A post about teaching science!
A word of warning to those who have advanced degrees in science and cannot bear the simplification that happens when we introduce new ideas to 11-year-olds: this is probably not a post you want to read. Much has been simplified, left out, etc. They're 11. It's groundwork.
I had a good moment today.
I've been teaching the sixth graders about electron shells, trying to give them just enough so that they understand ions and bonding, but not so much that we get lost in the land of abstraction. We "learned" about electron shells in middle school science when I was a kid, but I'm pretty sure I didn't really get it until high school. I want to keep it simple, yet give them some real content to chew on at the same time. I've taught this before, once, and got a little bogged down. I wasn't sure how to sequence atomic structure, bonding, mixtures & solutions, chemical reactions, and so forth. I still don't, but I'm getting closer to knowing.
I've been taking them through a series of mini-lessons and practice worksheets. They like it, because it seems really hard at first and then turns out to be pretty easy (that's how I know that I'm close to knowing how to do this right). At the same time, a few kids have melted down when the going got tough, not trusting me to lead them safely through it or their own ability to grapple with hard ideas successfully.
We learned about energy levels, and how they get filled with electrons. I'm trying to keep in the back of their heads the idea of the electron cloud, constant and somewhat unpredictable motion, so they don't walk away thinking electrons sit in pairs in little loveseats surrounding the nucleus of an atom.
After that, I had them complete a table where they drew electron dot diagrams for a bunch of different elements. I slyly listed the elements in order in the table by element group/family, so they did hydrogen, then lithium, then sodium, then beryllium and magnesium, and so on. They got pretty good at drawing electron dot diagrams.
From there, I asked them to look at the different groups on the periodic table. They figured out how many electrons each group had in its outer shell, and how many it would need to become stable. Stable is a complicated idea to explain on your way to ionic bonds.
So at this point, we have a big table on the board, listing each group, how many electrons it "has" and how many it "needs."
Remember a few days ago, when we found out about the properties of elements in different groups? Do you remember that there were two groups where the atoms liked to bond with each other? Which groups were those? We'd focused on the noble gases, alkali metals, and halogens, and only briefly touched on the other groups. Okay, can anyone look at this chart and come up with an idea about why atoms in those two groups might be able to join with each other really easily?
There was a pause, and then a few kids got it. I mean, seriously, we are talking about little cartoon lightbulbs going on over their heads. That one has 1 and needs 7, and this one needs 7 and has 1!
Oh, yeah. That's really interesting. Look at the table again. Does anyone see any other groups that might be able to work something out with each other?
And suddenly, a whole lot of lightbulbs went on. Ohhh!
It was cool.