1. Chapter 11: Chemical Bonding II: Additional Aspects
Chemistry 140 Fall 2002
CHEMISTRY
Ninth
Edition
GENERAL
Principles and Modern Applications
Petrucci • Harwood • Herring • Madura
Chapter 11: Chemical Bonding II: Additional Aspects
Philip Dutton
University of Windsor, Canada
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General Chemistry: Chapter 11
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2. Contents 11-1 What a Bonding Theory Should Do
Chemistry 140 Fall 2002
Contents
11-1 What a Bonding Theory Should Do
11-2 Introduction to the Valence-Bond Method
11-3 Hybridization of Atomic Orbitals
11-4 Multiple Covalent Bonds
11-5 Molecular Orbital Theory
11-6 Delocalized Electrons: Bonding in the Benzene Molecule
11-7 Bonding in Metals
11-8 Some Unresolved Issues: Can Electron Charge-Density Plots Help?
Focus On Photoelectron Spectroscopy
General Chemistry: Chapter 11
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3. 11-1 What a Bonding Theory Should Do
Bring atoms together from a distance.
e- are attracted to both nuclei.
e- are repelled by each other.
Nuclei are repelled by each other.
Plot the total potential energy verses distance.
-ve energies correspond to net attractive forces.
+ve energies correspond to net repulsive forces.
General Chemistry: Chapter 11
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4. Potential Energy Diagram
General Chemistry: Chapter 11
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5. 11-2 Introduction to the Valence-Bond Method
Atomic orbital overlap describes covalent bonding.
Area of overlap of orbitals is in phase.
A localized model of bonding.
General Chemistry: Chapter 11
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6. General Chemistry: Chapter 11
Chemistry 140 Fall 2002
Bonding in H2S
General Chemistry: Chapter 11
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7. General Chemistry: Chapter 11
EXAMPLE 11-1
Using the Valence-Bond Method to Describe a Molecular Structure.
Describe the phosphine molecule, PH3, by the valence-bond method..
Identify valence electrons:
General Chemistry: Chapter 11
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8. General Chemistry: Chapter 11
Chemistry 140 Fall 2002
EXAMPLE 11-1
Sketch the orbitals: H
Overlap the orbitals: H H H
Describe the shape:
Trigonal pyramidal
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9. 11-3 Hybridization of Atomic Orbitals
General Chemistry: Chapter 11
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10. General Chemistry: Chapter 11
sp3 Hybridization
General Chemistry: Chapter 11
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11. General Chemistry: Chapter 11
sp3 Hybridization
General Chemistry: Chapter 11
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12. General Chemistry: Chapter 11
Bonding in Methane
General Chemistry: Chapter 11
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13. sp3 Hybridization in Nitrogen
General Chemistry: Chapter 11
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14. General Chemistry: Chapter 11
Bonding in Nitrogen
General Chemistry: Chapter 11
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15. General Chemistry: Chapter 11
sp2 Hybridization
General Chemistry: Chapter 11
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16. General Chemistry: Chapter 11
Orbitals in Boron
General Chemistry: Chapter 11
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17. General Chemistry: Chapter 11
sp Hybridization
General Chemistry: Chapter 11
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18. General Chemistry: Chapter 11
Orbitals in Beryllium
General Chemistry: Chapter 11
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19. sp3d and sp3d2 Hybridization
General Chemistry: Chapter 11
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20. Hybrid Orbitals and VSEPR
Write a plausible Lewis structure.
Use VSEPR to predict electron geometry.
Select the appropriate hybridization.
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21. 11-4 Multiple Covalent Bonds
Ethylene has a double bond in its Lewis structure.
VSEPR says trigonal planar at carbon.
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22. General Chemistry: Chapter 11
Ethylene
General Chemistry: Chapter 11
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23. General Chemistry: Chapter 11
Acetylene
Acetylene, C2H2, has a triple bond.
VSEPR says linear at carbon.
General Chemistry: Chapter 11
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24. 11-5 Molecular Orbital Theory
Atomic orbitals are isolated on atoms.
Molecular orbitals span two or more atoms.
LCAO
Linear combination of atomic orbitals.
