ap ch 10 bonding ii

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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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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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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


AB5 5 0trigonal

bipyramidal

trigonal

bipyramidal


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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

AB3 3 0trigonal

planar

trigonal

planar

10.1


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


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


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


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


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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ap ch 10 bonding ii

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