Neutral impact ion scattering spectroscopy (NICISS) is used to measure the depth profiles of ionic surfactants, counterions, and solvent molecules on the angstrom scale. The chosen surfactants are 0.010 m tetrahexylammonium bromide (THA(+)/Br-) and 0.0050 m sodium dodecyl sulfate (Na+/DS-) in the absence and presence of 0.30 m NaBr in liquid glycerol. NICISS determines the depth profiles of the elements C, O, Na, S, and Br through the loss in energy of 5 keV He atoms that travel into and out of the liquid, which is then converted into depth. In the absence of NaBr, we find that THA(+) and its Br- counterion segregate together because of charge attraction, forming a narrow double layer that is 10 angstrom wide and 150 times more concentrated than in the bulk. With the addition of NaBr, THA(+) is "salted out" to the surface, increasing the interfacial Br- concentration by 3-fold and spreading the anions over a similar to 30 angstrom depth. Added NaBr similarly increases the interfacial concentration of DS- ions and broadens their positions. Conversely, the dissolved Br- ions are significantly depleted over a depth of 0-40 angstrom from the surface because of charge repulsion from DS- ions within the interfacial region. These different interfacial Brpropensities correlate with previously measured gas-liquid reactivities: gaseous Cl-2 readily reacts with Br- ions in the presence of THA(+) but drops 70-fold in the presence of DS-, demonstrating that surfactant headgroup charge controls the reactivity of Br- through changes in its depth profile.