All salt contains two basic elements: sodium and chlorine. Sodium (chemical symbol Na) is a silvery-white metal that reacts violently when mixed with water and oxidises in air. Chlorine (chemical symbol Cl) is greenish-yellow and exists as a gas at room temperature. Because both elements are so volatile, they’re found in nature as part of compounds like sodium chloride (NaCl), which forms the mineral halite. Sodium chloride is about 60 percent chlorine and 40 percent sodium [source: Salt Institute]. Although sodium is volatile and chlorine is toxic, together as sodium chloride they’re integral to life. Sodium chloride molecules are cubical. The large chloride ions are closely packed together, with smaller sodium ions filling in the spaces between them.