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7. NitrogenName: Nitrogen
Nitrogen is a Group 15 element. Nitrogen makes up about 78% of the atmosphere by volume but the atmosphere of Mars contains less than 3% nitrogen. The element seemed so inert that Lavoisier named it azote, meaning "without life". However, its compounds are vital components of foods, fertilizers, and explosives. Nitrogen gas is colourless, odourless, and generally inert. As a liquid it is also colourless and odourless. When nitrogen is heated, it combines directly with magnesium, lithium, or calcium. When mixed with oxygen and subjected to electric sparks, it forms nitric oxide (NO) and then the dioxide (NO2). When heated under pressure with hydrogen in the presence of a suitable catalyst , ammonia forms (Haber process). Nitrogen is "fixed" from the atmosphere by bacteria in the roots of certain plants such as clover. Hence the usefulness of clover in crop rotation. Nitrogen (Latin nitrum, Greek Nitron meaning "native soda", "genes", "forming") is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or phlogisticated air. That there was a fraction of air that did not support combustion was well known to the late 18th century chemist. Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or dephlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as azote, which stands for without life. Compounds of nitrogen were known in the Middle Ages. The alchemists knew nitric acid as aqua fortis. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold. Nitrogen is also used in filling automotive tires due to its relatively flat line of thermal expansion. Nitrate fertilizer washoff is a major source of ground water and river pollution. Cyano (-CN) containing compounds form extremely poisonous salts and are deadly to many animals and all mammals. Quick links
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