Nitrogen in our atmosphere is a diatomic gas.
Nitrogen, or N2, is the most abundant gas in Earth's atmosphere. It's also an essential nutrient for life; the form found in the atmosphere, however, is relatively inert and thus difficult for plants and animals to use.
Significance
Nitrogen is an important component of amino acids -- the building blocks of proteins -- and nucleic acids like DNA and RNA. Consequently, all known forms of life need a source of nitrogen. Plants do not use nitrogen to make nitrogen gas; they use it to make the organic compounds they need for DNA, RNA and protein synthesis.
Function
Unfortunately, nitrogen's electron configuration is such that by itself it forms a diatomic molecule with a triple bond between the two nitrogen atoms. This structure is a very low-energy arrangement and thus extremely stable, because a considerable amount of energy input is required to break these bonds, so nitrogen gas is fairly nonreactive. For plants and animals like humans to use nitrogen, we must first convert nitrogen into another form we can use.
Effects
In the environment, nitrogen-fixing bacteria can convert nitrogen from the atmosphere first into ammonia and then into nitrates. Plants use the nitrates to meet their needs. To make fertilizer and sustain large-scale agriculture, humans have devised the Haber-Bosch process, a chemical reaction that converts nitrogen gas and hydrogen into ammonia -- albeit at a high cost in terms of the energy required to make the reaction happen.
