01:160:161 Lecture Notes - Lecture 6: Valence Bond Theory, Lewis Acids And Bases, Chemical Bond
12 Dec 2018
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Document Summary
Lewis theory (and structures) does not give good numerical predictions regarding bond lengths and energies. Lewis theory gives good approximations of bond angles for a molecule but can"t account for actual bond angles for many molecules. Molecules showing resonance are not adequately dealt with in lewis theory. There are other bonding theories that improve upon loewis theory and can explain things that lewis theory cannot. A chemical bond is the overlap between two half-filled atomic orbitals. The orbitals are necessarily in the valence shell. The electrons in the orbitals must have paired spins. The amount of orbital overlap between atoms represents an energy minimum and a balance between electron nucleus attraction + nucleus nucleuc repulsion. The geometry of the overlapping orbitals determines the shape of the molecule. An issue with methane and valence bond theory. Valence bond theory does not adequately account for certain attributes of ch4. C readily makes 4 identical bonds with h.
