ΓΌ  Oxides of Nitrogen: Nitrogen forms a number of oxides in different oxidation states. They are:
·       N2O → Laughing gas (Nitrous oxide). N = N → O
It is prepared by the action of any lighter metal with very dil. HNO3
4Sn(s) + 10HNO3 → 4Sn(NO3)2 + 5H2O + N2O

·       NO → Nitric oxide. It is prepared by treating sodium nitrite with acidified ferrous sulphate.
 2NaNO2 + 2FeSO4 + 3H2SO4 → Fe2(SO4)3 + 2NaHSO4 + 2H2O + 2NO



·       N2O3 → Dinitrogen tetroxide.
It is prepared by treating nitric oxide with dinitrogen tetroxide at 250K.
2NO + N2O4   → 2 N2O


·       NO2 → Nitrogen dioxide.
It is prepared by heating lead nitrate at about 673K.
2Pb(NO3)2 → 4 NO2 + 2 PbO + O2
It is an acidic brown gas. Its structure is:



·       N2O4 (dimer of NO2) → dinitrogen tetraoxide.
It is prepared by cooling NO2. It is a colourless solid or liquid with acidic character. Its structure is:


·       N2O5 → Dinitrogen pentoxide.It is prepared by nitric acid with phosphorus
pentoxide.
4 HNO3 + P4O10 → 4 HPO3 + 2 N2O5                                
It is a colourless solid with acidic character. Its structure is: