What is a redox reaction?

A redox reaction, short for reduction-oxidation reaction, is defined as a chemical reaction in which the oxidation states of atoms change due to the transfer of electrons between species. In these reactions, one substance undergoes oxidation (losing electrons) while another undergoes reduction (gaining electrons). This transfer of electrons is fundamental to many chemical processes, including combustion, respiration, and the functioning of batteries.

Understanding this concept is essential because electron transfer is a key characteristic that differentiates redox reactions from other types of chemical reactions, such as acid-base reactions, which typically involve the exchange of protons rather than electrons. Therefore, the emphasis on electron transfer in the correct answer highlights the significance of oxidation and reduction processes in various chemical contexts. The other options do not encompass the core definition of redox reactions, distinguishing them from those that involve proton transfer, specific types of compounds, or claims about energy changes that do not apply to all redox processes.