Write a note on homologous series.

Explanation

(i) A series of organic compounds each containing a characteristic functional group and successive members differ from each other in molecular formula by a `CH_(2)` group is called homologous series.
(ii) e.g., Alkanes, Methane (`CH_(4)`), ethane (`C_(2)H_(4)`), Propane (`C_(3)H_(8)`) etc.
(iii) Compounds of the homologous series are represented by a general formula e.g., Alkanes `C_(n)H_(2n+2)` , Alkene `C_(n)H_(2n)`
(iv) They can be prepared by general methods
(v) They show regular gradation in physical properties but have almost similar chemical properties.