The decomposition of N2O through oxygen abstraction and surface peroxide ion formation is studied over the whole sequence, MgO-BaO, of alkaline-earth rock-salt metal oxides. The initial barrier to abstraction follows the expectations (MgO > CaO > SrO > BaO) of O2- chemistry. Good agreement with experiment is obtained for MgO and CaO, but for BaO the discrepancy is large. Consideration of both the Langmuir-Hinshelwood and the Elay-Rideal mechanisms suggests that for MgO the surface is regenerated already at low peroxide ion coverage through diffusion and recombination. For CaO, diffusion is hindered and recombination probably occurs only at higher peroxide ion coverage obtained through deposition of oxygen. SrO and BaO allow neither diffusion over the surface nor recombination of oxygen from two surface peroxide ions. Instead, the Elay-Rideal mechanism becomes active with activation energy at high coverage in good agreement with the experiment for BaO.