9.4. Intermolecular Forces http://www.ck12.org
9.4 Intermolecular Forces
Lesson Objectives
- Define and give examples of intermolecular forces.
- Explain what it means for a molecule to be polar.
- Describe various types of intermolecular interactions, including ion-ion, ion-dipole, dipole-dipole, and disper-
sion forces.
Lesson Vocabulary
- dipole: Occurs when two opposite charges are separated by some distance.
- molecular dipole: The overall dipole in a molecule, or the geometric sum of all the individual bond dipoles
in a molecule. - dipole-dipole force: The force of two polar molecules interacting with one another.
- dispersion force: An attractive force that arises as a result of temporary dipoles induced in atoms or molecules.
- hydrogen bond: A bond that only occurs in molecules where hydrogen is covalently bonded to one of three
elements: fluorine, oxygen, or nitrogen.
Check Your Understanding
Recalling Prior Knowledge
- What is electronegativity?
- How does electronegativity influence the charge distribution within a molecule?
Introduction
In some ways, a collection of gas molecules represents the simplest form of matter. Because the individual molecules
are so far apart, they have only fleeting interactions with one another. In contrast, molecules that have clustered
together to form a liquid or solid are constantly exerting forces on each other. In fact, it is only because of these
attractive forces that molecular solids and liquids exist at all. In this lesson, we will look at some of the ways in
which molecules and ions attract one another to form solids and liquids.