Chapter 10 bonding theory and molecular structure
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Chapter 10 Bonding Theory and Molecular Structure. Molecular Shapes The VSEPR model electron-pair geometries molecular geometries Molecular polarity Valence Bond Theory Covalent bonding and orbital overlap Hybrid orbitals sp hybrid orbitals sp 2 hybrid orbitals sp 3 hybrid orbitals

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Chapter 10 Bonding Theory and Molecular Structure

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Chapter 10 bonding theory and molecular structure

Chapter 10Bonding Theory and Molecular Structure


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • The VSEPR model

      • electron-pair geometries

      • molecular geometries

    • Molecular polarity

  • Valence Bond Theory

    • Covalent bonding and orbital overlap

    • Hybrid orbitals

      • sp hybrid orbitals

      • sp2 hybrid orbitals

      • sp3 hybrid orbitals

      • hybridization involving d orbitals

    • Multiple bonds

      • double bonds

      • triple bonds

  • Molecular Orbital Theory

    • First-row diatomics

    • Second-row diatomics

  • Benzene and Aromatic Compounds


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • The VSEPR model

      • electron-pair geometries

Valence Shell Electron Pair Repulsion Theory: regions of electron density

(single, double, or triple bonds or lone pairs) arrange themselves around an

atom to be as far apart as possible (electron pair repulsion).

Electron pair geometries:


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • The VSEPR model

      • molecular geometries


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • The VSEPR model

      • molecular geometries

Electron pair geometry: tetrahedral

Molecular geometry:

tetrahedral

trigonal pyramidal

bent


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • The VSEPR model

      • molecular geometries

NI3SO2

PCl4–NO3–

OF2SO32–

BrCl3PO43–


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • Molecular polarity

Molecular polarity  physical and chemical properties

d+d–

bonds:if DX > 0  polar bondA—B

molecules and ions: if dipoles do not exactly cancel, molecule will be polar

BeCl2BF3CH2O

CCl4CHCl3NH3

dipole


Chapter 10 bonding theory and molecular structure

  • Molecular Shapes

    • Molecular polarity

PCl3F2

CO32–

CHO2–


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Covalent bonding and orbital overlap

Bonds are formed using valence electrons and orbitals:

overlap

atomic orbitalsmolecular orbitals (covalent bonds)

e.g.,


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Covalent bonding and orbital overlap

But what about CH4?

Tetrahedral, all bonds

equivalent. How do we

get this from s and p a.o.s?


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

      • sp hybrid orbitals

BeH2 facts:

2 equivalent bonds


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

      • sp2 hybrid orbitals

BH3 facts:

trigonal planar,

3 equivalent bonds


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

      • sp3 hybrid orbitals

tetrahedral,

4 equivalent bonds

CH4 facts:


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

      • sp3 hybrid orbitals


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

      • hybridization involving d orbitals


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

Summary:

e– pair geometryhybridization

linearsp

trigonal planarsp2

tetrahedralsp3

trigonal bipyramidalsp3d

octahedralsp3d2


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Hybrid orbitals

What is the hybridization of the central atom in each of the following?

CCl4BrCl3

BF3SF6

NH3BeCl2

PCl4–XeF4


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Multiple bonds

      • double bonds

trigonal planar = sp2

all six atoms lie

in same plane

C2H4 facts:


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

    • Multiple bonds

      • triple bonds

C2H2 facts:

linear = sp


Chapter 10 bonding theory and molecular structure

  • Valence Bond Theory

What is the hybridization of each indicated atom in the following

molecule? How many sigma and pi bonds are in the molecule?


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

Fact: O2 is paramagnetic!

Lewis structure

VSEPR

Valence bond theory

  • sp2 hybridized

  • lone pairs in sp2 hybrid orbitals

  • bonding pairs in s and p bonds

All show

all electrons

paired.


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

Overlap of wave functions:

constructive

overlap

destructive

overlap


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • First-row diatomics

Overlap of 1s orbitals:

s*1s

antibonding m.o.

(higher energy than

separate atoms)

s1s

bonding m.o.

(lower energy than

separate atoms)


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • First-row diatomics

(no. of e– in bonding m.o.s) - (no. of e– in antibonding m.o.s)

2

bond order =

H2

b.o. = 1 (i.e., lower energy than separate atoms)


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • First-row diatomics

He2

He2+

b.o. = 0

b.o. = 0.5


Chapter 10 bonding theory and molecular structure

z

z

x

x

y

y

  • Molecular Orbital Theory

    • Second-row diatomics

Overlap of 2s and 2p orbitals

2s s2s and s*2s

(same as 1s),

then 2p orbitals give:

(i.e., 8 a.o.s  8 m.o.s)


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • Second-row diatomics

E


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • Second-row diatomics


Chapter 10 bonding theory and molecular structure

  • Molecular Orbital Theory

    • Second-row diatomics


Chapter 10 bonding theory and molecular structure

benzene

C6H6

6 e– in a cyclic,

planar p system

 aromatic stabilization

all sp2

120º

  • Benzene and Aromatic Compounds

planar

hexagon


Chapter 10 bonding theory and molecular structure

naphthalene

benzo[a]pyrene

(carcinogen)

p-dichlorobenzene

  • Benzene and Aromatic Compounds

methylbenzene

toluene

1,2-dimethylbenzene

ortho-dimethylbenzene

(o-xylene)

(meta-xylene)

(para-xylene)


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