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Unformatted text preview: Chem 120A More QM in chemistry, time-independent Schr¨odinger equation 09/01/10 Fall 2010 Lecture 3 Other reasons for quantum mechanics in chemistry • Quantum mechanics is needed to justify ad hoc explanations of behavior of molecules. – Atoms: old quantum theory does not successfully describe the structure of non-hydrogenic atoms (multiple electrons in bound states) * For large atoms, the electron configuration doesn’t depend on a single quantum number – Old quantum theory only dealt with periodic motion, so what about other types of motion? – Stability of chemical bonds ( i.e. formation of molecular orbitals) comes from “exchange forces,” which are described with quantum mechanics Figure 1: From www.chem.ucalgary.ca – why is the picture of two balls in the bottom of the potential well wrong? – Octet rule and VSEPR (successful rules for molecular bonding and structure) need physical explanation (QM provides this in the form of superposition of atomic orbitals) – Some properties of atom/molecules (...
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- Fall '10
- CHEM 120A, Schr¨ dinger equation