Atomic theory and bonding
In part one of this series, I described how switching between macroscopic, microscopic, and symbolic representations of concepts and theories can be confusing for students, especially for those still operating as dualist (right and wrong only), concrete operational thinkers. I also described the nature of scientific models, and the need to carefully identify their inherent limits.
During the data collection phase of research into the high school–university transition in chemistry, my attention was caught by one comment that quite literally stated, “Our high school teachers lied to us.”
In part 1 of this series,1 I described how different representations of concepts and theories can be confusing for dualist (“right or wrong”) and concrete operational students.
I’m not sure where I first saw this poster, but knew right away it would look great in a chemistry classroom. It captures each element’s unique spectrum, which demonstrates how these spectra can be used as a fingerprints to identify elements. Field Tested Systems created this poster to go along with its many products that allow students — and their teachers — to explore classroom gas-tube spectroscopy and astronomical spectroscopy.
The basic idea is that in any Lewis structure, all atoms (except hydrogen), whether single, double or triple bonded require eight valence electrons (VEs). Any valence electrons left over will have to be incorporated as lone pairs around the central atom. So all one has to do is count the number of valence electrons in the structure, subtract the number of valence electrons involved in a bonded atom, eight for all bonded atoms, according to the octet rule, except for H, which requires two.
