Nitrogen is a chemical element that has the symbol
N, atomic number 7 and atomic mass 14.00674 u.
Elemental nitrogen is a colorless, odorless, tasteless, and mostly
inert diatomic gas at standard conditions, constituting 78.08% by
volume of Earth's atmosphere. The element nitrogen was discovered
as a separable component of air, by Scottish physician Daniel
Rutherford, in 1772.
Many industrially important compounds, such as ammonia, nitric
acid, organic nitrates (propellants and explosives), and cyanides,
contain nitrogen. The extremely strong bond in elemental nitrogen
dominates nitrogen chemistry, causing difficulty for both organisms
and industry in breaking the bond to convert the N2 into useful
compounds, but at the same time causing release of large amounts of
often useful energy when the compounds burn, explode, or decay back
into nitrogen gas.
Nitrogen occurs in all living organisms, and the nitrogen cycle
describes movement of the element from the air into the biosphere
and organic compounds, then back into the atmosphere. Synthetically
produced nitrates are key ingredients of industrial fertilizers,
and also key pollutants in causing the eutrophication of water
systems. Nitrogen is a constituent element of amino acids and thus
of proteins and nucleic acids (DNA and RNA). It resides in the
chemical structure of almost all neurotransmitters, and is a
defining component of alkaloids, biological molecules produced by
many organisms. The human body contains about 3% by weight of
nitrogen, a larger fraction than all elements save oxygen, carbon,
and hydrogen.
Physical properties
Nitrogen is a nonmetal, with an electronegativity of 3.04. It has
five electrons in its outer shell and is, therefore, trivalent in
most compounds. The triple bond in molecular nitrogen (N2) is one
of the strongest. The resulting difficulty of converting N2 into
other compounds, and the ease (and associated high energy release)
of converting nitrogen compounds into elemental N2, have dominated
the role of nitrogen in both nature and human economic
activities.
Occurrence and production
Nitrogen is the largest single constituent of the Earth's
atmosphere (78.082% by volume of dry air, 75.3% by weight in dry
air). It is created by fusion processes in stars, and is estimated
to be the seventh most abundant chemical element by mass in the
universe.
Molecular nitrogen and nitrogen compounds have been detected in
interstellar space by astronomers using the Far Ultraviolet
Spectroscopic Explorer. Molecular nitrogen is a major constituent
of the Saturnian moon Titan's thick atmosphere, and occurs in
slightly appreciable to trace amounts in other planetary
atmospheres.
Applications
Nitrogen gas is an industrial gas produced by the fractional
distillation of liquid air, or by mechanical means using gaseous
air (i.e., pressurized reverse osmosis membrane or Pressure swing
adsorption). Commercial nitrogen is often a byproduct of
air-processing for industrial concentration of oxygen for
steelmaking and other purposes. When supplied compressed in
cylinders it is often called OFN (oxygen-free nitrogen).
Some other applications include:
Nitrogenated beer
A further example of its versatility is its use as a preferred
alternative to carbon dioxide to pressurize kegs of some beers, in
particular, stouts and British ales, due to the smaller bubbles it
produces, which make the dispensed beer smoother and headier. A
modern application of a pressure sensitive nitrogen capsule known
commonly as a "widget" now allows nitrogen charged beers to be
packaged in cans and bottles.
Precautions
When inhaled at high partial pressures (more than about 4 bar,
encountered at depths below about 30 m in scuba diving), nitrogen
begins to act as an anesthetic agent. It can cause nitrogen
narcosis, a temporary semi-anesthetized state of mental impairment
similar to that caused by nitrous oxide.
Nitrogen also dissolves in the bloodstream and body fats. Rapid
decompression (in particular, in the case of divers ascending too
quickly, or astronauts decompressing too quickly from cabin
pressure to spacesuit pressure) can lead to a potentially fatal
condition called decompression sickness (formerly known as caisson
sickness or the bends), when nitrogen bubbles form in the
bloodstream, nerves, joints, and other sensitive or vital areas.
Other "inert" gases (those gases other than carbon dioxide and
oxygen) cause the same effects from bubbles composed of them, so
replacement of nitrogen in breathing gases may prevent nitrogen
narcosis, but does not prevent decompression sickness.
PERIODIC TABLE
Check out this interactive Periodic Table.
Check out this Nitrogen video. Prepared by The University of
Nottingham.