Answer to Question #118451 in Chemistry for Angelina

Question

Which of the following can result in a dispersion force?

When a nonpolar molecule becomes slightly polar for an instant
When the oppositely charged ends of a polar molecule attract each other
When there is a very strong dipole-dipole attraction between a hydrogen atom and a polar-molecule
When an ion comes close enough to a nonpolar molecule to change its electron density

Answer 1

When a nonpolar molecule becomes slightly polar for an instant.

The dispersion force (also London dispersion force) is a temporary attractive interaction formed when the electrons in two atoms occupy positions that make them temporary dipoles. As a result, these nonpolar molecules become slightly polar and can form temporal dipole-dipole interactions.