What is meant by the term homologous series in chemistry?

Homologous series refers to a group of organic compounds that share a common general formula and exhibit similar chemical properties due to their structural similarities. Each successive member of the series differs by a specific incremental unit, typically a -CH2- group. This means that as you move through the series, you can predict and identify trends in physical and chemical properties, such as boiling points or reactivity.

For example, in the series of alkanes (a type of hydrocarbons), each member has one more carbon atom than the previous one, following the general formula CnH2n+2. The close relationship between the members of a homologous series allows chemists to make educated predictions about the behaviors and reactions of substances within the series based on the properties of other members.

The other options lack this critical aspect: a group of non-metals does not imply a categorization based on the structural relationship among compounds; compounds with only single bonds may not belong to a single homologous series, and elements that react with water do not define a series based on structural or chemical similarities.