fémion

Fémion is a term used to describe a metal ion, a positively charged species formed from a metal atom by loss of electrons, or, in some cases, by complexation that yields a cationic form. Most fémion species carry a positive charge, written as M^n+, with oxidation states commonly in the range +1 to +3 for many elements, though higher states exist in specific environments. In aqueous solution, fémions are typically hydrated, forming solvated complexes such as [M(H2O)6]^n+. The charge and size of a fémion influence its preferred coordination, reactivity, and geometry, which can be octahedral or tetrahedral depending on the metal and ligands.

Common metal ions include sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), iron (Fe2+/Fe3+), copper (Cu2+), zinc (Zn2+), and manganese (Mn2+). They play central roles in chemistry, biology, and environmental processes. Metal ions act as catalysts in chemical reactions, stabilize structures, and participate in electron transfer. In biology, iron, magnesium, calcium, zinc, and copper ions serve as enzymatic cofactors and structural elements; for example, Fe2+/Fe3+ participates in oxygen transport and redox reactions, while Mg2+ supports ATP stability and ribosome function. Environmental and geological contexts consider metal ions in nutrient cycling, solubility, and toxicity at elevated concentrations.

Analytical methods commonly used to measure fémions include atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and ion chromatography. In industry, metal ions feature in electrolytes, catalysis, materials synthesis, and trace analysis, making them a fundamental topic across chemistry and biology.