1. Intramolecular Forces vs Intermolecular Forces

2. Intramolecular Forces
There are 2 types of attraction in molecules:
intramolecular bonds & intermolecular forces
We have already looked at intramolecular bonds
These are forces that hold atoms together to form molecules
Examples: Ionic, Non-Polar Covalent, and Polar Covalent

4. Intermolecular Forces
Intermolecular forces (IMF) have to do with the attraction between molecules
There are 3 different levels of strength in IMFs
Hydrogen bonding (the strongest)
Dipole-dipole Forces
London Dispersion Forces (the weakest)
POLAR
NON-POLAR

5. H-bonds & Dipole-Dipole
Remember: POLAR BEARS DON’T SHARE FAIR
The unequal sharing in polar bonds cause a slight (+) charge on one atom, and a slight (-) charge on the other atom
Dipole-Dipole

6. So what’s a H-bond? It occurs when N, O, or F are bonded to H
H-bonding is a special type of dipole - dipole attraction that is very strong
It occurs when N, O, or F are bonded to H
Bonding Is
FHON!

7. Hydrogen bonds What do you need?
A hydrogen atom covalently bonded to an electronegative atom … N, O or F.
A lone pair of electrons on the electronegative atom.
If only one of these conditions is met, you don’t get H-bonds

8. Polar Covalent bond

9. London Dispersion Forces
aka “van der Waal” forces
Seen in non-polar molecules
Happen because partial charges can show up for just an instant (b/c e-s are moving)
This creates a temporary dipole
When e- leaves, the dipole is gone

11. REMEMBER All bonds are stronger than all intermolecular forces.
Molecules that use bonding only will have the strongest structures
Molecules that use bonding and intermolecular forces will have weaker structures, where the strength depends upon the type of intermolecular force used
Molecules that use intermolecular forces and no bonding will have the weakest structures known; examples of these would be Noble Gases.

12. REFLECTION: On the LEFT side of your notes:
List the different types of bonds
STRONGEST on top
WEAKEST on bottom