Structure, a necessary element for an understanding of chemistry, has not been precisely defined, in molecular detail, for the surface species formed at a solid-gas interface. Dramatic advances in theory, instruments and experimental procedures have now provided the surface scientists with an impressive arsenal of structural and electronic probes. Chemistry in the form of the classic displacement reaction can also provide an insight to the structure of surface compounds. In fact, many of the experimental procedures and systematics of the coordination and organometallic chemist can be effectively utilized in a complementary fashion with surface physics techniques to gain a more definitive picture of chemisorption states and or reactions at a surface.