Title: Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals
1Chemical Bonding IIMolecular Geometry and
Hybridization of Atomic Orbitals
Chapter 10
2Valence shell electron pair repulsion (VSEPR)
model
Predict the geometry of the molecule from the
electrostatic repulsions between the electron
(bonding and nonbonding) pairs.
AB2
2
0
30 lone pairs on central atom
4VSEPR
AB2
2
0
linear
linear
AB3
3
0
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6VSEPR
AB2
2
0
linear
linear
AB4
4
0
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8VSEPR
AB2
2
0
linear
linear
AB4
4
0
tetrahedral
tetrahedral
AB5
5
0
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10VSEPR
AB2
2
0
linear
linear
AB4
4
0
tetrahedral
tetrahedral
AB6
6
0
10.1
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14VSEPR
trigonal planar
trigonal planar
AB3
3
0
AB2E
2
1
15VSEPR
AB4
4
0
tetrahedral
tetrahedral
AB3E
3
1
16VSEPR
AB4
4
0
tetrahedral
tetrahedral
AB2E2
2
2
17VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB4E
4
1
18VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB3E2
3
2
19VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB2E3
2
3
20VSEPR
AB5E
5
1
21VSEPR
AB4E2
4
2
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23Predicting Molecular Geometry
- Draw Lewis structure for molecule.
- Count number of lone pairs on the central atom
and number of atoms bonded to the central atom. - Use VSEPR to predict the geometry of the molecule.
What are the molecular geometries of SO2 and SF4?
24Dipole Moments and Polar Molecules
electron rich region
electron poor region
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27Which of the following molecules have a dipole
moment? H2O, CO2, SO2, and CH4
28Hybridization mixing of two or more atomic
orbitals to form a new set of hybrid orbitals.
- Mix at least 2 nonequivalent atomic orbitals
(e.g. s and p). Hybrid orbitals have very
different shape from original atomic orbitals. - Number of hybrid orbitals is equal to number of
pure atomic orbitals used in the hybridization
process. - Covalent bonds are formed by
- Overlap of hybrid orbitals with atomic orbitals
- Overlap of hybrid orbitals with other hybrid
orbitals
29How do I predict the hybridization of the central
atom?
Count the number of lone pairs AND the number of
atoms bonded to the central atom
of Lone Pairs of Bonded Atoms
Hybridization
Examples
2
sp
BeCl2
3
sp2
BF3
4
sp3
CH4, NH3, H2O
5
sp3d
PCl5
6
sp3d2
SF6
30Sigma bond (s) electron density between the 2
atoms
Pi bond (p) electron density above and below
plane of nuclei of the bonding atoms
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34Sigma (s) and Pi Bonds (p)
1 sigma bond
Single bond
1 sigma bond and 1 pi bond
Double bond
Triple bond
1 sigma bond and 2 pi bonds
How many s and p bonds are in the acetic
acid (vinegar) molecule CH3COOH?
35Delocalized molecular orbitals are not confined
between two adjacent bonding atoms, but actually
extend over three or more atoms.