氮(nitrogen)
气态化学元素，化学符号N，原子序数7。无色、无臭、无味的气体，占地球大气的78%，也是所有生物体的组成部分。它是最稳定的双原子分子N2，可用来产生惰性的气体氛围，或用於稀释气体。商业上通过液化空气的蒸馏来生产氮气。自然界通过土壤里的微生物可达成固定氮作用，而在工业上则利用哈伯－博施法将它转化成可溶於水的化合物（包括氨和硝酸盐）。氨是其他氮化合物（尤其是硝酸盐和亚硝酸盐）的起始物质，这些化合物主要用於农业肥料和炸药。氮能生成几种氧化物：一氧化二氮；氧化氮（NO），最近发现它在生理过程中起关键作用；二氧化氮，以及其他形式（包括N2O3和N2O5），它们会造成空气污染（尤其在日光照射下），故而臭名昭彰。其他的化合物包括氮化物，是由氮和金属生成的异常坚硬的材料；氰化物；叠氮化物，用作引爆剂和雷管；还有数千种含氮的有机化合物，以功能团或者线性或环状结构（参阅heterocyclic compound）的形式存在。
English version：
nitrogen
Gaseous chemical element, chemical symbol N, atomic number 7. A colorless, odorless, tasteless gas, it makes up 78% of the earth's atmosphere and is a constituent of all living matter. As the almost inert diatomic molecule N2, it is useful as an inert atmosphere or to dilute other gases. Nitrogen is commercially produced by distillation of liquefied air. Nitrogen fixation, achieved naturally by soil microbes and industrially by the Haber-Bosch process, converts it to water-soluble compounds (including ammonia and nitrates). Ammonia is the starting material for most other nitrogen compounds (especially nitrates and nitrites), whose main uses are in agricultural fertilizers and explosives. Nitrogen forms several oxides: nitrous oxide; nitric oxide (NO), recently found to play key roles in physiology; and nitrogen dioxide (NO2) and other forms (including N2O3 and N2O5) notorious for causing air pollution, especially when acted on by sunlight. Other compounds include the nitrides, exceptionally hard materials made from nitrogen and a metal; cyanides; azides, used in detonators and percussion caps; and thousands of organic compounds containing nitrogen in functional groups or in a linear or ring structure (see heterocyclic compound). See also nitrogen cycle.