Lec' 9 Lewis Dot Structures

1
Fred J. Grieman
Lec. 9 Lewis Dot Structures Group
Valence Electrons L.D. for Atoms
L.D. for Molecules
Ions Covalent molecules
Multiple bonds Resonance
Structures Formal Charge
Valence Shell Expansion HW 3 17, 23, 27,
29, 33, 39, 41, 47
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Periodic Table
Metals Lose e-s easily
Non-metals Gain e-s easily
Transition metals (lose e-s easily)
Metalloids Tend to both lose and gain e-s
Valence Electrons ____________________________ Co
re Electrons Inner electrons that give
electro-neutrality ___________ indicates of
___________________ Symbolize with Lewis Dot
Structures
N O N R E A C T I V E
Electronegativity measure of atoms power to
attract an
electron when it is in a molecule
3
Group indicates of valence electrons
Symbolize with Lewis Dot Structures
Exception!!!
H
He
B
C
O
Li
Be
N
F
Ne
Mg
Si
S
Cl
P
Ar
Al
Na
I
VIII
II
III
IV
V
VI
VII
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Molecules Lewis Dot Structures Noble Gas
Octet Rule - Why? __________________ (Will
see from Quantum Mechanics.) Not Magic of
Octet !!! or magic stability of noble gas.
(H exception - Full valence is duet, not
octet) Ionic compounds Alkali and Alkaline
Metal lose valence e-s to become
____________

w/ noble gas configurations Halogens and
Chalcogens (in rxn with them) gain e-s to
become ____________

w/ noble gas configurations Demonstr
ation Lewis Dot Structure predicts correct ionic
compounds (Again, Ionic compounds are
lattices, not individual molecules) Name
cation anion
______________________
__________________________
__________________________ Examples
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Covalent Compounds Nonmetal nonmetal ?
compound
(not
ions!!!) Why form? ? octet, but
how??? Share electrons ?
________________ Demonstration Text
Example Hydrogen Chlorine to form Hydrogen
Chloride (not Hydrochloric Acid !!!)
2 e- covalent bond Both have Noble
Gas Configuration
Bonding Pair


____________ Examples
H
Cl ?
6
F2 F 7 valence e-s, needs 1 e-, but
cant be transfer, must share!!
Both have Ne configuration
O2 6 valence e-s, needs 2
Again, both have Ne configuration
O
O
Is double bond real? O ? O more e-s btwn
nuclei nuclei attracted to e-s ? stronger
bond?? YES!! Experiment
_____________________________ N2 ???
Experiment - ____________________________________
Triple bond shown on Board.
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• Text Method for Lewis Dot Structures
• A Total of Valence Electrons
• 2) N of e-s for all noble gas configs.s
• 3) S N A Shared Pairs
• 4) 2 Bonding e-s btwn each atom
• 5) Bonding e-s remaining ? double /or triple
  bonds
• 6) Remaining e-s are lone pairs
• ________________________
• Hybrid of all equivalent structures. Multiple
  Bonds DO NOT hop around
• ________________________
• 1) F.C. on atom ( l.p. e-s ½ s.p. e-s
  G. )
• 2) Reduce F.C. with multiple bonds when allowed
  (lowest F.C. is best)
• 3) F.C. on more electronegative atom F.C.
  on more electropositive atom
• 4) Check S F.C. molecules charge
• _______________________ Great than octet okay
  for 3rd Row