While sodium is one of the most abundant elements in the crust of the Earth, About.com indicates it never exists in its elemental form. It is highly reactive and forms many compounds, including sodium chloride, or table salt. The most common form of sodium chloride on the Earth is halite, a mineral that miners remove from large mines. The rock salt from these mines remains from the evaporation of oceans.
According to Chemistry Explained, most people never see pure sodium metal, but they use compounds that contain sodium daily, including soaps, baking soda and drugs. Sodium compounds have a long history of use, and they are also easy to find. Sodium is instrumental in the formation of glass, which requires heating sodium carbonate and calcium chloride to form a clear substance. This process dates to ancient Egypt in 1370 B.C.
Until the early 1800s, chemists made no distinction between sodium and potassium. While they recognized these two forms of alkali came from mineral and vegetable sources, both potassium carbonate and sodium carbonate worked similarly in commercial processes. This discovery came only a few years after John Dalton explained matter as being composed of atoms and that samples of a compound are consistent.