nitrogen Grup

Hungarian national curriculum based material on Nitrogen group, onléy the first part (oxo-compounds missing)

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Chapter 4: Group V.A (15)
The elements of group V.A or Group 15 are:
Atomic Rel. Atomic Mass
symbol e­ configuration
Number
nitrogen N [He]2s22p3 7 14.007
phosphorus P [Ne]3s23p3 15 30.974
arsenic As [Ar]3d104s2 4p3 33 74.92
antimony Sb [Kr]4d105s2 5p3 51 121.75
[Xe]4f14 5d106s2
bismuth Bi 83 208.98
6p3
In this chapter only nitrogen and phophorus are considered. Information on other group V.A
elements is available at chapters about metals.
Nitrogen
Nitrogen is the seventh element in Mendeleev's periodic table. The relative atomic mass
suggests that nitrogen-14 is the common isotope. There is also another stable one with mass
numbers 15. Beside these naturally occurring isotopes there are 10 more. Out of these artificial
nitrogen atoms the atomic mass of 13 is worth mentioning.
Nitrogen takes the 5th place in the order of the mot abundant elements in the universe. In the
Earth it is the 13th most abundant making 78,09% of the atmosphere. It also gives three quarter
of the atmospheric mass. It was discovered in 1772 by D. Rutherford. Besides this elemental form,
nitrogen can also be found in compounds: such as nitrates or ammonia.
Elemental nitrogen is a diatomic gas. There are no other stable allotropes. Allotropy of nitrogen is
exotic field requiring outstanding circumstances (1,1 million atm and 2000K) but
giving the diamond-like structure of N4. The nitrogen structure existing under
sustainable circumstances is the following:
1. ábra http://www.globalwarmingart.com/wiki/File:Nitrogen_Molecule_Formula_png
From this structure the following properties derive
­ The molecule is non-polar as there is no electronegativity difference between two nitrogen
atoms (`brotherly fifty-fifty share'
­ Dispersal bonds maintain molecular lattice system
­ The bond energy (950 kJ/mol) is absolutely high due to the symmetrical triple covalent
bonds
­ Because of this structure the molecule has extremely low reactivity
­ It is called an inert gas for its low reactivity. It is often used as an inert atmosphere when
chemists need to work with substances that are sensitive to air (or more precisely oxygen).
­ It is odourless and colourless and it is in gaseous state at 25°C and standard pressure
­ The symmetrical non-polar nitrogen molecules are insoluble in water.
Chemistry of Nitrogen
DO NOT FORGET that nitrogen is the most inert diatomic gas at STP. Is it the most inert gas at
STP? (Name one substance!) Why?
1/12

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Chapter 4: Group V.A (15)
The most well-known reaction of nitrogen is its equilibrium reaction with hydrogen:
Nitrogen is combustible, however it requires high temperature (3000°C). The reaction can yield 2
different oxides. In complete combustion reaction nitrogen(IV) oxide forms. The incomplete
reaction gives nitrogen (II) oxide. There are further nitrogen oxides.
Complete combustion:
Incomplete combustion:
As the combustion of nitrogen costs too much of energy, nitrogen is first used for ammonia
synthesis then ammonia is burnt to produce nitrogen oxides.…read more

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Chapter 4: Group V.A (15)
the great extend, is insignificant compared to the overall mass of air. Annually around 56 million tones
of nitrogen and 700 thousands of argon are produced.
Based on N. N. Greenwwod - A. Earnshaw: The Chemistry of Elements
a) Using the given data determine the series of extraction for the six gases during the fractional
distillation of liquidified air.…read more

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Chapter 4: Group V.…read more

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Chapter 4: Group V.A (15)
Because of the lone pair ammonia may serve as a base in reactions. In its aqueous solution it is
often handled as ammonium hydroxide. It was proved that no such compound exists. (Without
aqueous medium the use of ammonium hydroxide is forbidden.) Ammonia is physically dissolved
in water (hydration) and a reaction takes place among ammonia and water molecules.…read more

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Chapter 4: Group V.A (15)
At the beginning of the 20th century there was a shortage of naturally occurring, nitrogen-rich
fertilisers, such as Chile saltpetre, which prompted the chemists to look for ways of combining the
nitrogen in the air with hydrogen to form ammonia, which is a convenient starting point in the
manufacture of fertilisers.…read more

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Chapter 4: Group V.A (15)
A temperature range of 400-500oC is a compromise designed to achieve an acceptable yield
of ammonia (10-20%) within an acceptable time period.
At 200oC and pressures above 750atm there is
an almost 100% conversion of reactants to the
ammonia product.
Since there are difficulties associated with
containing larger amounts of materials at this
high pressure, lower pressures of around 200
atm are used industrially.…read more

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Chapter 4: Group V.A (15)
Then the nitrogen passes through the food chain from plants to herbivores to carnivores.
When plants and animals eventually die, the nitrogen compounds are broken down giving ammonia
(ammonification). Some of the ammonia is taken up by the plants; some is dissolved in water or
held in the soil where bacteria convert it to nitrates (nitrification). Nitrates may be stored in
humus or leached from the soil and carried to lakes and streams.…read more

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Chapter 4: Group V.A (15)
(Source of information: mwrc.bio.cmich.edu/nitrogen.htm)
Oxo-compounds of Nitrogen
There are 6 different bicomponent compounds of nitrogen with oxygen. As there are 5
valence electrons, the oxidation state varies from +1 to +5. There are so-called binary oxides with
two nitrogen atoms with the same oxidation state or not. Most of the oxides are toxic and all of
them are prominent air pollutants. These compounds are related to each other by many chemical
reactions.
The odd-molecule-out is N2O with oxidation state +1.…read more

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Chapter 4: Group V.A (15)
Remember that nitrous acid is not a stable molecule, but the salts with nitrite anion are so. Its decomposition
reaction is a redox reaction:
HNO2= NO+ HNO3+ H2O
NITRIC ACID (HNO3)
Polarity:
Secondary bond and lattice system:
PHYSICAL PROPERTIES:
Odour:
Colour:
Physical state at STP:
The analytical cc.…read more

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