Nitrogen is one of the four main components of Earth's atmosphere.
Nitrogen is an element, the seventh element of the periodic table. In nature it's found primarily in its gaseous form as a diatomic molecule with the molecular formula N2. Since important organic molecules like DNA and proteins contain nitrogen, this element is vital for life as we know it on Earth. Nitrogen gas can be derived from several important sources.
Atmosphere
According to "Essential Environment," nitrogen constitutes 78 percent by mass of Earth's atmosphere. All atmospheric nitrogen is in the gaseous form, so the atmosphere is the most abundant source of nitrogen gas. Unfortunately, gaseous nitrogen is largely inert or nonreactive, so in its gaseous form it's unavailable to plants, animals and other lifeforms that need it. Certain soil bacteria fix atmospheric nitrogen so that other plants and animals can use it. Humans also convert atmospheric nitrogen gas to ammonia through the Haber-Bosch process, an industrial process that serves as an essential source of nitrogen for fertilizers and explosives.
Denitrifying Bacteria
After nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia, other soil bacteria called nitrifying bacteria convert it in turn to nitrate ions and compounds so that it's available for plants--and animals such as humans that depend on plants for food. Once the animals or plants die and decay, decomposers return the nitrogen to the nitrifying bacteria in the form of ammonium ions. Other bacteria called denitrifying bacteria can also convert nitrates in the soil back into gaseous nitrogen and return it to the atmosphere. Denitrifying bacteria are another source of nitrogen gas.
Decomposition Reactions
Certain ammonium salts decompose when heated to release nitrogen gas. Three compounds that undergo this type of reaction are ammonium dichromate, ammonium permanganate and ammonium nitrate. All four compounds can act as explosives, especially ammonium nitrate, so it's not advisable to perform this kind of experiment at home.
