C121 11-3 lec23GL

C121 11-3 lec23GL - Lecture 23 November 2, 2011 Bonding:...

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Unformatted text preview: Lecture 23 November 2, 2011 Bonding: Specific Models Last Day: Models of Bonding I Localized Electron Bonding Models (i) Lewis Structures Rules, Formal Charge, and Exceptions Today: Models of Bonding I Localized Electron Bonding Models (i) Lewis Structures Rules, Formal Charge, Exceptions, Resonance (ii) Valence Shell Electron Pair Repulsion Theory (ii) Hybrid Atomic Orbital Theory II Molecular Orbital Theory I Localized Electron Bonding Model (i) Lewis Structures 2-D diagram showing the arrangement of valence electrons around atoms in a molecule driving force is that atoms try to achieve noble gas electron configurations (octets, or duet for H) in forming stable molecules Rules for Drawing Lewis Structures 1. Determine the total the number of valence (outer shell) e- for each atom in the molecule recall group # = # valence e- on atom 2. Form single (2e- ) bonds between the central atom and the outer atoms. Subtract these electrons from the total number of valence electrons typically the central atom is the least electronegative atom in the molecule (ie. it is the atom which most wants to share its electrons); H cannot be the central atom 3. With the remaining electrons, complete the octets of the atoms bonded to the central atom using pairs of electrons (a.k.a lone pairs) : H only needs a duet. Subtract these from the total valence e- . 4. Use the remaining electrons to complete the octet of the central atom. If there are not enough e- to do so, use lone pairs of e- on the outer atoms to form multiple bonds until the central atom has achieved its octet. Formal Charge A Method for Finding the Best Lewis Structure each neutral atom has a characteristic # of valence e...
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This note was uploaded on 12/10/2011 for the course CHEM 121 taught by Professor Leech during the Fall '11 term at Simon Fraser.

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C121 11-3 lec23GL - Lecture 23 November 2, 2011 Bonding:...

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