1. Draw these shapes Cl2, HCl, H2O, NH3, CH4, BF3 and NH4+, SF6
trigonal planar
tetrahedral
octahedral
pyramidal
non-linear
linear.

2. Dipoles and Van der Waals forces
Describe intermolecular forces based on permanent dipoles, induced dipoles (van der Waals forces), and noble gases.

3. What are intermolecular forces?
What is electronegativity?

4. Permanent Dipole

5. Describing with key words
Molecules with permanent dipoles have intermolecular forces between them. These intermolecular forces are weak electrostatic forces.

6. What molecules have permanent dipoles?
Molecules that have asymmetric bonds usually have dipoles.

7. Van der Waals forces
These are intermolecular forces caused by temporary induced dipoles. Electrons move around randomly, so occasionally there are more one side of a molecule than the other.

8. Two examples
Molecules cause the other molecules to have a temporary dipole. This is called an induced dipole More electrons = stronger Van der Waals
Noble gases
Noble gases are electrically stable, but they can still experience Van der Waals forces.

9. Boiling Points
What do you think these intermolecular attractions mean for boiling points?

10. Plenary
1) What is the different between permanent dipole interactions and Van der Waals forces? 2) Why does xenon have a higher boiling point than helium? 3) Explain why symmetric molecules don’t have dipoles. 4) What type of bonding are dipole-dipole interactions similar to?