10-Covalent Bonds - 5.111 Lecture Summary #10 September 30,...

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5.111 Lecture Summary #10 September 30, 2009 10.1 Reading for today: 2.14-2.16, 2.5 Reading for Lecture 11: Sections 2.7,2.8 COVALENT BONDS 0 3056 r e =0.74Å Δ E d H + H 2624 r ENERGY OF INTERACTION kJ/MOLE H H r ENERGY OF INTERACTION = NUCLEAR-NUCLEAR REPULSION + e – NUCLEAR ATTRACTION + e –e REPULSION e 2 4 π ε 0 r electron interaction Energy of molecule includes potential and kinetic energies Electron kinetic energy in molecule is less than in atom! Why? Uncertainty principle: ∆ݔ∆݌ ൒ Ñ /2 says that smaller spatial region (smaller Δ x) means larger uncertainty in momentum (larger Δ p) which also means larger minimum momentum larger kinetic energy So kinetic energy of electrons is a lot lower in the molecule than the atom This is a big part of the bonding energy, in addition to the potential energy ++ A b –– a b H H e
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5.111 Lecture Summary #10 September 30, 2009 10.2 LEWIS DIAGRAMS 20 years before quantum mechanics - G. N. Lewis - key to bonding was sharing of 2 e s, one from each atom.
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10-Covalent Bonds - 5.111 Lecture Summary #10 September 30,...

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