Class 6 Chemistry Air Around us Nitrogen


  • About four-fifth of air is nitrogen.

Uses of Nitrogen

  1. It is important for the growth of all living organisms.(Used in making proteins)


  1. It is used to fill air in tyres in vehicles.
  2. It is used in food packaging.
  3. Used for making chemical fertilizers and explosives.
  4. Also in the manufacture of stainless steel.

Nitrogen Fixation

  • Living organisms cannot use nitrogen from the atmosphere directly so it has to be fixed or combined.
  • The process of converting atmospheric nitrogen into useful soluble nitrates forms which can be used by plants is called nitrogen fixation.
  • Nitrogen Fixation is carried by
    1. Lighting:-
      • The enormous energy of the molecules breaks the molecules of nitrogen.
      • The nitrogen molecules combine with oxygen to form nitrogen oxides.
      • The nitrogen oxides dissolve in the rainwater to form soluble useful compounds like nitrates or ammonia.
      • These compounds come down along with rain water to the earth and seeps into the soil.
      • These plants absorb these nitrates along with water.
    2. Rhizobium Bacteria:
      • The Rhizobium bacteria infect the roots of leguminous plants like pea, fenugreek, soya bean etc.
      • The bacteria start multiplying in the root nodules.
      • They convert atmospheric nitrogen into useful nitrogen compounds like nitrogen/ammonia.
  •  Class_6_Air_Around_Us_Nitogen_Fixation
    1. Free living bacteria
      • For example blue green algae can convert atmospheric nitrogen into nitrates.


  • Decomposers
    1. They are organisms that break the dead and decaying plants and animals for humus.
    2. They play a very important role in nitrogen cycle. For example: - Fungi, earthworm, termites etc.
  • Different ways of increasing fertility of the soil
    1. By growing leguminous plants
    2. By adding chemical fertilizers like NPK (Nitrogen, phosphorous and Potassium).

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