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Molecular Geometry and
Polarization
Shapes of Molecules
Valence Shell Electron Pair Repulsion Theory
(VSEPR)
a. Bonded electrons
b. Lone Pairs
1. Linear (180o)
BeH2
CO2
2. Trigonal Planar (120o)
NO3-
3. Tetrahedral (109.5o)
CH4
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4. Trigonal Pyramidal (~107o)
NH3
5. Bent (~104.5o)
H2 O
H
O
H
SO2
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6. Trigonal Bipyramid (120o, 90o)
PCl5
7. Octahedral (90o)
SF6
Shapes of Molecules
Ex: Multiple Bonds:
N2
H2CO
HCN
SO2
Shapes of Molecules
Models Activity
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SO22+
SO22SO2
SO3
SF3PF4XeCl5+
BrF4-
Predict the molecular geometry of:
WarmUp
SnCl3O3
SeCl2
CO32SF4
IF5
ClF3
ICl4-
ClF4SiCl3SO2
SCl4
SeO3
BrCl5
BrCl3
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Polar Molecules
1. Polar molecule – Overall, the
electrons are attracted more to one
end of an entire molecule
2. Non-Polar Molecule – The electrons
are spread out evenly over the entire
molecule
-/ + Partial (not full) charges
Electron Density
Examples:
H2
CH4
H2
H 2O
CH4
H2CO
H 2O
H2CO
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Polar Molecules
BeCl2
NH3
CO2
SO2
SF6
BCl3
CH2Cl2
Hybrid Orbitals
• A mixing of the atomic orbitals (s, p, d, f) of the
central atom
• Electrons no longer move in the old orbitals, but
in a new pattern
BeF2
Isolated Be
1s22s2 (Note that all
Be:
electrons are paired)
To bond Be must unpair some electrons:
Bonded Be
1s22s12p1
•Be•
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• Be is called an “sp” hybrid.
• Drawings:
Isolated Be
BeF2
CH4
Isolated C 1s22s22p2
Bonded C 1s22s12p3
Isolated C
Effect of Lone Pairs
• Lone pairs do count towards hybridization
• Ex: H2O
Bonded C
sp3
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Try BF3
Examples
CCl4
NH3
PF5
SF6
XeF4
BrF3
PH3
H2S
SF5SF4
CO32HCN
BrCl3
CH4
Hybrid Orbitals and Multiple Bonds
• sigma ( ) bonds – single bonds formed by hybrid
orbitals
• pi ( ) bonds – double or triple bonds, not formed
by hybrid orbitals
H
H–H
C=C
H
One
bond
H
:N=N:
H
One bond plus
one bond
One bond plus
two bonds
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• Consider C2H4
• Each C is sp2
• Double bond does not count
toward hybridization
• Consider C2H2
• Each C is sp hybridized
• Two bonds do not count toward hybridization
What is the hybridization and bonding types for
H2CO? Also, what are the bond angles?
Delocalized Bonding
What is the hybridization and bonding types for
acetonitrile (shown)? Also, what are the bond
angles?
• Adjacent multiple bonds can overlap.
• Benzene (C6H6)
• All bond lengths are equal
H
H - C -C=N:
H
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Use hybrid orbital theory to explain why all the
bonds in the NO3- ion are of equal length
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12 a) ~110o
b) BF3 flat (no lone pair)
21. a) (lin)lin b) (tetr)tr. Py c) (Trig bi)ss
d) (oh)oh e) (tetr)tetr
f) (lin)lin
22 a) (Tetra) Trig. Pyramid b) (Trig planar), Trig pl
c) (Tr. Bipy) T
d) (Tetra) Tetra
e) (Trig Bipy) lin
f) (Tetra) Bent
24 a) i) Octa (sq.planar) ii) Tetrahedral
iii) Trig Bipyr.(see-saw)
b) i) Two
ii) O
iii) One
c) S or Se
d) Xe
26. a) 104.5o, 120o
b) 109.5o, 120o
o
o
c) 107 , 104.5
d) 180o, 109.5o
o
28. 2 LP (NH2 , ~109 ), 1 LP (NH3, 107o), 0 LP (NH4+,
109o)
30. a) ClO2- (~109.5o, 2LP) NO2- (120o, 1 LP)
b) XeF2 (4 LP around the center)
32. a) Lone Pair on P
b) Lone Pair on center O
36. Polar = (b), (c), (e)
38.Ortho and meta
44. Not enough p suborbitals
46. SF2 = sp3, SF4 = sp3d
48. a) sp3
b) sp
c) sp2
d) sp3d
e) sp3d2
52. b) N2H4 (sp3), N2 (sp) c) N2 stronger bond
54. a) sp3 (C-H), sp2 (C-O) b) 36 ve c) 26 ved) 2 ve- in double e) 8 ve- in lone pairs
56. a) 1, 120o 2, 120o 3, 105o
b) sp2, sp2, sp3
c) 21 bonds
62.
100. In2S (I) [Kr]5s24d10
InS (II) [Kr]5s14d10
In2S3 (III) [Kr]4d10
In(III) is smallest (least mutual electron
repul)
In(III) has the highest lattice energy
102.a) C2H3Cl3O2
b) C2H3Cl3O2
c) Structure CCl3CH(OH)2
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