All practice pages/Interatomic theory/Diatomics
The molecule
Two nitrogen atoms locked together by a triple bond so strong that the gas hardly reacts with anything, which is exactly why it is useful.
The triple bond makes N₂ one of the least reactive substances there is; it is used precisely because it does nothing. It does react with lithium at room temperature and with burning magnesium to make nitrides, with hydrogen under heat, pressure and an iron catalyst to make ammonia, and with oxygen at the temperature of a lightning bolt or a car engine to make nitrogen oxides. Bacteria in soil and in the roots of beans and clover manage the same trick at room temperature, which is where most natural nitrogen fertilizer comes from.
Air is cooled until it liquefies, then warmed slowly: nitrogen boils off at −196 °C, before oxygen at −183 °C, so it can be collected almost pure. Smaller amounts come from membranes and adsorbent beds that let nitrogen through and hold oxygen back.
About half of the nitrogen produced becomes ammonia, then fertilizer, explosives and plastics. The rest is used for being inert: blanketing food packages, fuel tanks and chemical reactors so nothing oxidizes, and as liquid nitrogen, a cheap coolant for freezing food, storing cells and cooling instruments. Aircraft and racing tires are filled with it.
Not toxic, but it gives no warning. A room filled with nitrogen has no smell, and a person passes out within a few breaths without ever feeling short of breath. Liquid nitrogen causes instant frostbite.