Third grade is a reasonable time to start teaching the structure of atoms. I say this because it’s exactly what I did in 4 lessons over the course of a month for the third-grade class at a local grammar school in Silver Spring, Maryland.
I began the lessons by explaining that everything in the world is made up of atoms, and that atoms themselves are made up of central nucleus surrounded by tiny electrons circling around them.
We’ve all experienced electrons, because electrons are what’s flowing through electrical wires and turning on our lights, radios, and TV’s, cooling our refrigerator, and heating our electric stoves.
The reason electrons revolve around the nucleus, I explained, is that electrons have a negative electrical charge and the nucleus is made up of tiny protons that have a positive electrical charge, and positive and negative attract each other. Turning this around, 2 negative electrons next to each other repel each other and push away from each other.
To help clarify positive and negative, I brought in a van der Graaf generator and explained how it collects negative electrons on its globe and positive protons on its wand. To make sure the kids understood what the words “attract” and “repel” meant, I asked them to predict what would happen to their hair if they touched the globe of the van der Graaf generator and allowed electrons to flow onto their hair.
I then asked for any courageous volunteers to come up and touch the globe. The raucous reaction of the class watching the volunteer touch the van der Graaf generator and seeing her hair stand on end firmly established that negative electrons repel each other.
After that, I explained that while the dome of the van der Graaf generator was negative, the wand of the van der Graaf generator was filled with positive electrical charges. I then asked the class to predict that would happen if I brought the wand close to the dome of the van der Graaf generator.
When I did bring the wand of the van der Graaf generator close to the negatively-charged globe, the crackling lightning bolts between them was met with shrieking excitement, enough to firmly reinforce that positive electrical charges attract negative electrical charges.
The next step was explaining that everything in the world is make of atoms, and that every atom has a positive center called the “nucleus” surrounded by negative electrons revolving around the nucleus. The only reason negative electrons didn’t crash into the nucleus is because they’re revolving around the nucleus like a ball on a string.
Some atoms, I explained, have only 1 electron circling around the nucleus while other atoms have 2, 3, 4, 5, up to 100 electrons circling around the nucleus. I then asked if anyone had heard of oxygen, gold, silver, iron, and hydrogen, and used a simplified version of the periodic table which listed the number of electrons circling the nucleus in each atom.
The next step was explaining that atoms can bond together and when they do, they form a molecule. Water, for example, was made up of 2 hydrogen atoms bonded to an atom of oxygen. We know this because when chemists pull water molecules apart, the hydrogen atoms and oxygen atoms can be capture, which is the next thing we did with an electrolysis apparatus I brought to class.
A match held at the top of each column of the electrolysis apparatus produced a bright flame on the oxygen side and a popping “explosion” on the hydrogen side, which of course, excited the class no end. The lesson, I emphasized, was that we had pulled apart a molecule of water, which puts out fires, and yet each atom of the water molecule either created a fire, or added to a fire. The lesson they learned was that when 2 atoms bond together, the molecule that forms can be, and usually is, completely different from the atoms that bonded together to make the molecule.
The take-home message here is that grammar school students can be taught the structure of atoms, and then taught that atoms can bond to each other to form molecules with properties completely different from the properties of the individual atoms being bonded together.