Which of the following elements is represented by the symbol "Na"?

The element represented by the symbol "Na" is sodium. This symbol originates from the Latin word "Natrium," which is a term used for sodium in many languages. Sodium is an alkali metal and is essential for various biological functions in the human body, including fluid balance, nerve transmission, and muscle function. Its properties include being a soft, silvery-white, highly reactive metal that is typically found in nature only in compound form due to its reactivity.

In the context of the other options, nitrogen is represented by the symbol "N," a nonmetal that is pivotal for life, as it is a significant component of amino acids and nucleic acids. Noble gases, a group of elements characterized by their lack of reactivity due to filled valence electron shells, do not have a specific single symbol but include elements like helium and argon. Neon, another noble gas, is denoted by the symbol "Ne." Hence, sodium stands distinct from these other elements with its unique properties and applications, reinforcing that "Na" accurately corresponds to sodium.