What is called homologous series ? Give any three of its characteristics .

Explanation

Homologous series is a group or a class of organic compounds having same general formula & similar chemical properties in which the successive numbers differ by a `-CH_2 ` groups .
Characteristics of homologous series :
(i) Each member of the series differs from the preceding or succeeding member by one methylene group `(-CH_2)` and hence by a molecular mass of 14 amu .
(ii) All members of a homologous series contain the same elements and functional group .
(iii) They are represented by a general molecular formula. Eg : Alkanes , `C_nH_(2n+2)` .
(iv ) The members in each homologous series show a regular gradation in their physical properties with respect to their increase in molecular mass .
(v) Chemical properties of the members of a homologous series are similar.
(vi) All the members can be prepared by a common method.