|Name: nitrogen||Group number: 15|
|Symbol: N||Group name: Pnictogen|
|Atomic number: 7||Period number: 2|
|Atomic weight: 14.0067 (2) g r||Block: p-block|
|CAS Registry ID: 7727-37-9||Voice: |
|Standard state: gas at 298 K||Colour: colourless|
|Classification: Non-metallic||Availability: |
Image adapted with permission from Prof James Marshall"s (U. North Texas, USA) Walking Tour of the elements CD.
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.
[QuickTime, 0.7mb download]
[MPEG, 1.9mb download]
To play the movies, you need QuickTime for MacOS or Windows installed, or some other MPEG movie viewer.
|The picture above shows the result of touching nitrogen triiodide (NI3)! Nitrogen triiodide is percussion sensitive. Do not attempt this reaction unless are a professionally qualified chemist and you have carried out a legally satisfactory hazard assessment. Nitrogen triiodide is dangerous! Select a movie icon to see the result of touching nitrogen triiodide.|
Nearing Zero cartoon included by kind permission of Nick Kim.
IsolationHere is a brief summary of the isolation of nitrogen.
There is never any need ot make nitrogen in the laboratory as it is readily available commercially or through in-house air liquefaction plants. However the decomposition of sodium azide is one route to N2 and decomposition is ammonium dichromate is another. Both reactions must only be carried out under controlled conditions by a professional.
NaN3 (300°C) 2Na + 3N2
(NH4)2Cr2O7 N2 + Cr2O3 + 4H2O
Nitrogen is made on massive scale by liquefaction of air and fractional distillation of the resulting liquid air to separate out oxygen and other gases. Very high purity nitrogen is available by this route.