Sodium

Despite SODIUM being too reactive to occur free in nature, it’s present in the Earth’s crust in many different compounds.
It’s a very familiar element as it forms many useful compounds. Some of the most common are: table salt (NaCl), soda ash (Na2CO3), baking soda (NaHCO3), caustic soda (NaOH) and borax (Na2B4O710H2O). Sodium vapor is used in streetlights, producing a brilliant yellow light.
Probably the best known compound among ancient civilizations was sodium carbonate (Na2CO3), commonly known as soda. Soda is one of the most common ores of sodium found in nature and it was used very early in human history to make glass. The Egyptians called soda natron, from which the Romans later derived the term natrium. It is from these names that sodium's modern chemical symbol, Na, is derived.

Sodium chloride is also abundant in seawater and brine. It can be obtained very easily from these sources simply by trapping the seawater or brine and allowing the water to evaporate. The technology for obtaining sodium chloride by this process is many centuries old.