The reactions of hydrated monovalent transition metal ions M+(H2O)(n), M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Clusters containing monovalent chromium, cobalt, nickel, or zinc were reactive toward O-2, while only hydrated cobalt was reactive toward N2O. A strongly size dependent reactivity was observed. Chromium and cobalt react very slowly with carbon dioxide. Nanocalorimetric analysis, O-18(2) exchange, and collision induced dissociation (CID) experiments were done to learn more about the structure of the O-2 products. The thermochemistry for cobalt, nickel, and zinc is comparable to the formation of O-2(-) from hydrated electrons. These results suggest that cobalt, nickel, and zinc are forming M2+/O-2(-) ion pairs in the cluster, while chromium rather forms a covalently bound dioxygen complex in large clusters, followed by an exothermic dioxide formation in clusters with n <= 5. The results show that hydrated singly charged transition metal ions exhibit highly specific reactivities toward O-2, N2O, and CO2.