1 of 2



Oxygen combines with elements to form oxides which are binary compounds of oxygen that can be classified into four groups:

  1. Acidic Oxide
  2. Basic Oxide
  3. Amphoteric Oxide
  4. Neutral Oxide

In addition, there are peroxides and other higher oxides.

a. Acidic Oxides

These are oxides of non-metals which react with water to produce acids. They also react with alkalis to form salt and water only. Oxides of non-metals which react with water to form acids are called anhydrides.

e.g.      CO2 + H2O                  H2CO3


            SO2 + H2O                  H2SO3(aq)


            SO3(g) + H2O                 H2SO4


            P4O10(s) + 6H2O(l)                        4H3PO4(aq)


            2NO2(g) + H2O(l)                       HNO3 + HNO2          

                                    trioxonitrate(v) and dioxonitrate(iii)

With Alkalis

CO2(g) + 2KOH(aq)                      K2CO3(aq) + H2O(l)

SO2(g) + 2KOH(aq)                        K2SO4(aq) + H2O(l)

SO3(g) + 2NaOH(aq)                               Na2SO4(aq) + H2O(l)

b. Basic Oxide:

These are oxides of metals which react with acids to form salt and water only.

e.g. Sodium oxide       Na2O

       Potassium oxide   K2O

       Magnesium oxide MgO

Copper(ii)oxide           CuO

       Calcium oxide                  CaO

They react with acids to form a salt and water only.

Na2O + 2HCl(aq)                                   2NaCl(aq) + H2O(l)

K2O + 2HCl(aq)                                    2KCl(aq) + H2O(l)

2CaO + 2HNO3                      Ca(NO3)2(aq) + H2O(l)

c. Amphoteric oxides:

Are metallic oxides which can react with both acids and alkalis to produce salt and water only.

With acids, amphoteric acids behave as bases, forming a salt and water only.

ZnO(s) + H2SO4(aq)                                          ZnSO4(aq) + H2O(l)

Al2O3 + 6HCl(aq)                                   2Al(Cl)3(aq) + 3H2O(l)

PbO(s) + H2SO4(aq)                             PbSO4(s) + H2O(l)

e.g.      Zinc oxide       ZnO

            Aluminium oxide        Al2O3

            Lead(ii)oxide  PbO

            Tin(iv)oxide    SnO2

With alkalis, they behave like acids and exhibit acidic property by forming complex salts.

ZnO(g) + 2NaOH(aq) + H2O(l)                                         Na2Zn(OH)4


Al2O3(s) + 2NaOH(aq) + 3H2O                                         2NaAl(OH)4(aq)


PbO(s) + 2NaOH(aq) + H2O(l)                                  Na2Pb(OH)4(aq)


  • Neutral oxide:

These are oxides of non-metal show neither acidic nor basic properties/behaviour.


Nitrogen(I)oxide                     N2O

Carbon(ii)oxide                       CO

         Water                             H2O

EVALUATION:  mention 5 types of oxides with examples

                           Mention 3 properties of oxygen                         

ASSIGNMENT:  how is ozone produced