Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using...
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![Page 1: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/1.jpg)
Chapter 9Chemical Bonding Theories
Valence Bond Theory: Uses Lewis StructuresBonds form using shared electrons between overlapping orbitals on adjacent atoms.Orbitals arrange around central atom to avoid each other.Two types of bonds: sigma and pi.
Molecular Orbital Theory: Uses MO DiagramsOrbitals on atoms “mix” to make molecular orbtials, which go over 2 or more atoms. Two electrons can be in an orbital.Orbitals are either: bonding, antibonding, or nonbonding.Bonds are either: sigma or pi.
![Page 2: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/2.jpg)
Orbitals on bonding atoms overlap directly between bonding atoms
Sigma () Bonding
Between s orbitals
Between p orbitals
![Page 3: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/3.jpg)
Consider VSEPR Shapes and bonding:
Sigma (s) Bonding
![Page 4: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/4.jpg)
What’s wrong with this picture?
Atoms bond by having their
valence orbitals overlap
![Page 5: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/5.jpg)
Enter question text...
1. 1
2. 2
3. 3
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Orbitals don’t go in same directions as atomic orbitals.
2s
2pz 2px 2py
Orbitals in CH4Orbitals on C
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Orbitals don’t go in same directions as atomic orbitals.
2s
2pz 2px 2py
Orbitals in CH4
Conclusion: Atomic orbitals change shape when they make molecules.
![Page 8: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/8.jpg)
Hybrid Orbitals
Atomic valence orbitals “combine and mix” to form new “Hybrid Orbitals”
Hybrid orbitals go in the VSEPR electron geometry directions.
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Types of Hybrid Orbitals
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Types of Hybrid Orbitals: 2 Pairs
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Types of Hybrid Orbitals: 3 Pairs
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Types of Hybrid Orbitals: 4 Pairs
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![Page 14: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/14.jpg)
Hybrid orbitals in H2O?
1 2 3 4 5
19%
35%
0%4%
42%1. sp
2. sp2
3. sp3
4. sp3d
5. sp3d2
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Hybrid orbitals in O3?
1 2 3 4 5
9%
70%
0%4%
17%
1. sp
2. sp2
3. sp3
4. sp3d
5. sp3d2
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Hybrid orbitals in CO2?
1 2 3 4 5
76%
9%
0%1%
13%
1. sp
2. sp2
3. sp3
4. sp3d
5. sp3d2
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Hybrid orbitals in SF4?
1 2 3 4 5
3% 0%7%
80%
10%
1. sp
2. sp2
3. sp3
4. sp3d
5. sp3d2
![Page 18: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/18.jpg)
Hybrid orbitals used for sigma bonds and lone pairs.
Unhybridized p orbitals used for pi bonds, or they are empty.
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Sigma Bonding
Orbitals overlap directly between two nuclei:
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NH3
![Page 21: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/21.jpg)
CH2O
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Sigma Bonding involves hybrid orbitals and/or H 1s orbitals.
Pi bonding involves unhybridized p orbitals.
Sigma vs. Pi Bonding
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Pi Bond Formation
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Bonding in Ethene
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Bonding in Acetylene
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Bonding in Formaldehyde
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How many bonds in acetonitrile?
1. 7 sigma, 0 pi
2. 6 sigma, 1 pi
3. 5 sigma, 2 pi
4. 4 sigma, 3 pi
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Bonding in Benzene
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Advanced: Allene
Each end carbon is a flat trigonal.
Are they co-planar or perpendicular?
![Page 30: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/30.jpg)
Bonding in Allene
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Conformations vs. Isomers
• Isomers: Molecules with same formula but different structure
• Conformers: Different temporary shapes of the same molecule
![Page 32: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/32.jpg)
Bond Rotations• CAN happen around single bonds
• Cannot happen around double bonds
Examples: dichloroethane and diclhloroethene
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Types of Isomers
• Constitutional: Different bond connections
• Geometric/Stereoisomers: Same connections, different directions
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Cis-Trans Stereoisomerization
When two groups are on a “side” of a molecule.
cis trans
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Can these molecules have cis-trans isomers?
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What are these?
1. Constitutional isomers
2. Stereoisomers
3. Conformations
4. None of these
![Page 37: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/37.jpg)
What are these?
1. Constitutional isomers
2. Stereoisomers
3. Conformations
4. None of these
![Page 38: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/38.jpg)
What are these?
1. Constitutional isomers
2. Stereoisomers
3. Conformations
4. None of these
![Page 39: Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent.](https://reader033.fdocuments.in/reader033/viewer/2022061618/56649d415503460f94a1c2b8/html5/thumbnails/39.jpg)
A message from Mom.