1. Unit 4
Bonding Theories

2. O = O O = O VSEPR Theory Valence Shell Electron Pair Repulsion
Predicts the shapes of covalent molecules
The repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible.
O = O
O = O

3. VSEPR Theory
In your notes, create a chart to help you learn the various shapes, bond angles, etc.
SHAPE
# BONDS
# LONE PAIRS
BOND ANGLE
EXAMPLE
PICTURE
HYBRIDIZATION

4. - - Molecular Shapes 180o 120o 104.5o 109.5o 107o SHAPE DESCRIPTION
ILLUSTRATION
Linear
Bond Angle = 180o
One or two bonding pairs, no lone pairs X A
180o X A
104.5o
Bent
Bond Angle = 104.5o
Two bonding pairs, two lone pairs X A
107o X A
120o
Trigonal Planar
Bond Angle = 120o
3 bonding pairs, no lone pairs X A
109.5o
Trigonal Pyramidal
Bond Angle = 107o
3 bonding pairs, one lone pair
Tetrahedral
Bond Angle = 109.5o
Four bonding pairs, no lone pairs

5. Lone Pairs
Take up MORE space
SQUEEZE the bond angle X A X A

6. HF CH4 Practice: Determine the shape of each molecule: LINEAR
TETRAHEDRAL

7. More Practice: BF3 NH3 SeCl2 TRIGONAL PLANAR TRIGONAL PYRAMIDAL BENT F

8. Molecular Shapes cont.
The shapes we have looked at all had at most 4 bonding sites.
However, there are MANY compounds that have MORE than 4 bonding sites. Therefore, there is the possibility for many more types of geometry.

9. Molecular Shapes cont. Shape Atoms on Lone Pairs Example central atom
Trigonal PCl5
Bipyramidal
Bond angle: 90o and 120o
See Saw SF4
Bond angle: 180o and 120o

10. Molecular Shapes cont. Shape Atoms on Lone Pairs Example central atom
T-shaped BrF3
Bond angle: 90o
Linear
Bond angle: 180o I3

11. Molecular Shapes cont. Octahedral 6 0 SF6 Bond angle: 90o
Shape Atoms on Lone Pairs Example
central atom
Octahedral SF6
Bond angle: 90o
Square Pyramidal BrF5
Bond Angle: 90o

12. Molecular Shapes cont. Shape Atoms on Lone Pairs Example central atom
Square Planar XeF4
Bond Angle: 90o

13. Hybrid Orbitals Review – what is the electron configuration of Carbon?
1s2 2s2 2p The orbital notation is: ____ ____ ____ ____ ____
There are only 2 places for other atoms to bond…..but we know carbon can bond with 4 things.
So, Carbon will hybridize or move its electrons around to make more available spots for bonding.

14. Hybrid Orbitals Ex. Carbon 2p ___ ___ ___ sp3 ___ ___ ___ ___ 2s ____
Now carbon has 4 available bonding sites, and all are of equal energy.

15. Hybridization
There are 4 possible locations for bonding, or 4 charge clouds.
sp3 hybridization can lead to the following types of geometry:
Tetrahedral
Trigonal Pyramidal
Bent
Ex. 1 CH4

16. Hybrid Orbitals example
sp3 hybridization
Ex 2. NH3

17. Hybrid Orbital Example
Ex 3. Water – H20
Draw the Hybrid orbitals

18. Hybrid Orbitals sp2 Hybridization
What is the electron configuration for Boron?
1s2 2s2 2p1
How many bonding sites does Boron have?
So….the orbitals need to hybridize to reflect the correct number of bonding sites
(or charge clouds).

19. Hybrid Orbitals
Ex. BF3 – notice that only 2 of the p orbitals hybridize, the 3rd p orbital remains unchanged (and at the higher energy.)

20. Hybrid Orbitals sp Hybridization
Can you determine what orbitals will be hybridized?
How many charge clouds will there be?
Note that the energy is now HIGHER than the s orbital, but LOWER than the p orbital.

21. Hybrid Orbitals
There is currently a debate among scientists as to whether d orbitals hybridize or not.
For the AP exam, hybridization of d orbitals is NOT required info.
However, it IS important to know how potential d hybridization correlates to molecular geometry.
Therefore, we will look at the number of charge clouds (bonds to central atom + lone pairs) and compare that to molecular shapes.

22. Sigma and Pi bonds
Single bonds can also be referred to as sigma bonds. (σ)
Where the two bonds overlap is the covalent bond – where they are sharing electrons.

23. Sigma and Pi Bonds
When there is a double (or triple) bond, the 2nd (or 3rd) bonds made are pi (π) bonds.
Pi bonds

24. Sigma and Pi bonds
Count ALL the bonds in C2H2

25. Agenda
Check homework
Learn how to hybridize orbitals when double and triple bonds are involved
Go over homework (as needed) and molecular geometry worksheet from yesterday
VSEPR matching in groups

26. Hybridization cont.
The first bond that is made is a single (or sigma) bond.
Sigma bonds are made in hybridized orbitals.
If a Pi bond is made, it will do so in an unhybridized orbital.
Ex. CO2

27. Hybridization cont.
Ex. NO2-