San Francisco seems far away---both in terms of geography and time. I will go there in March 2011 for the ASCD annual conference. The last time I was there was 1996 and that was for a conference, too: the NSTA International Conference for Science Education. It was the first time I ever presented anything. While I can say without a doubt that my presentation skills sucked, the material itself was good.
I developed this tool to use with my 9th grade Physical Science students. Part of the curriculum required them to learn to construct chemical formulas. Some of the kids cottoned onto the concept right away---others struggled. The course was one semester long, so I had two opportunities a year (x several preps a day) to figure out how to teach this. I also noticed that students in the fall had a more difficult time of things than my spring bunch. Whether that was due to growth spurts of frontal lobes or other factors, I'll never know. I do know that the "concrete" method I created to help them understand the concept worked. Here is what I did...
Each student had a packet of little squares of paper like these:
Each one had the name of the element and its chemical symbol. Those which had ions with a positive charge had a black dot at the bottom: one dot per charge. For example, Hydrogen and other elements in Group 1 all had one dot at the bottom; Magnesium, Calcium, et al. had two; Aluminum three; and so forth. The common transition elements that we used which had more than one oxidation state (e.g. copper, iron) had more than one tile available. Elements that formed negatively charged ions (like Oxygen) had holes punched at the top, one per "space" available for an electron to fill.
I could then ask students to write a formula using Hydrogen and Oxygen. Using their pieces, they would end up with something like this:
All they had to do at this point was transfer what they saw into the written formula, with elements at the top first: H2O. Eventually, I would wean students away from using the manipulatives as their understanding of oxidation states increased along with their understanding of the periodic table. I called this system "Elementiles."
There were limitations with using these, of course. They didn't help students directly connect atomic structure with why there were dots and holes on the pieces. But for kids who were already struggling to picture an atom they would never see, holding something in their hands was a helpful scaffold. And since every student had them at their desks (whether or not they needed them), there was no stigma in pulling out the Elementiles for help.
In March, it will have been close to 15 years since this first presentation. I have different material this time...new tools...and far better communication skills. Here's hoping I make the most of this golden state.