In this Perspective, we highlight some recent progress in the reactive scattering of "chemical probe" species such as atoms or small radicals from liquid surfaces. We emphasize in particular the evolution of this area from purely dynamical studies of the scattering mechanism. The mechanistic understanding that has now been gained is sufficiently mature to allow the same methods to be used as an effective analytical tool. The use of this approach to measure liquid-surface composition and structure is illustrated through the scattering of O(3P) atoms from a common, imidazolium-based family of ionic liquids. © 2010 American Chemical Society.