The chemical element with the symbol "Na" is sodium. Sodium is a highly reactive metal and is classified as an alkali metal in group 1 of the periodic table. It is essential for various physiological functions in living organisms, including maintaining fluid balance, nerve transmission, and muscle contraction. Sodium is abundant in nature, particularly in the form of sodium chloride, or common table salt. While it is necessary for health, excessive sodium intake can lead to high blood pressure and other cardiovascular issues, underscoring the importance of moderation in consumption.