10-31-07%20-%20Lecture%2011%20-%20Chapter%202

10-31-07%20-%20Lecture%2011%20-%20Chapter%202 - actinides...

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Why are formal charges useful? In general, Lewis structures written to have FC on each atom as close to 0 as possible Most stable bonding arrangement If formal charges arise, try to minimize
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Formal Charge (FC) Formal charge measures how many electrons each atom “owns” Useful determining if Lewis structure is reasonable Formal Charge (FC) = V – (L + S/2) V = # of valence electrons L = # of lone pair electrons S = # of shared electrons Sum of FC on atoms in neutral molecule is 0 Sum of FC on atoms in ion is charge on ion
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Exceptions to the Octet Rule 1. Hydrogen (duet rule) 2. Radicals (odd number of electrons) O 3. Expanded valence shell molecules PCl 5 , SF 6 4. “Electron deficient” molecules BF 3 5. Lewis diagrams don’t work for transition metals and
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Unformatted text preview: actinides Electron Deficient Electron Deficient Less than full octet can occur for Group 13 compounds: B and Al These atoms are sufficiently small that four bonds are quite crowded. BF 3 Lewis Acid/Bases Lewis Acid: an electron pair acceptor BF 3 Lewis Base: an electron pair donor F Is a particular bond ionic or covalent? Rephrase: Are electrons being shared equally? If equally shared, the bond is a covalent bond with no ionic character Equal sharing occurs ONLY between homonuclear diatomics So what about the vast majority of bonds that occur between different atoms? Electronegativity Electronegativity...
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This note was uploaded on 10/24/2009 for the course CHEM 234234234 taught by Professor Johnson during the Fall '08 term at UCSD.

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10-31-07%20-%20Lecture%2011%20-%20Chapter%202 - actinides...

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