The coadsorption of Zn with Cs (an electropositive species) or O (an electronegative species) on Ru(001) does not induce significant changes in the thermal stability of the Ru-Zn bond. On the other hand, two-dimensional CuZn (or AuZn) alloys in contact with Ru(001) show Ru-Zn and Zn-noble metal bonds more stable than the corresponding bonds in Zn/Ru(001) and thick CuZn (or AuZn) alloys. This phenomenon is caused by synergistic interactions in three-center metal-metal bonding. Photoemission studies indicate that at submonolayer coverages of Zn and O there is no lateral bonding between these species on Ru(001). The formation of ZnO(x) films on Ru(001) occurs when the Zn and O coverages are higher than 1 ML. On Zn films supported on Ru(001), the initial adsorption probability of O2 is extremely low, and O2 exposures in the range of 10(3)-10(4) L are necessary to produce a significant transformation of metallic Zn into ZnO. The presence of Cs enhances the oxidation rate of Zn by 2-3 orders of magnitude. In the Cs/Zn/Ru(001) systems, the alkali adatoms adsorb and dissociate O2 molecules, producing a reservoir of oxygen species that react with Zn.