1. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
When bonding occurs, atomic orbitals overlap to produce molecular orbitals.
Below is an example of “s” orbitals overlapping forming a sigma-bonding molecular orbital.
H H
A sigma bond is the result of a molecular orbital that is symmetrical around the axis connecting the atomic nuclei.

2. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
Another example of a sigma bond: F F

3. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
An oxygen molecule has two types of bonds, sigma and pi.
Pi bonds are not symmetrical around the bonding axis.

4. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
A nitrogen molecule has one sigma and two pi bonds.

5. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
“VSEPR” stands for Valence Shell Electron Pair Repulsion Theory. In general, this theory states that electrons within molecules repel each other. The amount of repulsion is dependent upon whether or not the electrons are in bonds.
* Electron pairs will position themselves as far from other electron pairs as possible*
Levels of Repulsion
Example: H2O
Strongest: Un-shared:Un-shared Repulsion
Stronger: Un-shared : Shared Repulsion
Strong: Shared : Shared Repulsion O H H

6. O H H O C O 1800 104.50 Test Your Knowledge
Why is H2O a bent molecule while CO2 is a linear molecule? O O C O H H
1800
104.50
Bond Angle
Bond Angle
Water has more forces of repulsion acting on the bonded
Answer:_______________________________________________________________________________
electrons than does carbon dioxide.

7. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
The pictures below show why water and carbon dioxide are shaped differently, even though each molecule contains 3 atoms.

8. N F H H B H F F 1200 107.30 Test Your Knowledge
Which molecule will exhibit the larger bond angles, and why? N F
1200 H H B H F F
107.30
BF3 has the larger bond angles because it has the least
Answer:_______________________________________________
______________________________________________________
amount of electron pair repulsion (No unshared-pair repulsion).

9. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
*Electron pairs always seek the furthest distance from each other!!

10. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
Molecular Shapes

11. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
Hybrid orbitals are orbitals of equal energy produced by the combination of two or more orbitals on the same atom.
For Example: Carbon
Hybridization
4 hybrid orbitals 1s 2s 2p 1s
2sp3
When the “s” orbital combines with 3 “p” orbitals, it is called sp3 hybridization.
*Hybridization helps explain the bonding and geometry of many molecules .

12. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
Hybridization 2s 2p
2sp3

13. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
sp3 Hybridization
* Hybridization is another way of understanding why molecules take on the shapes that they do.
*Central atoms that have 4 areas of electron density within a molecule will exhibit sp3 hybridization.

14. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories

15. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
When the “s” orbital combines with 2 “p” orbitals, it is called sp2 hybridization.

16. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
*Central atoms that have 3 areas of electron density within a molecule will exhibit sp2 hybridization.

17. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
(C2H4)
Ethene and "sp2" Hybridization
Sigma Bond
Sigma Bond
Sigma Bond
Sigma Bond
Sigma Bond

18. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
A pi bond occurs when the overlapping orbitals do not lie directly on the bond axis, as seen in the picture below.
Pi bonds only occur in double and triple covalent bonds.
Double bond: 1 sigma & 1 pi bond
Triple bond: 1 sigma & 2 pi bonds

19. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
*When the “s” orbital combines with 1 “p” orbital, it is called sp hybridization.

20. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
*Central atoms that have 2 areas of electron density within a molecule will exhibit sp hybridization.
sp Hybridization

21. Chapters 8 , 9 & 22: Covalent Bonding and Naming Compounds
Sec. 8.3: Bonding Theories
Pi bonds in Ethyne
(C2H2)
Each Carbon Atom has 2 areas of electron density.
sp hybridization H C C H
How many pi bonds are in ethyne? ___________
Two