What does oxidation refer to in a chemical reaction?

In a chemical reaction, oxidation refers specifically to the process of losing electrons. When a substance undergoes oxidation, it increases its oxidation state as it loses negatively charged electrons. This is a fundamental concept in redox (reduction-oxidation) reactions, where oxidation and reduction occur simultaneously.

The loss of electrons can be observed in various reactions, such as those involving metals reacting with oxygen to form oxides. For example, when iron oxidizes, it loses electrons to oxygen, resulting in the formation of iron oxide (rust). This loss of electrons is clearly associated with an increase in the positive charge of the iron ions, correlating with the definition of oxidation.

In contrast, gaining electrons is referred to as reduction, which decreases the oxidation state of the substance. Understanding oxidation in this way helps to clarify its role in various chemical processes, including battery reactions, corrosion, and metabolic pathways in biology.