All about Nitrogen
Nitrogen with the symbol N is a gaseous element that makes up the
largest portion of the Earth's atmosphere. The atomic number of
nitrogen is 7. Nitrogen is in group 15 of the periodic table.
Nitrogen was isolated by the British doctor Daniel Rutherford in
1772 and recognized as an elemental gas by the French chemist Antoine
Lavoisier about 1776.
Nitrogen is a colourless, odourless, tasteless and a non-toxic
gas. It can be condensed into a colourless liquid, which can also
in turn be compressed into a colourless, crystalline solid. Nitrogen
exists in two natural isotopic forms and even four radioactive isotopes
have been artificially prepared. Nitrogen melts at -210.01°
C (-346.02° F), boils at -195.79° C (-320.42° F), and
has a density of 1.251 g/litre at 0° C (32° F) and 1 atmosphere
pressure. The atomic weight of nitrogen is 14.007. This is generally
considered as 14.
Nitrogen is obtained from the atmosphere by passing air over heated
copper or iron. The oxygen is removed from the air, leaving nitrogen
mixed with inert gases. Pure nitrogen is obtained by fractional
distillation of liquid air; because liquid nitrogen has a lower
boiling point than liquid oxygen, the nitrogen distills off first
and can be collected.
Nitrogen composes about four-fifths , 78per cent , by volume of
the atmosphere. Nitrogen is inert and serves as a diluter for oxygen
in burning and respiration processes. It is an important element
in plant nutrition. Many bacterias in the soil convert atmospheric
nitrogen into a form, such as nitrate which can be absorbed by plants
by a process called nitrogen fixation. Nitrogen in the form of protein
is an important constituent of animal tissue. The element occurs
in the combined state in minerals, of which saltpetre (KNO3) and
Chile saltpetre (NaNO3) are commercially important products.
Nitrogen combines with other elements only at very high temperatures
or pressures. It can even be converted to an active form by passing
through an electric discharge at low pressure. The nitrogen so produced
is very active. It combines with alkali metals to form azides; with
the vapour of zinc, mercury, cadmium, and arsenic to form nitrides;
and with many hydrocarbons to form hydrocyanic acid and cyanides
which are also known as nitriles. Activated nitrogen returns to
ordinary nitrogen in about one minute.
In the combined state nitrogen takes part in many reactions. It
forms so many compounds that a systematic scheme of compounds containing
nitrogen in place of oxygen was created by the American chemist
Edward Franklin. In compounds nitrogen exists in all the valence
states between -3 and +5. Ammonia, hydrazine and hydroxylamine represent
compounds in which the valence of nitrogen is -3, -2, and -1, respectively.
Oxides of nitrogen represent nitrogen in all the positive valence
Most of the nitrogen used in the chemical industry is obtained
by the fractional distillation of liquid air. It is used in the
synthesis ammonia. From ammonia a wide variety of important chemical
products are prepared, including fertilizers, nitric acid, urea,
hydrazine, and amines. In addition, an ammonia compound is used
in the preparation of nitrous oxide (N2O) which is a colourless
gas popularly known as laughing gas. Mixed with oxygen, nitrous
oxide is used as an anaesthetic for many types of surgery. It is
even used as a coolant.
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