Advanced Placement (AP) Chemistry Practice Exam

What are London dispersion forces primarily associated with?

1. Temporary dipoles in all molecules

2. Hydrogen bonding between polar molecules

3. Ionic interactions between charged molecules

4. Covalent bonding in molecular compounds

The correct answer is: Temporary dipoles in all molecules

London dispersion forces are primarily associated with temporary dipoles that occur in all molecules, regardless of whether they are polar or nonpolar. These forces arise due to the movement of electrons within atoms, which can create temporary shifts in electron density. As electrons move, they can induce a dipole by causing slight positive and negative charges to form within an atom or molecule, leading to a momentary imbalance. When these temporary dipoles influence neighboring atoms or molecules, attractive interactions can occur, leading to what is termed London dispersion forces. These forces are significant, especially in larger atoms or molecules with more electrons, as they are more likely to have larger fluctuations in electron distribution. Thus, while London dispersion forces can be weak, they play a crucial role in the physical properties of substances, especially gases and nonpolar compounds. Other options present interactions that either don't specifically pertain to London dispersion forces or describe entirely different types of forces. Hydrogen bonding is a specific strong type of dipole-dipole interaction that occurs between polar molecules and is not related to the temporary dipoles formed by London dispersion forces. Ionic interactions involve the electrostatic attraction between charged particles and do not pertain to temporary dipoles or the nature of London dispersion forces. Covalent bonding concerns the sharing