Определить валентность: Na2O, NO, CO2, PbO2, BaO, P2O3, N2O3, Mn2O7, PbO, SeO3, Ag2O, CaO, N2O5, Cu2O, SO3, ZnO, CuO, NO2, SO2, SO3, Cr2O3, Li2O, Fe2O3, Cl2O7, FeO, Cl2O, SiO2, CrO3, P2O5, MgO, N2O5, SnO, CO, N2O, P2O5, SnO2, A...