Ψ1 = φ1 + φ Ψ2 = φ1 - φ2
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25. Combining Atomic Orbitals
Chemistry 140 Fall 2002
Combining Atomic Orbitals
General Chemistry: Chapter 11
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26. Molecular Orbitals of Hydrogen
General Chemistry: Chapter 11
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27. Basic Ideas Concerning MOs
Chemistry 140 Fall 2002
Basic Ideas Concerning MOs
Number of MOs = Number of AOs.
Bonding and antibonding MOs formed from AOs.
e- fill the lowest energy MO first.
Pauli exclusion principle is followed.
Hund’s rule is followed
General Chemistry: Chapter 11
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28. General Chemistry: Chapter 11
Bond Order
Stable species have more electrons in bonding orbitals than antibonding.
Bond Order =
No. e- in bonding MOs - No. e- in antibonding MOs 2
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29. Diatomic Molecules of the First-Period
BO = (e-bond - e-antibond )/2
BO = (1-0)/2 = ½
H2+
BO = (2-0)/2 = 1 H2
BO = (2-1)/2 = ½
He2+
BO = (2-2)/2 = 0
He2
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30. Molecular Orbitals of the Second Period
First period use only 1s orbitals.
Second period have 2s and 2p orbitals available.
p orbital overlap:
End-on overlap is best – sigma bond (σ).
Side-on overlap is good – pi bond (π).
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31. Molecular Orbitals of the Second Period
General Chemistry: Chapter 11
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32. General Chemistry: Chapter 11
Combining p orbitals
General Chemistry: Chapter 11
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33. Expected MO Diagram of C2
Slide 33 of General Chemistry: Chapter Prentice-Hall © 2007
General Chemistry: Chapter 11
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34. Modified MO Diagram of C2
General Chemistry: Chapter 11
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35. MO Diagrams of 2nd Period Diatomics
Slide 35 of General Chemistry: Chapter Prentice-Hall © 2007
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General Chemistry: Chapter 11
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36. MO Diagrams of Heteronuclear Diatomics
General Chemistry: Chapter 11
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37. 11-6 Delocalized Electrons
General Chemistry: Chapter 11
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38. General Chemistry: Chapter 11
Benzene
General Chemistry: Chapter 11
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39. General Chemistry: Chapter 11
Benzene
General Chemistry: Chapter 11
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40. General Chemistry: Chapter 11
Benzene
General Chemistry: Chapter 11
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41. General Chemistry: Chapter 11
Ozone
General Chemistry: Chapter 11
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42. General Chemistry: Chapter 11
11-7 Bonding in Metals
Electron sea model
Nuclei in a sea of e-.
Metallic luster.
Malleability.
Force applied
General Chemistry: Chapter 11
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43. General Chemistry: Chapter 11
Bonding in Metals
Band theory.
Extension of MO theory.
N atoms give N orbitals that are closely spaced in energy.
N/2 are filled.
The valence band.
N/2 are empty.
The conduction band.
General Chemistry: Chapter 11
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44. General Chemistry: Chapter 11
Band Theory
General Chemistry: Chapter 11
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45. General Chemistry: Chapter 11
Chemistry 140 Fall 2002
Semiconductors
General Chemistry: Chapter 11
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46. General Chemistry: Chapter 11
Photovoltaic Cells
General Chemistry: Chapter 11
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47. 11-8 Some Unresolved Issues: Can Electron Charge-Density Plots Help?
Accommodation of extra valence electrons?
In molecules such as SF6 and SF4.
Are d-orbitals used in the bonding description?
What provides the more fundamental view of molecular shape?
VSEPR?
Hybridization?
General Chemistry: Chapter 11
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48. General Chemistry: Chapter 11
Bonding in SF6 ?
0.53-
3.17+ ?
General Chemistry: Chapter 11
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49. Isodensity Contour Map of SCl2
General Chemistry: Chapter 11
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50. Contour Map of the Electron Density in SCl2
General Chemistry: Chapter 11
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51. General Chemistry: Chapter 11
Bonding in H2SO4 and SO42-
0.002 au
0.22 au
0.28 au
General Chemistry: Chapter 11
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52. Focus on Photoelectron Spectroscopy
General Chemistry: Chapter 11
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53. End of Chapter Questions
Set up a strategy for your problem.
This is your road map.
In a time of stress (i.e. an exam) your strategy will keep you on the path of the problem.
Change your strategy
If it is identifiably faulty (remember your units).
General Chemistry: Chapter 11
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