2. Force Laws, Lewis Structures and Resonance
Richard M. Colgate Professor of Chemistry
This lecture investigates the quest for a chemical force law, contrasting Hooke's and Coulomb's laws with the Morse potential. It then introduces G. N. Lewis's shared-pair model, Lewis-dot notation, and the concept of resonance to describe molecular structure and reactivity.
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."
1. How Do You Know?
Next · Lecture 33. Double Minima, Earnshaw's Theorem and Plum-Puddings