Chapter 10: Bonding and Structure - Theories

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Chapter 10 Bonding and Structure - Theories
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• 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
• Delocalized p bonding
• Molecular Orbital Theory
• First-row diatomics
• the hydrogen molecule
• bond order
• other species
• Second-row diatomics
• molecular orbitals from 2s and 2p atomic orbitals
• electronic configurations and molecular
  properties

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• Valence Bond Theory
• Covalent bonding and orbital overlap

Bonds are formed using valence electrons and
orbitals
overlap
atomic orbitals molecular orbitals (covalent
bonds)
e.g.,
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• 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?
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• Valence Bond Theory
• Hybrid orbitals
• sp hybrid orbitals

BeH2 facts
2 equivalent bonds
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• Valence Bond Theory
• Hybrid orbitals
• sp2 hybrid orbitals

BH3 facts
trigonal planar, 3 equivalent bonds
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• Valence Bond Theory
• Hybrid orbitals
• sp3 hybrid orbitals

tetrahedral, 4 equivalent bonds
CH4 facts
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• Valence Bond Theory
• Hybrid orbitals
• sp3 hybrid orbitals

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• Valence Bond Theory
• Hybrid orbitals
• hybridization involving d orbitals

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• Valence Bond Theory
• Hybrid orbitals

Summary e pair geometry hybridization linear
sp trigonal planar sp2 tetrahedral sp3 trigon
al bipyramidal sp3d octahedral sp3d2
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• Valence Bond Theory
• Hybrid orbitals

What is the hybridization of the central atom in
each of the following? CCl4 BrCl3 BF3 SF6
NH3 BeCl2 PCl4 XeF4
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• Valence Bond Theory
• Multiple bonds
• double bonds

trigonal planar sp2
all six atoms lie in same plane
C2H4 facts
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• Valence Bond Theory
• Multiple bonds
• triple bonds

C2H2 facts
linear sp
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• Valence Bond Theory

e.g., What is the hybridization of each indicated
atom in the following molecule? How many sigma
and pi bonds are in the molecule?
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• Valence Bond Theory
• Delocalized p bonding

all sp2, trigonal planar (120º, planar hexagon)
benzene, C6H6
6 e in 6 p orbitals
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• Valence Bond Theory
• Delocalized p bonding

4 electrons in 3 p orbitals
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• Molecular Orbital Theory

• 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.
But O2 is paramagnetic! How do we explain this?
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• Molecular Orbital Theory

Overlap of wave functions
constructive overlap
destructive overlap
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• Molecular Orbital Theory
• First-row diatomics
• the hydrogen molecule

s1s antibonding m.o. (higher energy
than separate atoms)
s1s bonding m.o. (lower energy than separate
atoms)
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• Molecular Orbital Theory
• First-row diatomics
• bond order

(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)
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• Molecular Orbital Theory
• First-row diatomics
• other species

He2
He2
b.o. 0
b.o. 0.5
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• Molecular Orbital Theory
• Second-row diatomics
• molecular orbitals from 2s and 2p atomic orbitals

2s ? s2s and s2s (same as 1s), then 2p orbitals
give (i.e., 8 a.o.s ? 8 m.o.s)
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• Molecular Orbital Theory
• Second-row diatomics
• molecular orbitals from 2s and 2p atomic orbitals

E
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• Molecular Orbital Theory
• Second-row diatomics
• electron configurations and molecular properties

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• Molecular Orbital Theory
• Second-row diatomics
• heteronuclear diatomic molecules