Sodium is a highly reactive alkali metal with the atomic number 11. It is a soft, silvery-white metal that is known for its extreme reactivity with water. Sodium is essential for various biological processes in living organisms, including nerve function and muscle contractions. It is also used industrially in the production of chemicals, including sodium hydroxide (caustic soda) and sodium carbonate (soda ash).

In its pure form, sodium is stored under oil to prevent contact with air and moisture, as it can ignite or explode when exposed to water. Sodium is a critical element in the diet and is obtained from table salt (sodium chloride). However, excessive sodium intake can have adverse effects on health, such as high blood pressure. Sodium compounds are also used in various industrial applications, including the manufacture of detergents, paper, and textiles.