katyon

A katyon, usually spelled cation in English, is a positively charged ion. The term is used in many languages (for example Turkish and several Slavic languages) with the same meaning. Cations form when atoms or molecules lose one or more electrons, resulting in a net positive charge that is attracted to the negatively charged electrode in electrochemical cells.

Cations can be monoatomic, such as sodium (Na+), potassium (K+), calcium (Ca2+), and iron in various oxidation states, or polyatomic, such as ammonium (NH4+) and hydronium (H3O+). The charge, or valence, of a cation depends on how many electrons have been removed. In salts, cations are balanced by anions to form electrically neutral compounds, for example sodium chloride (NaCl) or calcium sulfate (CaSO4).

In biological systems, several cations play essential roles. Sodium (Na+) and potassium (K+) coordinate nerve impulses and fluid balance, calcium (Ca2+) is important for bone structure and signaling, and magnesium (Mg2+) plays a key role in enzyme activity and energy transfer. In chemistry and industry, cations are central to electroplating, battery chemistry (lithium, nickel, cobalt cations), and a wide range of synthesis and catalysis processes.

Cations are often referred to in contrast to anions, which are negatively charged ions. The behavior of cations—such as their hydration in solution, coordination chemistry, and complex formation—depends on factors including ionic radius, charge density, and the surrounding chemical environment.