What is Oxidation?

A molecule, atom, or iron undergoes oxidation when one or more of its electrons are lost, changing the chemical structure of the resulting compound. It is the opposite of reduction, which is a chemical reaction in which a molecule, atom, or ion gains electrons.

Oxidation reactions are common in everyday life and are important in many chemical processes, such as the rusting of iron and the browning of food. They can also be hazardous, as in the case of oxidative stress, which is a condition in which the body has an excessive amount of dangerous reactive oxygen species (ROS), which can destroy cells and aid in the onset of diseases like cancer and heart disease. 

Oxidation reactions often involve the transfer of oxygen atoms or the addition of oxygen to a molecule. For instance, when iron rusts, it combines with airborne oxygen to produce iron oxide (Fe2O3). Similarly, when food browns, it reacts with oxygen in the air to form a variety of different compounds, depending on the specific food and the conditions it is exposed to.

Oxidation reactions can be catalyzed (accelerated) by certain substances called oxidizing agents, which donate oxygen atoms or accept electrons from other substances. Some common oxidizing agents include oxygen (O2), hydrogen peroxide (H2O2), and ozone (O3).

An atom or compound undergoes oxidation, which alters its characteristics. An iron object, for instance, changes as it oxidizes because it has lost electrons. While oxidized iron is a brittle, reddish powder, unoxidized iron is a strong, structurally sound metal. The graphic below shows what happens to an iron atom during oxidation:

iron oxidation

Iron now possesses a charge once it has undergone oxidation. It now has a positive charge of three due to the fact that it lost three electrons. The number three and a positive sign (3+) printed as a superscript to the right of the Iron (Fe) symbol stand for this positive three charge.