Manufacturers do not make nitrogen, but refine it through the fractional distillation of liquid air. The Earth's atmosphere is over 78 percent oxygen, which is one of the noble gases and does not easily form compounds with other elements.
Fractional distillation is a common method of separating a mixture of liquids. The process involves slowly heating the mixture while allowing the vapor produced to pass through a cooling tube to cool and condense it. As the mixture reaches the boiling point of one of its components, the temperature stops rising until that element evaporates and then starts to rise again. By knowing the boiling point of the chemical he wishes to isolate, the manufacturer collects the fraction containing that particular liquid. Nitrogen has a boiling point of minus 320.44 degrees Fahrenheit at standard atmospheric pressure, so liquefied air boils from the heat of the surrounding atmosphere.
Nitrogen has eight electrons in its outer valence shell and does not need bonding to other elements to form an electrically neutral compound. In addition to making the gas stable in its elemental form, this also makes nitrogen containing compounds relatively unstable. The instability of nitrogen compounds makes it a common chemical for use in explosives, yet plants fix nitrogen for their own use.