Exptl. evidence is presented that abstraction is a common mechanism (~50%) in the dissociative chemisorption of O₂ on Al(111) at a translational energy of 0.5 eV. As a result of this mechanism, individual isolated O-atoms are obsd. in STM. At this translational energy ordinary dissociative chemisorption processes also occur, resulting in pairs of adatoms. The ejected O-atoms originating from the abstraction reaction are detected in the gas phase using laser spectrometry. Together, these observations provide compelling evidence for the abstraction mechanism.