Nitrogen

Preparation: Nitrogen, being the principal component of air (78% by volume), is obtained industrially on a large scale by the fractional distillation of liquefied air (nitrogen, boiling at 77 K, distils off before oxygen, which boils at 90 K). In the laboratory, pure nitrogen gas can be generated by the controlled thermal decomposition of sodium azide at about 575 K: 2NaN3 -> 2Na + 3N2. It can also be produced by oxidising ammonia with bromine water: 8NH3 + 3Br2 -> 6NH4Br + N2.

Properties: Nitrogen gas is chemically rather inert at room temperature. Naturally occurring (terrestrial) nitrogen is a mixture of about 99.6% nitrogen-14 and 0.4% nitrogen-15, the latter isotope being useful as an isotopic label in mechanistic and biochemical studies. Nitrogen's inertness is largely attributable to the very high bond dissociation energy of the N≡N triple bond (about 946 kJ/mol, i.e. 225 kcal/mol) — interestingly, despite this strong triple bond, N2 is markedly less reactive than other iso-electronic triply bonded species such as -C≡C-, C≡O and the cyanide/isocyanide groups (X-C≡N, X-N≡C), because those species can act as electron-pair donors through non-bonding or π electron density in a way that dinitrogen, lacking an easily accessible lone pair, largely cannot; nonetheless dinitrogen can act as a weak donor ligand towards some transition metals (M<-N≡N), somewhat like carbon monoxide, though to a much smaller extent. …