Metal + Oxygen → Metal oxide Metal oxides are basic in nature. Therefore, Na2O, MgO and CaO are basic in nature. ZnO is amphoteric in nature i.e., it can react with both acids as well as alkalis to form salt. ZnO+2‌HCl→ZnCl2+H2O ∴ Basic oxides are Na2O,MgO,CaO,ZnO.