2.2.8 Intermolecular Forces
Van der Waals forces and Hydrogen Bonding.
Instantaneous Dipole → Induced Dipole
Electrons wobble randomly. For a split second, one side is δ-.
Strength depends on: 1) Number of electrons (Polarizability) 2) Surface Area.
1. London (Dispersion) ForcesWeakest
Temporary instantaneous dipoles induce dipoles in neighbors. Present in ALL molecules.
Strength increases with molar mass (more electrons = higher polarizability).
2. Dipole-Dipole ForcesMedium
Attraction between permanent dipoles in polar molecules.
3. Hydrogen BondingStrongest
Occurs when H is bonded directly to N, O, or F.
Creates a very strong dipole interactions. Responsible for water's high boiling point.