Aqueous solvation of tetrabutyl ammonium fluoride and iodide was investigated by means of 
molecular dynamics simulations in extended slab geometry. The varying propensities of 
the individual ions for the air/water interface were quantified and analyzed in terms 
of hydrophobic, polarization, and ion-ion interactions. While the cations behave as 
standard ionic surfactants the surface behavior of the halide counter-ions strongly 
depends on the ionic polarizability . iodide is surface active, while fluoride is repelled 
from the interface. The counter-ion effects at different concentrations on the density and 
charge profiles across the aqueous slab are discussed in detail.