kalíum

Kalíum, also spelled kalium, is a chemical element with the symbol K and atomic number 19. It is a soft, silvery‑white alkali metal in group 1 of the periodic table. Kalíum is highly reactive, tarnishes in air, and must be stored under oil or in an inert atmosphere. It has a low density and a low melting point of about 63.5°C. In chemistry it most commonly adopts the +1 oxidation state and forms a wide range of compounds, such as potassium chloride (KCl), potassium hydroxide (KOH), and potassium carbonate (K2CO3).

Natural occurrence and production. Kalíum is abundant in the Earth’s crust and occurs mainly in minerals and brines, including sylvite (KCl) and carnallite (KMgCl3·6H2O). It is also present in seawater as dissolved ions. Industrial production relies on mining and processing potash minerals or brines to obtain potassium salts; these salts can be refined or subjected to electrolysis in some processes to produce metal or specialty compounds.

Isotopes and biology. Naturally occurring kalíum consists predominantly of the stable isotopes 39K and 41K, with a small fraction of radioactive 40K, which decays very slowly. Potassium is an essential nutrient for most living organisms, playing a key role in nerve signaling, muscle function, heart rhythm, enzyme activity, and maintaining cell turgor and osmotic balance. Dietary intake is typically from fruits, vegetables, and dairy products.

Safety and uses. As a reactive metal, kalíum is handled with care to avoid contact with moisture. The most important commercial uses are in fertilizers, notably potassium chloride and potassium sulfate, which supply potassium to crops and, indirectly, to the food chain. Excessive potassium intake or impaired excretion can be harmful to humans.