We report new analytical results for the behaviour of the free energy of an ion between two media that are characterized by different dielectric permitivities including the ion polarizability as a phenomenological parameter. The differences in the free energy induced by the new terms related to the polarizability are on the order of a few k(B)T (similar to 25 meV), k(B) being the Boltzmann constant and T the temperature of the system not far from the room temperature, and may explain the enhanced propensity of halogen anions for the water-air or water-lipid interfaces with increasing ionic polarizability. (C) 2010 Elsevier B.V. All rights reserved.