What is an homologous series? Explain with an example.

An homologous series is a group of organic compounds that share a similar structure and chemical properties because they have the same functional group and successive compounds in the series differ by a repeating unit. In simpler terms, these are families of organic compounds that have similar chemical properties and structures, with each member of the series differing by a common structural unit, often referred to as a "homologous unit."

The most common example of an homologous series is the alkane series. Alkanes are hydrocarbons with only single bonds between carbon atoms. The general formula for alkanes is CnH2n+2. In this series, each member differs from the next by a CH2 unit. For example:

Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10)
Pentane (C5H12)
In this series, each member differs by a CH2 unit, and they all possess similar properties due to their common functional group (single bonds between carbon atoms). Similarly, other homologous series include alkenes, alkynes, alcohols, carboxylic acids, and so on, each with their characteristic functional groups and repeating structural units.