Homologous series.

Question

Homologous series have same chemical property why?
Methane and ethane have different chemical property or not !If yes then
why just adding a hetero atom in both compound can make both compound having similar property.

Methane and ethane is homologous series or not ?

If yes the how ?

Methane and butane do not have hetero atom attached to it then why this is homologous series?

Answer 1

The definition of a homologous series of compounds is that these compounds have the same general formula with variations of a single parameter such as mass or molecular size. This is the case with methane, ethane and butane.  They are all straight-chained alkanes but because of the added bridge added for each member, they each have different di-pole moments and this causes them to have slightly different properties such as slightly different boiling points, and different masses etc..  By nature, all alkanes are not very reactive, like a tree, but one can hang other functional groups upon them like christmas ornaments  on the tree causing a "moiety". These little substructures or moieties and partial-functional groups are the things which can cause them (the original homologous series, the alkanes) to be more reactive, but by nature, they themselves are not and have only slightly different physical and/or chemical properties such as mass or boiling point...hope this makes some sense and helps.