Natrium

Natrium is the Latin name for the chemical element with the symbol Na and atomic number 11. It is an alkali metal in group 1 of the periodic table, the lightest metal that forms stable compounds. It is a soft, silvery‑white metal, easily cut with a knife, and is the sixth‑most abundant element by weight in the Earth's crust. In seawater it exists mainly as the Na+ ion.

It has a density of about 0.97 g/cm3, melts at 97.72 C and boils at 883 C. It quickly tarnishes in air, forming a surface oxide, and is highly reactive, especially with water and oxygen.

Chemically, natrium reacts vigorously with water to produce hydrogen gas and sodium hydroxide. It forms a wide range of compounds, including sodium chloride (table salt), sodium carbonate, and sodium hydroxide. In air it forms oxides and peroxides under certain conditions.

Natrium occurs naturally in seawater and evaporite minerals such as halite (NaCl). Industrial production is achieved mainly by electrolysis of molten NaCl in the Downs process to yield sodium metal; chlor-alkali processes produce sodium hydroxide and chlorine gas.

In biology, sodium ions are essential extracellular cations involved in fluid balance, nerve impulses, and muscle function, via the sodium–potassium pump. Sodium compounds have wide uses in food, chemical manufacturing, glassmaking, and metallurgy.

The name natrium comes from Latin; the chemical symbol Na is derived from this name. Because of high reactivity, sodium metal is stored under oil or in an inert atmosphere to prevent contact with air and water.