chem notes 11-19

chem notes 11-19 - -all 3 are equal in strength/length...

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November 19, 2007 Dr. Stevens Gen. Chem. 1 Lewis Structures -octet rule ionic (+/-) covalent ( – )/( •) Resonance Structures : multiple Lewis structures needed to represent full/covalent bonding -ex: structure 1  structure 2  structure 3 -double-headed arrows connect all needed Lewis structures -ex: SO2 •• ••O•• – ••S = O•• ••  •• ••O=S•• – ••O•• •• -no flicker/alternating happens -exists as hybrid in b/w the 2 structures Strength and length of bonds -S ----- O = 1 -S =--=--=O = 1.5 -S=O = 2 -S=--O = 3 -in carbonate, avg. strength of a C-O bond is 4/3 similar to 1 ½
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Unformatted text preview: -all 3 are equal in strength/length Exceptions to the Octet Rule-incomplete octet: (usu) central atom (can be any atom) has less than 8 e- (even#)-ex: H2 = H H -ex: BF3 = Boron ONLY gets 6-odd # of electrons: one atom will have an odd # of e- instead of 2/8-ex: CN (carbide)-C=_N-carbon has 7 e--some atom (usually central) has more than 8 electrons (10, 12, 14, etc.)-n=3 end: can expand octets can expand into d-n=1 n=2: cannot expand only s&p-ex: OF6 v. SF6-SF6 can expand (12 e- on S)-OF6 cannot exist...
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