move to organic chemistry. Then organelles, then cells. Then move to tissues, organs, systems. Then motion, sociology, eventually astronomy.
4. So in conclusion, how's this for a chemistry curriculum?
- Start as usual by distinguishing mixtures from homogeneous material... compounds, elements. Do it with actual stuff. Goal--to show that all the stuff around us boils down to some basic components and combinations of components.
- Now move to the periodic table. These are the elements. All matter around us reduces to these. Run through it with object lessons. Some are gases, some liquids, some solids at room temperature. Some are more stable than others. Look, here's a helium balloon. Here's a lithium battery.
- You can combine them together and make compounds. Salt. The oxygen in the air comes in pairs of two oxygens. Etc...
- With hydrogen you can dive into what an atom is. What is the default state of an atom? How do atoms take on charges? How do you get hydrogen chloride (ions)? What are acids?
- You can do some experiments too. Use electrolysis to isolate hydrogen and oxygen, for example.
- With helium you can introduce the noble gases and go down into Neon, Argon, etc. Now comes the octet rule and an explanation of why these are so stable.
- I think you could cover a good deal of the basics in a short time in this way. Atomic mass, metals, alkali metals, semiconductors, precious metals, radioactive elements. Mention types of bonding, electronegativity, etc but save depth explorations for later.
- But before long, you will want to begin looking at reactions. Now we're balancing equations. Now we start looking at energy and heat. For whatever reason, these aspects of chemistry seem harder for people to get their heads around, but we've now been amply prepared for them.
- Show the reactions, show the experiments. To the extent it's practicable, have students do the experiments.
- Repeat in greater depth...
But that's for another day...