Intermolecular Forces (Ch6) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Intramolecular vs. Intermolecular Hold atoms together within a molecule (chem. Bonding: ionic and covalent) Intermolecular Attractive forces between molecules Responsible for many properties of matter (ex. MP and BP)

3 Types of Intermolecular Forces 1. Van der Waals Forces – increase with increasing mass Dipole-Dipole Forces (attraction) Attractive forces between polar molecules The larger the dipole, the greater the force of attraction

London Disperson Forces (dipole-induced dipole force) Strength depends of polarizability, which increases as molecular mass increases (can be stronger than dipole-dipole) Strength of LDF increases as number of electrons increases; this is proportional to the mass; therefore, as mass increases, so does LDF

3 Types of Intermolecular Forces 2. Ion-Dipole Forces Attraction between an ion and a polar molecule As charge increases the ability to attract polar molecules increases

3 Types of Intermolecular Forces 3. Hydrogen Bonding Limited to compounds containing H bonded to N, O, or F Bond occurs between the H of one molecule and the N, O or F of another molecule Strongest intermolecular force (compare boiling pt of water to other similar compounds) Is a very strong dipole-dipole force

Why is an H bond so unusually strong? The great polarity of the bond The close approach of dipoles allowed by the small size of the hydrogen atom

Network Solid/Covalent Solid