CHMA10H3 Lecture 21: Resonance Structures
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CHMA10H3 Full Course Notes
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Lewis structures: resonance structures, some molecules cannot be represented accurately by a single lewis structure, e. g. Ozone, o3: problem: both o-o bonds are actually the same length, the real structure is a hybrid of the two structures, misconception about resonance. Molecules do not oscillate between different resonance structures; rather, each molecule is a hybrid (or composite) of its resonance structures: resonance and formal charges. One of more resonance structures may contribute more to the overall hybrid structure. Resonance structures can easily be drawn by a technique called electron pushing : e. g. The three major resonance contributors of co3 -2: octet rule exceptions: odd number of electrons. Most odd-electron species are high in energy and unstable. Expanded octet only for third row or lower (e. g. sf6: occurs when no other choice, alternate structures has excessive formal charges. Application: radical traps: high energy of radicals can lead to runaway reactions. Implications for food spoilage; human health: defend using radical traps.
