What is a homologous series?

A homologous series is defined as a family of compounds that share the same general formula and exhibit similar chemical properties. The members of a homologous series differ from one another by a specific unit, usually a -CH2- group, and they display a predictable pattern in their physical properties, such as boiling points and melting points, as their molecular size increases.

The consistency of the general formula signifies that all the compounds within the series maintain similar types of bonds and functional groups, leading to comparable reactivity and behavior during chemical reactions. This concept is particularly significant in organic chemistry, where various homologous series, such as alkanes, alkenes, and alcohols, can be characterized based on their structural similarities and trends in their properties.

The other answers do not fully capture the essence of a homologous series. For instance, stating that it is a series of compounds with different formulas misses the crucial aspect of the common general formula, which is essential to the definition. Describing it as a sequence of elements in the periodic table is misleading, as the concept applies specifically to groups of organic compounds rather than elemental organization. A group of compounds that all react similarly is also a broader statement that does not emphasize the systematic structure and general formula characteristic of