born is nitrate - as translated from the Latin word Nitrogenium.This name oxide - a chemical element with atomic number 7, heading the 15th group in the long version of the periodic table.In the form of a simple substance distributed in the composition of the air shell of the Earth - atmosphere.Various nitrogen compounds found in the earth's crust and living organisms are widely used in industries, military, agriculture and medicine.
Why nitrogen called "choking" and "lifeless»
As suggested by historians of chemistry, has received the first is a simple matter of Henry Cavendish (1777).Scientific pass air over hot coals, to absorb the reaction products using alkali.As a result of the experience of the researcher discovered the colorless, odorless gas, unreacted coal.Cavendish named it "suffocating air" for the inability to maintain breathing and combustion.
modern chemist would explain that oxygen reacted with carbon formed carbon dioxide.The rest of "stifling" of the air consisted mostly of molecules N2.Cavendish and other scientists at the time of the substance did not know, although the compounds of nitrogen and then nitrate is widely used in the economy.The scientist told about the unusual gas to a colleague to conduct similar experiments - Joseph Priestley.
Simultaneously Karl Scheele drew attention to the unknown integral part of the air, but failed to properly explain its origin.Only Daniel Rutherford in 1772 realized that the present experiments "suffocating" "spoiled" gas - nitrogen.What the scientists consider it a pioneer - this is still debate historians of science.
15 years after Rutherford's experiments, the famous chemist Antoine Lavoisier proposed to replace the term "spoiled" air refers to nitrogen, on the other - Nitrogenium.By the time it has been proven that this substance is not illuminated, does not support breathing.Then there were the Russian name "nitrogen" is interpreted in different ways.Most often, they say that the term means "dead."Subsequent studies have refuted the popular belief about the properties of substances.Nitrogen compounds - proteins - the major macromolecules composed of living organisms.In order to construct plants absorb from the soil necessary elements of mineral nutrition - NO32- ions and NH4 +.
Nitrogen - a chemical element
understand the atomic structure and properties makes periodic system (PS).The position of the chemical element in the periodic table can determine the charge of the nucleus, the number of protons and neutrons (mass number).It is necessary to draw attention to the value of the atomic mass - is one of the main characteristics of the element.Number period corresponds to the number of energy levels.The short version of the periodic table group number corresponds to the number of electrons in the outer energaticheskom level.Summarize all the data in the general characteristics of nitrogen by its position in the periodic system:
- This is a non-metallic element is at the top right of the SS.
- chemical symbol: N.
- