Van der Waals Forces

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np [Johannes D. van der Waals † 1923 Dutch physicist] (1926) (secondary valence force, intermolecular force) An attractive force, much weaker than primary covalence bonds, between molecules of a substance in which all the primary valences are saturated. They are believed to arise mainly from the dispersion effect, in which temporary dipoles induce other dipoles in phase with themselves. The primary van der Waals forces are dipole-dipole (polar molecules) and London forces (nonpolar molecules). These forces are attributed to the attractions between molecules and from noncovalent bonds (Goldberg, D. E., Fundamentals of Chemistry, McGraw-Hill Science/Engineering/Math, New York, 2003).