Nitrogen

Nitrogen, a chemical element, symbolized by N, whose individual atoms comprise a nucleus of seven protons, i.e,., it has an atomic number, Z = 7, meaning the nucleus has a positive electrical charge designated 7 e, with e representing the unit elementary charge. Seven electrons in two surrounding cloud-like energy shells charge-balance the seven protons, rendering the atom electrically neutral. The element occupies the seventh position in the periodic table, in virtue of its atomic number. Its nucleus naturally contains either seven neutrons, the isotope designated ¹⁴N (natural abundance 99.632%), or eight neutrons, the isotope designated ¹⁵N (natural abundance 0.368%). ¹⁴N has an atomic mass (formerly called atomic weight) of 14.0030740052 u, where u is the unified atomic mass unit; ¹⁵N has an atomic mass of 15.0001088984 u. The averaged atomic mass (also known as standard atomic weight) is 14.0067 u.

Covalently bonded with itself in a triple bond (sharing three electrons), the nitrogen molecule, (N₂), makes up about 78% by volume of dry air. At the Earth's surface normal temperature and pressure N₂ exists as a gas with no taste, color or odor. 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, a generic designation 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.