sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery‑white alkali metal that readily tarnishes in air and reacts vigorously with water. In nature it is not found free; it occurs mainly in compounds such as sodium chloride (halite) and in various silicates and carbonates. In the oceans, sodium ions (Na+) are the most abundant dissolved cations.

Sodium metal has a low density and a melting point of 97.72°C. It forms oxides and peroxides with oxygen and reacts violently with water, producing sodium hydroxide and hydrogen gas.

Commercial production is primarily by electrolysis of molten sodium chloride in chlor-alkali processes. The name sodium derives from the Latin natrium.

Uses include the production of sodium hydroxide, sodium carbonate, and other sodium compounds used in chemicals, glassmaking, papermaking, and detergents. Sodium chloride remains essential as table salt and a food preservative. Sodium metal is used as a reducing agent in certain chemical syntheses, and sodium-vapor lamps emit characteristic yellow light.

Biologically, sodium ions are essential electrolytes in animals and humans, involved in maintaining fluid balance, nerve impulse transmission, and muscle function. Dietary intake is tightly regulated; excessive intake is linked to hypertension and cardiovascular risk.

Safety: As a reactive metal, sodium must be stored away from moisture and oxidizing agents, typically under oil. Reactions with water are exothermic and can ignite or explode if metal is concentrated.