dinitrogen

Dinitrogen, or molecular nitrogen, is the diatomic molecule with the formula N2. It consists of two identical nitrogen atoms linked by a very strong triple bond, making it one of the most stable and inert molecules under ordinary conditions. Its bond length is about 1.097 angstroms and its bond energy is around 941 kilojoules per mole. In its neutral gaseous state at room temperature, N2 is colorless, odorless, and nonpolar.

Atmosphere and reactivity: About 78 percent of Earth's atmosphere by volume is N2. Despite its abundance, N2 is relatively unreactive because of the strong N≡N bond, so it resists most chemical reactions at ambient conditions. To become biologically or chemically usable, nitrogen must be fixed into reactive forms such as ammonia or nitrate. This fixation occurs biologically through certain bacteria and cyanobacteria, by lightning, or industrially via the Haber-Bosch process.

Industrial and biological roles: The Haber-Bosch process converts N2 and hydrogen into ammonia under high pressure and temperature with catalysts, supplying a key precursor for fertilizers and numerous nitrogenous chemicals. In nature, nitrogen fixation enables the incorporation of nitrogen into amino acids, nucleotides, and other biomolecules, sustaining living systems.

Applications and safety: N2 is widely used as an inert shielding gas in welding and chemical synthesis, and for cryogenic cooling when liquefied as liquid nitrogen. It is non-toxic but can act as an asphyxiant in enclosed spaces by displacing oxygen.