1. Chapter 8: Prediction of Molecular Geometry (VSEPR)
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Chapter 8: Prediction of Molecular Geometry (VSEPR)
Copyright © 2010 Pearson Prentice Hall, Inc.

2. Molecular Shapes: The VSEPR Model
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Molecular Shapes: The VSEPR Model
VSEPR: Valence-Shell Electron-Pair Repulsion model
- Electrons in bonds and in lone pairs can be thought of as “charge clouds” that repel one another and stay as far apart as possible, this causing molecules to assume specific shapes.
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3. Linear molecules: Two Charge Clouds
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Linear molecules: Two Charge Clouds
The CO2 molecule
Geometry- linear
- Central atom (C) binds to two other atoms
The HCN molecule
Geometry- linear
- Central atom (C) binds to two other atoms
Copyright © 2010 Pearson Prentice Hall, Inc.

4. Planar molecules: Three Charge Clouds
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Planar molecules: Three Charge Clouds
The H2CO molecule
Geometry- Trigonal Planar
- Central atom (C) binds to three other atoms
The SO2 molecule
Geometry- Bent
- Central atom (S) binds to two other atoms with one lone pair
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5. Tetrahedral Molecules: Four Charge Clouds
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Tetrahedral Molecules: Four Charge Clouds
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6. Chapter 5: Covalent Bonds and Molecular Structure
Tetrahedral Molecules: Four Charge Clouds
2/17/2019
Copyright © 2010 Pearson Prentice Hall, Inc.

7. Bipyrimidal molecules: Five Charge Clouds
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Bipyrimidal molecules: Five Charge Clouds
Copyright © 2010 Pearson Prentice Hall, Inc.

8. Trigonal Bipyrimidal structure
Structure of PCl5
PCl5 forms a trigonal
bipyrimidal shape

9. Electron pairs within this shape generally occupy the equatorial positions

10. Electron-Dot Structures of Polyatomic Molecules
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Electron-Dot Structures of Polyatomic Molecules
Draw an electron-dot structure for SF4.
Step 1:
6 + 4(7) = 34 valence electrons S F S F
Step 3:
Step 2:
Step 2: The central atom is in row 3 so there can be more than 8 electrons.
Step 4: There are no remaining electrons.
Step 5: The central atom has at least 8 electrons so no multiple bonding. S F
Step 4:
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11. The geometry of sulfur tetraflouride (SF4) is a seesaw

12. Look at the geometry of CLI3

13. The geometry of I3

14. Octahedral molecules: Six Charge Clouds
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Octahedral molecules: Six Charge Clouds
Copyright © 2010 Pearson Prentice Hall, Inc.

15. Electron pairs first occupy the axial positions before the equatorial positions

16. Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Copyright © 2010 Pearson Prentice Hall, Inc.

17. Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Copyright © 2010 Pearson Prentice Hall, Inc.

18. Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
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19. Electronegativity and the periodic table
Chapter 5: Covalent Bonds and Molecular Structure
2/17/2019
Electronegativity and the periodic table
Copyright © 2010 Pearson Prentice Hall, Inc.