Nitrogen

Nitrogen is a chemical element with atomic number Z = 7 and chemical symbol N. The element takes the seventh position in the periodic table, because its nucleus contains seven protons, so that the element has positive nuclear charge 7e, where e is the elementary charge. The most common, naturally occurring, isotope (abundance 99.632%) is ¹⁴N; it has atomic mass (formerly called atomic weight) 14.0030740052 u, where u is the unified atomic mass unit. One other isotope occurs in nature: ¹⁵N (0.368% abundance) with atomic mass 15.0001088984 u. The averaged atomic mass (also known as standard atomic weight) is 14.0067 u.

The nitrogen molecule (N₂) makes up about 78% by volume of dry air. At normal temperature and pressure it is a tasteless, odorless, and colorless gas. The nitrogen molecule is chemically rather inert, it does not burn, does not support combustion and is only slightly soluble in water. At high temperature it combines with oxygen to form NO_x. This is a generic term for the class of nitrogen oxides containing NO, NO₂, N₂O, N₂O₃, N₂O₄, N₂O₅, and NO₃. Several of these oxides are formed during operation of combustion engines.

Nitrogen is important for living organisms because it is an important element of amino acids. Synthetic fertilizers contain nitrogen obtained from air by the Haber-Bosch process, a so-called nitrogen fixation process.