General Chemistry I:  Structure and Energy

The order of topics in General Chemistry normally covered is very disjointed with students learning about reactions before they understand electronegativity.  The reason for this is to provide background for lab work.

During fall 2005, an "atoms first"  approach was used.  The semester started with electromagnetic radiation, then covered nuclear chemistry, and then atoms.  All of this required heavy emphasis on physics-related topics of energy, Coulomb’s Law, potential energy, and kinetic energy.  Molecular modeling was useful to calculate energy levels in atoms, to see the patterns and to use these in understanding electron configurations.  Atom properties (e.g. electronegativity) are all based on fundamental physics and were covered extensively.

This led to molecules and molecular structure followed by examination of energy considerations in making and breaking bonds.  This was a natural lead-in to the examination of both 1st and 2nd Laws of thermodynamics, since energy had been a consistent theme the entire semester (e.g. fusion and fission in nuclear chem, combustion in making and breaking bonds) [calorimetry and Hess’s Law were not covered].

The understanding of electronegativity and molecular structure was reinforced by several lessons to examine acid-bases properties and molecular structure (something the organic course does at the beginning in an very organized manner).  This briefly introduced equilibria and also required students to think in terms of energetics of negatively charged conjugate bases, resonance and inductive effects and Henderson-Hasselbalch considerations.

Liquids, solids, and some materials science was also covered to build on concepts of energy and structure that was the focus during first semester.  Gases were not covered at all since they didn’t fit, they are already covered in the two-semester physics course and represented material students already had learned in high school.

The semester ended with discussions of intermolecular forces and solubility, critically important topics that are central to much of second semester.

What was not covered during General Chemistry I were the exhaustive lessons on stoichiometry and many of the reactions.  Acid-base reactions and combustion reactions were examined at the end of the semester after the necessary background had been developed.  The time freed up allowed coverage of all of thermodynamics.  This made it possible to discuss solubility and vapor pressures of liquids from a thermodynamic basis and greatly enhanced the understanding of these while reinforcing the usefulness of thermodynamics.  Second Law implications of commercial power production were also emphasized.

Students needing background on lab activities will need to have those in the pre-labs from previous weeks.  The discussion of complex ions (normally taught second semester) was included in the course and deepened understanding of the lab on copper-ammonia complexes.

The course would be well served in the future from a lesson or two on lasers that could include Boltzman thermodynamic population levels.  Students need a sophisticated understanding of the types of EMR used, the molecular/atomic energy levels they correspond to, and an understanding for relevant thermodynamic equilibria for these states.