When theelectronegativity differencein a chemical bond is significant, the electron density is strongly skewed, which produces a permanent dipole. Permanent dipole-dipole forces arise when the negative part of one dipole attracts the positive part of another dipole.

The strength of permanent dipole-dipole forces depends on the strength of each individual dipole andthe geometry of the molecule. An example of how geometry plays a role is thefluoromethanes.

Examples of compounds with permanent dipoles include halogen methanes, ketones like acetone, andwater. Water contains a specific subcategory of permanent dipole-dipole forces known ashydrogen bonding.

Figure 1: Diagram showing how the molecular dipoles in two atoms give rise to permanent dipole-dipole forces