ETYM New Lat., fromE. soda.
Soft, waxlike, silver-white, metallic element, symbol Na (from Latin natrium), atomic number 11, relative atomic mass 22.898. It is one of the alkali metals and has a very low density, being light enough to float on water. It is the sixth-most abundant element (the fourth-most abundant metal) in the Earth’s crust. Sodium is highly reactive, oxidizing rapidly when exposed to air and reacting violently with water. Its most familiar compound is sodium chloride (common salt), which occurs naturally in the oceans and in salt deposits left by dried-up ancient seas.
Other sodium compounds are of great industrial importance and thousands of tons are manufactured annually. Sodium functions with potassium on the cellular level to make possible neuronal transmission, and so it is an essential nutrient for animals. It was named in 1807 by Humphry Davy, because he isolated it from caustic soda (sodium hydroxide).
A silvery soft waxy metallic element of the alkali metal group; occurs abundantly in natural compounds (especially in salt water); burns with a yellow flame and reacts violently in water; occurs in sea water and in the mineral halite.