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I II III
Molecular Geometry
(p. 232 – 236)
Ch. 8 – Molecular Structure
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A. VSEPR Theory
Valence Shell Electron Pair Repulsion Theory
Electron pairs orient themselves in order to minimize repulsive forces
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A. VSEPR Theory
Types of e- Pairs Bonding pairs – form bonds Lone pairs – nonbonding e-
Total e- pairs– bonding + lone pairs
Lone pairs repel
more strongly than bonding
pairs!!!
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A. VSEPR Theory Lone pairs reduce the bond angle
between atoms
Bond AngleBond Angle
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Draw the Lewis Diagram Tally up e- pairs on central atom (bonds + lone pairs)
double/triple bonds = ONE pair Shape is determined by the # of bonding pairs and
lone pairs
Know the 13 common shapes & their bond angles!
B. Determining Molecular Shape
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C. Common Molecular Shapes # 1
2 total
2 bond
0 lone
LINEAR180°
BeH2
→ Electronic Geometry = linear
Hybridization = sp
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3 total
3 bond
0 lone
TRIGONAL PLANAR
120°
BF3
C. Common Molecular Shapes # 2
→ Electronic Geometry = trigonal planar
Hybridization = sp2
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C. Common Molecular Shapes # 33 total
2 bond
1 lone
BENT
<120°
NO21-
→ Electronic Geometry = trigonal planar
Hybridization = sp2
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4 total
4 bond
0 lone
TETRAHEDRAL
109.5°
CH4
C. Common Molecular Shapes # 4
→ Electronic Geometry = tetrahedral
Hybridization = sp3
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4 total
3 bond
1 lone
TRIGONAL PYRAMIDAL
107°
NCl3
C. Common Molecular Shapes # 5
→ Electronic Geometry = tetrahedral
Hybridization = sp3
<109.5°
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4 total
2 bond
2 lone
BENT
104.5°
H2O
C. Common Molecular Shapes # 6
→ Electronic Geometry = tetrahedral
Hybridization = sp3
<109.5°
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5 total
5 bond
0 lone
TRIGONAL BIPYRAMIDAL
120°/90°
PI5
C. Common Molecular Shapes # 7
→ Electronic Geometry = trigonal bipyramidal
Hybridization = sp3d
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5 total
4 bond
1 lone
SEESAW
<120°/<90°
SF4
C. Common Molecular Shapes # 8
→ Electronic Geometry = trigonal bipyramidal
Hybridization = sp3d
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5 total
3 bond
2 lone
T-SHAPE
<90°
ClF3
C. Common Molecular Shapes # 9
→ Electronic Geometry = trigonal bipyramidal
Hybridization = sp3d
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5 total
2 bond
3 lone
LINEAR
180°
I31-
C. Common Molecular Shapes # 10
→ Electronic Geometry = trigonal bipyramidal
Hybridization = sp3d
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6 total
6 bond
0 lone
OCTAHEDRAL
90°
SH6
C. Common Molecular Shapes # 11
→ Electronic Geometry = octahedral
Hybridization = sp3d2
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6 total
5 bond
1 lone
SQUARE PYRAMIDAL
<90°
IF5
C. Common Molecular Shapes # 12
→ Electronic Geometry = octahedral
Hybridization = sp3d2
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6 total
4 bond
2 lone
SQUARE PLANAR
90°
KrF4
C. Common Molecular Shapes # 13
→ Electronic Geometry = octahedral
Hybridization = sp3d2
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SeO3
3 total
3 bond
0 lone
D. ExamplesO
O Se O
E.G. = TRIGONAL PLANARM.G. = TRIGONAL PLANAR
120°Hybridization = sp2
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AsH3
4 total
3 bond
1 lone E.G. = TETRAHEDRALM.G. = TRIGONAL
PYRAMIDAL
107° (<109.5°)
H As HH
D. Examples
Hybridization = sp3
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E. Hybridization
Provides information about molecular bonding and molecular shape
Several atomic orbitals mix to form same total of equivalent hybrid orbitals
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E. Hybridization
Carbon is common example (orbital diagram)
One of 2s electrons is promoted to 2p 4 identical orbitals form sp3 hybridization
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E. Hybridization Other types of hybridization
BeH2 forms
AlCl3 forms
SiF4 forms
KrF4 forms
SF4 forms
Remember the superscript is the orbital, not e-
configuration!
exceptions
sp
sp2
sp3
d2sp3 or sp3d2
dsp3 or sp3d
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F. Hybridization Example Compare shapes and hybrid orbitals:
PF3 PF5
E.G. Tetrahedral Trigonal bipyramidal
M.G. Trigonal pyramidal Trigonal bipyramidal
HYB sp3 dsp3