Cationen

A cation, plural cations, is a positively charged ion formed when an atom or molecule loses one or more electrons. The positive charge is indicated by a superscript, as in Na+ or Ca2+. Cations are the counterparts of anions, which carry a negative charge. In electrochemical processes, cations are attracted to the negative electrode and migrate toward the cathode where they can gain electrons.

Common cations include alkali metals such as sodium (Na+), potassium (K+), and lithium (Li+); alkaline earth metals like calcium (Ca2+) and magnesium (Mg2+); and polyatomic cations such as ammonium (NH4+). Transition metals can form cations with various charges, for example Fe2+ and Fe3+.

Cations are produced in several ways: by ionization in solution, dissolution of salts, redox reactions that remove electrons, or complex formation with ligands. In solids, minerals, and solutions, cations balance the negative charges of anions to maintain electroneutrality. In soils, the cation exchange capacity describes the ability of clay minerals to exchange cations with the soil solution, influencing nutrient availability and fertility.

Nomenclature often reflects the oxidation state, as in Fe2+ or Fe3+. Cations can be monovalent, divalent, or trivalent, among other charges; transition metals may exhibit multiple oxidation states. In coordination chemistry, cations act as Lewis acids, binding ligands to form complexes.

Cations are central in biology, environment, and technology. They regulate nerve signaling and muscle contraction (e.g., Na+, K+, Ca2+), affect water hardness (Ca2+, Mg2+), and serve as charge carriers in batteries and electrolytic systems. Analytical methods such as flame tests, atomic absorption spectroscopy, and ion chromatography are used to detect and quantify cations.