Oxygen, the first element in group vi of periodic table has eight electrons which are distributed in orbital as follows      

It forms a wide range of ionic and covalent compound and it is the only element of group VI which forms multiple bonds with itself.


Thermal decomposition of potassium trioxochlorate(v) (KClO3): KClO3, when heated releases all of its oxygen in the presence of MnO2 as catalyst.

2KClO3         MnO2                                               2KCl(s) + 3O2(g)

Decomposition of hydrogen peroxide H2O2: H2O2 decompose in the presence of a catalyst, MnO2, to liberate oxygen without heating.           

2H2O2(l)         MnO2                                               2H2O(l) + O2(g) 


Oxygen is prepared on a large scale by fractional distillation of air.

  • Air is freed from CO2 using caustic soda
  • Followed by removal of dust particles and water vapour
  • It is the compressed to about 200atm
  • Then cooled compressed air is allowed to expand through a jet
  • Cooled air is allowed to cool more with incoming air
  • Continuous process of compression and expansion at temperature -2200C result in the liquefaction of air
  • Liquefied air id fractionally distilled. Light noble gas are first obtained
  • Follow by Nitrogen that boils at a temperature of -1960C (77K)
  • It will remain oxygen that boils at -1830C (90K)

Oxygen is then dried, compressed, stored in steel cylinder.

Properties of Oxygen

Physical properties

It is a colourless, odourless and neutral gas.

It is slightly soluble in water

It is slightly denser than air

It has a low boiling point of -1830C (77K)

This makes it difficult to liquefy oxygen.

Oxygen solidifies at -2250C (48K)

Chemical properties of Oxygen

  • It is stable to heat
  • It does not burn
  • Its solution in water is neutral to litmus
  • It supports combustion very vigorously
  • Direct combination with other elements:

 With metals: Oxygen reacts with metals to give basic oxides.

4Na(s) + O2(g)                            2Na2O(s)

2Ca + O2(g)                        2CaO

When sodium and potassium are heated in a plentiful supply, higher oxides are formed instead of the basic oxide.

4Na(s) + 2O(g)                     2Na2O2

4K(s) + 2O2(g)                                2K2O2

Others metals that react/burn in oxygen are:

2Mg + O2(g)                      2MgO

3Fe(s) + 2O(g)                                     FeO.Fe2O3

With Non-Metals: Oxygen combines with non-metal to form acidic oxide.

S(s) + O2(g)                   SO2

P4(s) + 3O2(g)                        P4O6(s)

P4(s) + 5O2(g)                 P4O10(g)

C(s) + O2(g)                     CO2(g)

  • Most hydrocarbons burn in oxygen to form carbon(iv)oxide and water.

CH4 + 2O2(g)                            CO2(g) + 2H2O(g)

          Test for Oxygen

Oxygen rekindles a glowing splint of wood. Nitrogen(I)oxide is the only gas that has similar chemical test with oxygen.

Uses of Oxygen

  1. Oxygen from air is used for breathing
  2. Oxygen is used by divers
  3. It is used for resuscitating fainting patients.
  4. Oxygen is a component of oxy-ethyne flame which is used, in welding and cutting metals.
  5. Oxy-hydrogen flame is used for cutting metals under water.
  6. Liquid oxygen and fuels are used as propellant for space rockets
  7. Oxygen is used in the steel industry for the removal of carbon, sulphur and phosphorus.
  8. Oxygen is used in the Linz-Donawitz process for making steel. 


Step 1: The teacher introduces the lesson to the students by asking them to write electronic configuration of oxygen

Step 2: The teacher explains the preparation of oxygen

Step 3: The teacher explains the properties of oxygen

Step 4: Students are allowed to ask questions on what they have learnt for clarity

Step 5: Teacher copies note on chalkboard while the students copies

EVALUATION:  How do you prepare oxygen industrially?

                           Mention 3 properties of oxygen                         

ASSIGNMENT: List the types of oxides with suitable examples