When a chemical substance has either lost an electron or gained an oxygen?

When a chemical substance has either lost an electron or gained an oxygen, it has undergone a chemical change known as oxidation.

• Loss of an Electron (Oxidation): When a substance loses an electron, it is said to be oxidized. The process of oxidation involves the increase in the oxidation state or the loss of electrons by an atom, ion, or molecule.
• Gaining an Oxygen (Oxidation): In many cases, gaining an oxygen is associated with oxidation as well. For example, if a substance gains oxygen, it often involves the removal of electrons from another substance, indicating an oxidation reaction.

These concepts are fundamental in redox (reduction-oxidation) reactions, where one substance undergoes oxidation (loses electrons) and another substance undergoes reduction (gains electrons). The substance that loses electrons is referred to as the reducing agent, and the substance that gains electrons is the oxidizing agent.