(Polar molecules, Non-polar molecules, etc.)
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van der waals forces is a general term that includes all intermolecular forces. London dispersion forces is a type of van der waals force that occurs between nonpolar molecules with instantaneously occuring dipoles.
An example of a van der waal force would be that of a sample of Helium. Essentially, it has a full valence shell and it would have a momentary dipole (one side of atom is positive and the other side is negative), therefore another helium atom could interact with its positive portion to the negative portion of the first helium atom. Basically, most substances can utilize van der Waal interactions and it is the weakest intermolecular reaction.
London Dispersion Force (LDF) is a weak intermolecular force caused by the distribution of elections in the electron cloud of atoms. Hence, because all atoms have electron clouds including noble gases, noble gases can have LDF with other atoms. Moreover, whether molecules are polar or non polar, LDF exist due to the distortion of each atom's electron cloud.
An example for a Van der Waals interaction would be between N2 molecules. They do not have an inherent dipole moment beween the two atoms as they are identical, however, there is an instantaneous dipole created due to a shift in the electron density distribution, which thereby induces a dipole moment between neighboring molecules. London dispersion forces are just a type of Van der Waals interaction.
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