氨Ammonia

氮原子 sp³ 杂化，三个 N–H 键和一对孤电子呈四面体排布，H–N–H 键角 107°。孤对电子使氨成为路易斯碱和良好配体（如 [Cu(NH₃)₄]²⁺）。氨分子间存在氢键，沸点 −33 °C，易液化，液氨汽化时大量吸热，可作制冷剂。氨分子能发生“伞形翻转”，频率约 23.8 GHz，最早的微波激射器就利用了这一跃迁。

Nitrogen is sp³ hybridised, with three N–H bonds and one lone pair in a tetrahedral arrangement and an H–N–H angle of 107°. The lone pair makes ammonia a Lewis base and a good ligand, as in [Cu(NH₃)₄]²⁺. Hydrogen bonding gives a boiling point of −33 °C, so it liquefies easily and absorbs much heat on evaporating, making it a refrigerant. The molecule inverts like an umbrella at about 23.8 GHz, the transition used in the first maser.

古代从骆驼粪附近的“卤砂”（NH₄Cl）中得到氨，名称来自埃及阿蒙神庙（Ammon）。1774 年普里斯特利首次收集到氨气，1785 年贝托莱确定其组成为 NH₃。1913 年哈伯-博施法实现由空气中的氮工业合成氨。

In antiquity ammonia was obtained from sal ammoniac (NH₄Cl) found near camel dung; the name comes from the temple of Ammon in Egypt. Priestley first collected the gas in 1774, and Berthollet established its composition, NH₃, in 1785. In 1913 the Haber–Bosch process began synthesising it from atmospheric nitrogen.

约 80% 的氨用于化肥（尿素、硝酸铵、硫酸铵、液氨直施），其余用于奥斯特瓦尔德法制硝酸、合成纤维、炸药和制冷。氨对眼睛和呼吸道有强烈刺激性，空气中 15–28% 时遇火可爆炸。氨也被视为潜在的无碳燃料和氢载体。

About 80% of ammonia goes into fertilisers (urea, ammonium nitrate, ammonium sulfate and direct injection); the rest makes nitric acid by the Ostwald process, synthetic fibres, explosives and refrigerants. It strongly irritates the eyes and airways, and 15–28% in air can explode on ignition. Ammonia is also studied as a carbon-free fuel and hydrogen carrier.