The chemical element with the symbol Na is sodium. Sodium is an essential element represented by atomic number 11 on the periodic table. It belongs to the alkali metal group and is characterized by its highly reactive nature, particularly with water, where it forms sodium hydroxide and hydrogen gas. Sodium plays a critical role in various biological functions, including nerve transmission and maintaining fluid balance in the body. It is commonly found in nature combined with other elements, mainly in the form of sodium chloride, or table salt, which is widely used in food and preservation processes.