N2

N2 is the diatomic molecule consisting of two nitrogen atoms. It is the most abundant form of elemental nitrogen and accounts for about 78 percent of Earth's atmosphere. In nature, N2 is highly stable and relatively unreactive at ambient conditions, which contributes to its role as an inert background gas in many processes.

The bonding in N2 features a triple bond between the two nitrogen atoms, giving a short bond length of around 1.10 Å and a bond energy near 941 kJ/mol. The molecule is nonpolar and diamagnetic, reflecting equal sharing of electrons and no unpaired electrons. At room temperature, N2 is a colorless, odorless, and tasteless gas with a boiling point of −195.8 °C and a melting point near −210 °C, making it a liquid only at cryogenic temperatures.

Occurrence and production vary by context. In the atmosphere, N2 is the dominant gas but is relatively inert. Industrially, it is produced from the air by fractional distillation after liquefaction, or generated as a byproduct in various processes. It is commonly stored and transported as a compressed gas or as a liquid for cryogenic use.

Uses and applications are widespread. N2 provides an inert shielding atmosphere for chemical reactions, welding, and the preservation of sensitive materials. It is used for blanketing and purging in electronics and pharmaceuticals, in modified atmosphere packaging, and as a coolant in the form of liquid nitrogen for cryogenic applications.

Biologically and environmentally, N2 is a key reservoir in the nitrogen cycle. It is largely unavailable to living organisms until converted by nitrogen-fixing bacteria or industrial processes into ammonia or other bioavailable forms. Safety considerations center on asphyxiation in enclosed spaces, since N2 can displace oxygen.