In this contribution, we investigate the interaction between CO and O-2 with metal atoms of group 11 deposited on a defect-free magnesium oxide surface using density functional theory with periodic point charge embedding. We present the first transversal study of the adsorption and coadsorption of CO and O-2 on coinage metal adatoms deposited on metal oxide surfaces from the perspective of single-atom catalysis. Various analysis tools shed light on the binding situation of the metal atoms to the substrate as well as on the situation of the two molecules on the different metal centers. Our analysis demonstrates that cooperative electronic effects enhance the stability of CO upon coadsorption with O-2 for all three metal centers. Our results also explain the lack of catalytic activity of group 11 metal atoms with respect to CO oxidation under thermal conditions as a competition between OC-O-2 bond activation and surface diffusion, leading to metal atom agglomeration. Additionally, it is shown how coadsorption of CO and O-2 on Au/Mg(001) could pave the way to single atom photocatalysis.