Sodium has an atomic number of 11 and a mass of about 23g. It is a silvery white-metallic element classified under the alkali metals. Sodium has been known since early times and was used by the people of Mesopotamia and Egypt to make glasses. Sodium is the sixth most common element found on the earth. It is usually not found in nature but more often in compounds such as salt (NaCl). Sodium conducts heat and electricity easily.