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Unformatted text preview: onded to the central atom, and only one H atom bonded to each O atom Formal charges: hypothetical charge an atom would have if bonding electrons are shared equally and lone pairs belong solely to single atoms total # of total # of valence electrons — nonbonding — in free atom electrons total # of
bonds – Use formal charges to determine the most plausible structure. – Minimize formal charges for molecules where the central atom can have an expanded octet. – Indicate any non‐zero formal charges for any atom in a molecule or polyatomic ion. Chapter 9: Molecular Geometry and Bonding Theories Valence‐Shell Electron Pair Repulsion (VSEPR) Model – repulsions between electrons determine molecular geometry or molecule’s shape – Predict the shape of a molecule using its Lewis structure. AB2 linear, 180˚ bond angle A=central atom, B=outer atom(s), AB3 trigonal planar, 120˚ bond angle E=lone pair(s) on central atom AB4 tetrahedral, 109.5˚ bond angle AB5 trigonal bipyramidal, 90˚ & 120˚ angles AB6 octahedral, 90˚ bond angle CHEM 161 Exam 4 Study Guide page 2 of 3 Chapter 9: Molecular Geometry and Bonding Theories (Continued) Variation on trigonal planar shape AB2E bent, <120˚ bond angle Variations on tetrahedral shape AB3E trigonal pyramidal, <109.5˚ bond angle AB2E2 bent, <109.5˚ bond angle Variations on trigonal bipyramidal shape AB4E see‐saw, <90˚ & <120˚ bond angles AB3E2 T‐shaped, <90˚ bond angles AB2E3 linear, 180˚ bond angle Variations on octahedral shape AB5E square pyramidal, <90˚ bond angles AB4E2 square planar, 90˚ bond angles Polarity • Use the shape and electronegativity differences to draw dipoles and determine if the molecule is polar or nonpolar • Recognize a dipole moment is a quantitative measure of a molecule’s polarity • Rank molecules in terms of increasing dipole moment Draw Lewis structures for othe...
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This document was uploaded on 03/22/2014 for the course CHEM 161 at Seattle Central Community College.
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