Interactions between ions and induced non-polar molecules

4 Interactions between ions and induced non-polar molecules 

It is important to note that this is half of the pair potential that is expected for the interaction of an ion with a molecule having a permanent dipole moment (rotating) similarly aligned [V(r) = —aE2, compare with Equation (34) in Section 2.4.1]. Since some energy is taken up in polarizing a molecule to induce a dipole moment rather than having a permanent dipole moment, it is reasonable that a weaker pair potential is obtained for the interactions between ions and induced non-polar molecules. 

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Coulomb forces operate between ions in electrolyte solutions. Coulomb interactions are much longer range and stronger than van der Waals interactions. However this does not mean that van der Waals interactions can always be ignored in electrolyte solutions. As we saw in Section 2.4.1, there are interactions between ions and dipolar molecules in Section 2.5.4 interactions between ions and induced non-polar molecules and in Section 2.5.5 interactions between ions and induced polar molecules. All of these interactions affect the total interaction potential. 

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