Van der Waals forces

Definition

Van der Waals forces are weak intermolecular forces that arise from the interactions between induced or permanent dipoles in molecules. They play a crucial role in determining the physical properties of liquids and solids.

5 Must Know Facts For Your Next Test

1. Van der Waals forces include London dispersion forces, dipole-dipole interactions, and hydrogen bonds.
2. These forces are weaker than covalent and ionic bonds but essential for phenomena such as boiling points and melting points.
3. London dispersion forces occur due to temporary fluctuations in electron distribution even in nonpolar molecules.
4. Dipole-dipole interactions occur between molecules with permanent dipoles, aligning positive and negative ends.
5. Hydrogen bonds, a special type of dipole-dipole interaction, occur when hydrogen is bonded to highly electronegative atoms like N, O, or F.

Review Questions

• What are the three types of van der Waals forces?
• How do London dispersion forces differ from dipole-dipole interactions?
• Why are van der Waals forces important for understanding boiling points?

Related terms

London Dispersion Forces:

Weak intermolecular forces arising from temporary fluctuations in electron distribution within atoms or molecules.

Dipole-Dipole Interactions:

Forces occurring between two polar molecules due to the attraction between their positive and negative ends.

Hydrogen Bonding:

A strong type of dipole-dipole interaction occurring when hydrogen is bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine.