Which type of force is present in all molecules and arises from temporary dipoles?

• A. Covalent bonding
• B. Ionic bonding
• C. London dispersion forces
• D. Metallic bonding

Answer: (C)

The idea being tested is how weak intermolecular attractions arise from fluctuations in electron distribution. In any molecule, the electrons are constantly moving, creating momentary regions of slight negative or positive charge—temporary dipoles. These fleeting dipoles can induce dipoles in neighboring molecules, and the two then attract each other. This mechanism is London dispersion forces, a type of van der Waals force that exists in all molecules, even nonpolar ones. They are generally weak but become stronger as the molecule’s electrons and size increase (more easily polarizable electron clouds and more surface area for contact). Covalent, ionic, and metallic bonds are stronger, involve more permanent connections, and do not describe these temporary, intermolecular attractions.