2. Force Laws, Lewis Structures and Resonance 

Freshman Organic Chemistry (CHEM 125)
Professor McBride begins by following Newton's admonition to search for the force law that describes chemical bonding. Neither direct (Hooke's Law) nor inverse (Coulomb, Gravity) dependence on distance will do - a composite like the Morse potential is needed. G. N. Lewis devised a "cubic-octet" theory based on the newly discovered electron, and developed it into a shared pair model to explain bonding. After discussing Lewis-dot notation and formal charge, Professor McBride shows that in some "single-minimum" cases the Lewis formalism is inadequate and salvaging it required introducing the confusing concept of "resonance."
00:00 - Chapter 1. Newton's "Additions": An Inquiry into Small Forces
09:15 - Chapter 2. Is there a Chemical Force Law?
18:26 - Chapter 3. The Morse Potential
21:42 - Chapter 4. What are Bonds? Early Understandings of Valence
32:52 - Chapter 5. Deriving Structure and Reactivity from Valence Electrons
Complete course materials are available at the Open Yale Courses website: open.yale.edu/c...
This course was recorded in Fall 2008.