What is the definition of oxidation in chemical reactions?

Oxidation in chemical reactions is defined as the process in which a substance loses electrons or experiences an increase in its oxidation state. This change is fundamental to redox (reduction-oxidation) reactions, where one species is oxidized and another is reduced. When a substance loses electrons, it often results in the formation of a more positively charged ion, thereby increasing its oxidation state.

For instance, consider the oxidation of iron when it reacts with oxygen to form iron(III) oxide. Iron goes from an oxidation state of 0 in its elemental form to +3 in iron(III) oxide as it loses electrons during the reaction. This transformation illustrates the concept of oxidation effectively.

Other options present definitions that do not accurately capture the essence of oxidation. Gaining electrons or decreasing oxidation state refers to reduction, while the formation of compounds from elements represents a different type of reaction, often not directly related to oxidation. Similarly, the reaction between an acid and a base describes acid-base neutralization, a distinct class of reactions that do not necessarily involve oxidation or reduction processes. Understanding these distinctions helps clarify the precise meaning of oxidation in chemistry.