Sodium is a soft, silver-white metal. Extremely reactive chemically, it is one of the alkali metals in group Ia of the periodic table . It must be stored out of contact with air and water and should be handled carefully. Sodium combines directly with the halogens. Metallic sodium has limited use.
Sodium hydroxide is used wherever a cheap alkali is needed, for example, in making soap .
Substances containing sodium impart a characteristic yellow color to a flame. Because of its activity sodium is not found uncombined in nature. It occurs abundantly and widely distributed in its compounds, which are present in rocks and soil, in the oceans, in salt lakes, in mineral waters, and in deposits in various parts of the world. Sodium compounds are found in the tissues of plants and animals. Sodium is an essential element in the diet, but some people must limit the amount of sodium in their food for medical reasons.