Solution:concept - All elements are made up of a single type of atom. These elements are represented by a chemical symbol in a periodic table. Each symbol represents a unique element.
Na is the sodium element; its symbol is derived from its Latin name ‘Natrium’ and it belongs to the 1st group and 3rd period of the periodic table. Its atomic number is 11 and its atomic mass is 23.
Sodium has a strong metallic lustre. At normal temperatures, it is so soft that it can be shaped into leaves with the pressure of the fingers. Sodium compounds fade rapidly on exposure to air, although less rapidly than potassium. Sodium metal is highly reactive and it catches fire when kept open, that is why it is stored in kerosene oil.
Thus, the symbol Na represents Sodium.
Hence, the correct answer is 3.