The element with the chemical symbol Na is sodium. Sodium is a highly reactive metal belonging to the alkali metal group in the periodic table. It is found in significant quantities in nature, primarily in the form of sodium chloride, or table salt. Sodium is essential for various biological processes, including nerve function and fluid balance in living organisms. It reacts vigorously with water, producing hydrogen gas, and is typically stored in oil to prevent such reactions. Due to its reactivity, sodium does not exist freely in nature but rather in compounds.