In this study, we have compared the results of using chemical probes on model surfaces to investigate reactivity of monolayer Ni films on Pt(111), W(110), and Ru(0001) single crystal surfaces. Using H-2, cyclohexene, and ethylene as probe molecules, we have studied the metal-H bond strength, the hydrogenation of cyclohexene, and the bonding and decomposition of ethylene. The Ni/Pt(111) and Ni/W(110) surfaces exhibit a low-temperature desorption of hydrogen at monolayer Ni coverages [also at 0.4 ML for the Ni/W(110) surfaces]. In contrast, the presence of monolayer Ni on Ru(0001) does not induce the low-temperature desorption state of hydrogen on the Ni/Ru(0001) surface. This desorption at low temperature is an indication of a weaker metal-H bond, which will affect the hydrogenation activity of the surfaces. For example, on the 1 ML Ni/Pt(111) and the 0.4 ML Ni/W(110) surfaces, a low-temperature hydrogenation pathway is detected. Previous high-resolution electron energy loss spectroscopy results indicate that cyclohexene is weakly pi bonded to the Ni/Pt(111) surface, but it is strongly bonded to the Ni/W(110) surface. These results further confirm the importance of weakly bonded hydrogen for the enhancement of the hydrogenation pathway. Finally, the 1 ML Ni/Pt(111) surface is relatively inactive toward ethylene decomposition, while the 1 ML Ni/Ru(0001) surface remains active toward the dissociation of ethylene. (C) 2003 American Vacuum Society.