1)4Na + O2 = 2Na2O
2)Na2O + H2O → 2 NaOH
3)NaOH + HCl → NaCl + H2O
4)NaCl + H2SO4 → Na2SO4 + HCl
H2S H(I) S(II)
Fe2O3 Fe(III) O(II)
N2O5 N(V) O(II)
NH3 N(III) H(I)
Cl2O7 Cl(VII) O(II)
OF2 O(II) F(I)
MgO Mg(II) O(II)