Potassium

Potassium is a chemical element with the symbol K and atomic number 19. It is a soft, highly reactive alkali metal in group 1. In pure form it has a silvery luster but tarnishes rapidly in air and is stored under oil or in an inert atmosphere to prevent oxidation. Potassium reacts vigorously with water, producing hydrogen gas and a strongly alkaline solution.

Its melting point is 63.5°C and its boiling point 759°C. It forms oxides and peroxides in air and dissolves readily in water to give K+ and hydroxide. Most potassium compounds are ionic; the common natural form is the potassium ion, K+.

Potassium is abundant in the Earth's crust as minerals such as sylvite (KCl) and carnallite (KMgCl3·6H2O), and in seawater. Most commercial potassium comes from potash brines by evaporation and mining. Primary products include potassium chloride (KCl), potassium sulfate (K2SO4), and potassium hydroxide (KOH), used mainly in fertilizers and various chemical applications.

Biologically, potassium is an essential dietary mineral and the principal intracellular cation in humans and many other organisms. It supports nerve signaling, muscle contraction, and cellular osmotic and acid-base balance. The kidneys regulate potassium; both deficiency (hypokalemia) and excess (hyperkalemia) can cause serious health problems, with intake guidance varying by age and health status.

The symbol K derives from kalium, the Neo-Latin form of the Arabic qiāld? or Latin kalium. Potassium was isolated by Humphry Davy in 1807 by electrolysis of molten potash. The name reflects its source from potash and it has wide uses in fertilizers, chemistry, and industry.