Formal_charge - 1 2 Carbon Dioxide, CO2 Carbon Dioxide, CO2...

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Unformatted text preview: 1 2 Carbon Dioxide, CO2 Carbon Dioxide, CO2 Formal Atom Charges Formal Atom Charges • Atoms in molecules often bear a charge (+ or -). • The predominant resonance structure of a molecule is the one with charges as close to 0 as possible. Partial Charges in CO 2 6 - (1/2)(4) - 4 = 0 • Formal charge = Group no. - 1/2 (no. bond electrons) - (no. of LP electrons) •• • • O •• C O • • Yellow = negative & red = positive red Relative size = relative charge 4 - (1/2)(8) - 0 = 0 Thiocyanate Ion, SCNIon, 4 •• • • •• • • S •• S •• C N •• C N • • 4 - (1/2)(8) - 0 = 0 5 Thiocyanate Ion, SCNIon, 5 - (1/2)(4) - 4 = -1 6 - (1/2)(4) - 4 = 0 3 • • S • • • • S C C •• N Partial Charges in SCN- • • •• N • • •• Which is the most important resonance form? Page 1 6 All atoms negative — but most on the S 7 Boron Trifluoride, BF3 Boron Trifluoride, BF3 •• • • •• • • F •• F • • • • •• B • • F •• • • F •• • • F • • B • • F 8 Partial Charges in BF 3 +1 -1 • • •• What if we form a B—F double bond to satisfy the B atom octet? F is negative and B is positive Page 2 ...
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This note was uploaded on 10/19/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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