The chemical element with the symbol "Na" is sodium. Sodium is an alkali metal and is characterized by its soft, silvery-white appearance and is highly reactive, especially with water. It is essential for various biological functions in living organisms, including fluid balance and nerve transmission. Sodium is commonly found in nature, primarily in the form of sodium chloride, or table salt. In industry, sodium is used in diverse applications, including the production of glass, chemicals, and as a heat exchanger in some nuclear reactors. Its reactivity necessitates careful handling, as it can be hazardous.