- Sodium (Na) is a soft, silvery-white alkali metal with atomic number 11, positioned in Group 1 of the periodic table.
- It has one valence electron in its outermost shell, making it highly reactive and prone to forming ionic compounds. Its atomic structure consists of eleven protons, typically twelve neutrons, and eleven electrons arranged in three shells (two in the first shell, eight in the second, and one in the third).
- Sodium has only one stable isotope, sodium-23 (²³Na), although several radioactive isotopes are known, all with short half-lives.
- Under standard conditions, sodium is solid, soft enough to be cut with a knife, and has a metallic luster that quickly dulls upon exposure to air due to oxidation.
- Sodium is relatively abundant in the universe, formed through stellar nucleosynthesis in massive stars via the neon-sodium cycle. On Earth, it is the sixth most abundant element by mass and is widely distributed in minerals such as halite (NaCl), soda ash (Na₂CO₃), and cryolite (Na₃AlF₆). Due to its reactivity, sodium is never found in its pure elemental form in nature but exists primarily as salts dissolved in oceans and lakes, with sodium chloride being the main constituent of seawater salinity.
- The element was first isolated in 1807 by English chemist Sir Humphry Davy through the electrolysis of molten sodium hydroxide (NaOH). Davy named it “sodium” after the English word “soda,” referring to soda ash, while its chemical symbol “Na” comes from the Latin natrium, an old term for sodium carbonate.
- Sodium plays a critical role in both biological and industrial contexts. In living organisms, sodium ions (Na⁺) are essential for nerve impulse transmission, muscle contraction, and maintaining fluid balance through the sodium-potassium pump mechanism. In industry, elemental sodium is used in the synthesis of organic compounds, in metallurgy for refining reactive metals such as zirconium and potassium, and as a heat transfer agent in certain nuclear reactors due to its high thermal conductivity and low neutron absorption. Sodium vapor lamps, producing a bright yellow light, are widely used for street lighting.
- Chemically, sodium is extremely reactive, especially with water, producing sodium hydroxide and hydrogen gas in a vigorous, exothermic reaction that often ignites the hydrogen. It reacts with halogens to form ionic salts and with many nonmetals and organics under controlled conditions. Its compounds, particularly sodium chloride, sodium carbonate, and sodium hydroxide, are among the most important industrial chemicals, with applications in food preservation, glass manufacturing, paper production, and soap making.
- While sodium is essential for life, excessive sodium intake, particularly in the form of sodium chloride, is associated with high blood pressure and increased risk of cardiovascular diseases. Elemental sodium is hazardous, requiring storage under oil or in inert atmospheres to prevent reactions with moisture and oxygen. Contact with elemental sodium can cause severe burns due to its caustic reaction products.
