Van der Waals Forces (between molecules)

1. Dipole-Dipole Forces (between polar molecules)

 (see board)

2. London Forces

 (see board)

3. Hydrogen Bonds (between molecules)

Very strong dipole-dipole force which occurs when H is bonded to N, O, or F (small & electroneg.)

 (see board)

Relative Strength of Forces

Force	Energy, kJ	Strength
Covalent bonding	100 - 1000	Strong
Ionic bonding	100 - 1000	Strong
Metallic bonding	100 - 1000	Strong
Hydrogen bonding	10 - 40	Moderate
Van der Waals	0.1 - 10	Weak

Examples

NaCl

C₂H₄ (ethylene)

(CH₂CH₂)_n (polyethylene)

W

C(diamond)

B

C₁₂H₂₂O₁₁ (sucrose)