Nitrogen is an element found in plants, animals, air and other non-living compounds. About 78% of the atmosphere is made up of nitrogen gas. It is colorless, odorless and tasteless. Nitrogen (symbol N) is element number 7. Its atomic weight is 14.007 (14.008, O =16).
Nitrogen gas is difficult to dissolve in water and does not combine readily with most elements. It is very essential for both plant life, which uses nitrogen to grow, and animal life, which uses nitrogen in very complicated structures called proteins.
Nitrogen was first mentioned in writings by D. Rutherford in 1772. Later it was studied by Scheele and Lavoisier and at that time was called azote. The word nitrogen comes from the Greek word nitron or saltpeter, a common compound of nitrogen. Most of the supply of soluble nitrogen once came from saltpeter or potassium nitrate, KNO3.
Nitrogen turns to a liquid at a temperature of about —196 °C, the boiling point of nitrogen.
Nitrogen gas is quite inert and combines with other elements very slowly. The reason is that the atoms in the diatomic molecule of nitrogen, N2, have a very strong bond. However, when nitrogen does combine with other elements, it forms some of the most active compounds. For example, explosives such as nitroglycerin and trinitrotoluene, or TNT, are nitrogen compounds.
