ap ch 10 bonding ii
TRANSCRIPT
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Chemical Bonding II:
Molecular Geometry andHybridization of Atomic
OrbitalsChapter 10
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10.1
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Valence shell electron pair repulsion (VSEPR) model:
Predict the geometry of the molecule from the electrostaticrepulsions between the electron (bonding and nonbonding) pairs.
AB2 2 0
Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
10.1
linear linear
B B
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Cl ClBe
2 atoms bonded to central atom0 lone pairs on central atom 10.1
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AB2 2 0 linear linear
Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3 3 0trigonal
planar
trigonal
planar
10.1
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10.1
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AB2 2 0 linear linear
Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3 3 0trigonal
planar
trigonal
planar
10.1
AB4 4 0 tetrahedral tetrahedral
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10.1
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AB2 2 0 linear linear
Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3 3 0trigonal
planar
trigonal
planar
10.1
AB4 4 0 tetrahedral tetrahedral
AB5 5 0trigonal
bipyramidal
trigonal
bipyramidal
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10.1
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AB2 2 0 linear linear
Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3 3 0trigonal
planar
trigonal
planar
10.1
AB4 4 0 tetrahedral tetrahedral
AB5 5 0trigonal
bipyramidal
trigonal
bipyramidal
AB6 6 0 octahedraloctahedral
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10.1
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10.1
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bonding-pair vs. bonding
pair repulsion
lone-pair vs. lone pair
repulsion
lone-pair vs. bonding
pair repulsion> >
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3 3 0trigonal
planar
trigonal
planar
AB2E 2 1
trigonal
planar bent
10.1
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB3E 3 1
AB4 4 0 tetrahedral tetrahedral
tetrahedraltrigonal
pyramidal
10.1
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
AB4 4 0 tetrahedral tetrahedral
10.1
AB3E 3 1 tetrahedral
trigonal
pyramidal
AB2E2 2 2 tetrahedral bent
H
O
H
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
10.1
AB5 5 0trigonal
bipyramidal
trigonal
bipyramidal
AB4E 4 1
trigonal
bipyramidal
See-Saw(distorted tetrahedron)
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
10.1
AB5 5 0trigonal
bipyramidal
trigonal
bipyramidal
AB4E 4 1
trigonal
bipyramidal
See-Saw
AB3E2 3 2trigonal
bipyramidalT-shaped
ClF
F
F
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
10.1
AB5 5 0trigonal
bipyramidal
trigonal
bipyramidal
AB4E 4 1
trigonal
bipyramidal
See-Saw
AB3E2 3 2trigonal
bipyramidalT-shaped
AB2E3 2 3
trigonal
bipyramidal linearI
I
I
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
10.1
AB6 6 0 octahedraloctahedral
AB5E 5 1 octahedralsquare
pyramidal
Br
F F
FF
F
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Class
# of atoms
bonded to
central atom
# lone
pairs on
central atom
Arrangement of
electron pairs
Molecular
Geometry
VSEPR
10.1
AB6 6 0 octahedraloctahedral
AB5E 5 1 octahedralsquare
pyramidalAB4E2 4 2 octahedral
square
planar
Xe
F F
FF
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10.1
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Predicting Molecular Geometry
1. Draw Lewis structure for molecule.
2. Count number of lone pairs on the central atom and
number of atoms bonded to the central atom.
3. Use VSEPR to predict the geometry of the molecule.
What are the molecular geometries of SO2 and SF4?
(In SF4, S uses an expanded octet of 10.)
AB2E bent
S
F
F
F F
AB4E
See-Saw
(distorted
Tetrahedron)
10.1
S
OO
SO
O
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Dipole Moments and Polar Molecules
10.2
H F
electron rich
regionelectron poor
region
+
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10.2
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10.2
Which of the following molecules have a dipole moment?
H2O, CO2, SO2, and CH4
OH
H
dipole moment
polar molecule
SO
O
CO O
no dipole moment
nonpolar molecule
dipole moment
polar molecule
C
H
H
HH
no dipole moment
nonpolar molecule
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10.2
Chemistry In Action: Microwave Ovens
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Bond Dissociation Energy Bond Length
H2
F2
436.4 kJ/mole
150.6 kJ/mole
74 pm
142 pm
Valence bond theory bonds are formed by sharingof e- from overlapping atomic orbitals.
Overlap Of
2 1s
2 2p
How does Lewis theory explain the bonds in H2 and F2?
Sharing of two electrons between the two atoms.
10.3
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Hybridization mixing of two or more atomic
orbitals to form a new set of hybrid orbitals.
1. Mix at least 2 nonequivalent atomic orbitals (e.g. sand p). Hybrid orbitals have very different shape
from original atomic orbitals.
2. Number of hybrid orbitals is equal to number ofpure atomic orbitals used in the hybridization
process.
3. Covalent bonds are formed by:
a. Overlap of hybrid orbitals with atomic orbitals
b. Overlap of hybrid orbitals with other hybrid
orbitals 10.4
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10.4
F ti f 2 H b id O bit l
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Formation ofsp2 Hybrid Orbitals
10.4
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Formation ofsp Hybrid Orbitals
10.4
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# of Lone Pairs
+
# of Bonded Atoms Hybridization Examples
2
3
4
5
6
sp
sp2
sp3
sp3d
sp3d2
BeCl2
BF3
CH4, NH3, H2O
PCl5
SF6
How 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
10.4
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10.4
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Sigma ( ) and Pi Bonds ( )
Single bond1 sigma bond
Double bond 1 sigma bond and 1 pi bond
Triple bond 1 sigma bond and 2 pi bonds
How many and bonds are in the acetic acid
(vinegar) molecule CH3COOH?
C
H
H
CH
O
O H bonds = 6+ 1 = 7
bonds = 1
10.5
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Sigma bond (
) electron density between the 2 atoms
Pi bond ( ) electron density above and below plane of nuclei
of the bonding atoms 10.5
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10.5
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10.5
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Molecular orbital theory bonds are formed frominteraction of atomic orbitals to form molecular
orbitals.
OO
No unpaired e-
Should be diamagnetic
Experiments show O2 is paramagnetic
(has UNPAIRED e-)
10.6
MO Theory is NOT in the
AP Chemistry Curriculumand will NOT be on the
AP exam! This is just a
quick overview!
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Energy levels of bonding and antibonding molecular
orbitals in hydrogen (H2).
A bonding molecular orbitalhas lower energy and greaterstability than the atomic orbitals from which it was formed.
An antibonding molecular orbitalhas higher energy and
lower stability than the atomic orbitals from which it was
formed. 10.6
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10.6
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1. The number of molecular orbitals (MOs) formed is always
equal to the number of atomic orbitals combined.
2. The more stable the bonding MO, the less stable the
corresponding antibonding MO.
3. The filling of MOs proceeds from low to high energies.
4. Each MO can accommodate up to two electrons.
5. Use Hunds rule when adding electrons to MOs of the
same energy.
6. The number of electrons in the MOs is equal to the sum of
all the electrons on the bonding atoms.
10.7
Molecular Orbital (MO) Configurations
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bond order=1
2
Number of
electrons in
bonding
MOs
Number of
electrons in
antibonding
MOs
(-
)
10.7
bond
order
1 0
Delocalized molecular orbitals are not confined between
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Delocalized molecular orbitals are not confined between
two adjacent bonding atoms, but actually extend over three
or more atoms.
10.8
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