编辑“︁氮”︁（章节）

===同素异形体===
{{main|氮的同素异形体}}
单原子氮是非常活泼的三[[自由基]]，有三个不成对电子。它极易和其它元素反应，生成氮化物。两个单原子氮之间的碰撞会产生激发态的N<sub>2</sub>分子，后者的能量之高甚至可以把稳定的[[二氧化碳]]和[[水]]撞成自由基。单原子氮可通过对0.1–2&nbsp;mmHg的氮气通电而成，并伴随着桃黄色的光。这种光直到结束通电后几分钟才会缓慢消失。{{sfn|Greenwood|Earnshaw|1997|pp=412–16}}

氮通常以[[氮气|N<sub>2</sub>]]形式存在。它是无色、无臭、无味的[[抗磁性]]气体，熔点−210&nbsp;°C，沸点−196&nbsp;°C。{{sfn|Greenwood|Earnshaw|1997|pp=412–16}}由于N<sub>2</sub>中含有又短（109.76&nbsp;pm）、键能又高（945.41&nbsp;kJ/mol），因此很强的氮氮[[三键]]，它并不活泼，但仍可和金属[[锂]]和某些[[过渡金属]]配合物反应。{{sfn|Greenwood|Earnshaw|1997|pp=412–16}}<ref>{{cite web | url=http://www.uigi.com/nitrogen.html | title=Universal Industrial Gases, Inc...Nitrogen N2 Properties, Uses, Applications - Gas and Liquid | access-date=2013-09-30 | archive-date=2013-09-28 | archive-url=https://web.archive.org/web/20130928194449/http://www.uigi.com/nitrogen.html | dead-url=no }}</ref>

氮还有可能形成[[低聚物]]和聚合物。它们如果真的被合成了，将会是能量密度极高的材料，可用作推进剂或炸药。<ref name="Lewars">{{cite book |title=Modeling Marvels: Computational Anticipation of Novel molecules |last=Lewars |first=Errol G. |year=2008 |publisher=[[Springer Science+Business Media]] |isbn=978-1-4020-6972-7 |doi=10.1007/978-1-4020-6973-4 |pages=141–63 }}</ref>在[[金刚石对顶砧]]产生的110万个[[大气压]]的高压和2000&nbsp;K的高温下，氮会聚合成由单键链接而成的晶体。它的结构与[[钻石]]相似，且都有极强的[[共价键]]，因此别名“氮钻石”。<ref>{{Cite news|url=http://www.physorg.com/news693.html|title=Polymeric nitrogen synthesized|publisher=physorg.com|date=5 August 2004|access-date=2009-06-22|archive-date=2012-01-24|archive-url=https://web.archive.org/web/20120124231419/http://www.physorg.com/news693.html|url-status=live}}</ref>

[[File:Mountainous Shoreline of Sputnik Planum (PIA20198).png|thumb|right|upright=1.1|[[冥王星]][[史波尼克高原]]（图片右下方）的{{le|固态氮|Solid nitrogen}}]]
在常压下，N<sub>2</sub>会在{{convert|77|K|C}}下[[液化]]，在{{convert|63|K|C}}下[[凝固]]成[[六方晶系]]的β相，<ref name="Gray">{{cite book|last=Gray|first=Theodore|title=The Elements: A Visual Exploration of Every Known Atom in the Universe|date=2009|publisher=Black Dog & Leventhal Publishers|location=New York|isbn=978-1-57912-814-2}}</ref>而继续降温到{{convert|35.4|K|C}}则会使N<sub>2</sub>变成[[立方晶系]]的α相。<ref name="schu">{{cite journal|last1=Schuch|first1=A. F.|last2=Mills|first2=R. L.|title=Crystal Structures of the Three Modifications of Nitrogen 14 and Nitrogen 15 at High Pressure|journal=The Journal of Chemical Physics|date=1970|volume=52|issue=12|pages=6000–08|doi=10.1063/1.1672899|bibcode=1970JChPh..52.6000S}}</ref>[[液氮]]和水一样是无色液体，但其密度（0.808&nbsp;g/mL）只有水的80.8%，是常用的[[制冷剂]]。<ref>{{Cite journal | last1 = Iancu | first1 = C. V. | last2 = Wright | first2 = E. R. | last3 = Heymann | first3 = J. B. | last4 = Jensen | first4 = G. J. | title = A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography | doi = 10.1016/j.jsb.2005.12.004 | journal = Journal of Structural Biology | volume = 153 | issue = 3 | pages = 231–40 | year = 2006 | pmid = 16427786}}</ref>{{le|固态氮|Solid nitrogen}}有多种晶体结构，是冥王星<ref>{{cite news|title=Flowing nitrogen ice glaciers seen on surface of Pluto after New Horizons flyby|url=http://www.abc.net.au/news/2015-07-25/flowing-nitrogen-ice-glaciers-seen-on-surface-of-pluto/6647636|newspaper=ABC News|access-date=6 October 2015|date=25 July 2015|archive-date=29 September 2015|archive-url=https://web.archive.org/web/20150929044226/http://www.abc.net.au/news/2015-07-25/flowing-nitrogen-ice-glaciers-seen-on-surface-of-pluto/6647636|url-status=live}}</ref>和[[海卫一]]<ref>{{cite encyclopedia|title = Encyclopedia of the Solar System "Triton"|last1 = McKinnon|first1 = William B.|last2 = Kirk|first2 = Randolph L.|publisher = [[Elsevier]]|date = 2014|editor1-first = Tilman|editor1-last = Spohn|editor2-first = Doris|editor2-last = Breuer|editor3-first = Torrence|editor3-last = Johnson|edition = 3rd|location = Amsterdam; Boston|isbn = 978-0-12-416034-7|pages = 861–82|url = https://books.google.com/books?id=0bEMAwAAQBAJ&pg=PA861|access-date = 2016-04-30|archive-date = 2016-09-03|archive-url = https://web.archive.org/web/20160903233037/https://books.google.com/books?id=0bEMAwAAQBAJ&pg=PA861|url-status = live}}</ref>表面的主要成分。即使在那边的低温下，这些固态氮仍具有挥发性，容易[[升华]]，形成氮气。这些氮气有的形成大气层，有的形成[[霜]]。在海卫一的极地冰盖，还会有氮气组成的[[间歇泉]]。<ref>{{cite web |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Triton |publisher=[[NASA]] |access-date=September 21, 2007 |title=Neptune: Moons: Triton |archive-url=https://web.archive.org/web/20111015074425/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Triton |archive-date=October 15, 2011 |url-status=dead }}</ref>

2025年6月，[[苏州大学]]校友，德国[[吉森大学]]博士生钱伟煜(Weiyu Qian)等人在[[Nature]]上发文,宣布发现了氮的新一种同素异形体：“六氮”(hexanitrogen) N₆分子<ref>{{Cite journal |last=Qian |first=Weiyu |last2=Mardyukov |first2=Artur |last3=Schreiner |first3=Peter R. |title=Preparation of a neutral nitrogen allotrope hexanitrogen C2h-N6 |url=https://www.nature.com/articles/s41586-025-09032-9 |journal=Nature |language=en |date=2025-06 |volume=642 |issue=8067 |doi=10.1038/s41586-025-09032-9 |issn=1476-4687 |pmc=12158757 |pmid=40500322 |access-date=2025-12-31}}</ref> 。该分子可以视为[[叠氮根]] N₃⁻的二聚单质状态，并且可以与[[拟卤素]]类比。