Sodium /ˈsoʊdiəm/ is a chemical element with symbol Na (from New Latin natrium) and atomic number 11.It is a soft, silver-white, highly reactive metal.odium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Many sodium compounds are useful, such as sodium hydroxide (lye) for soap-making and sodium chloride for use as a de-icing agent and a nutrient (edible salt). Sodium is an essential element for all animals and some plants.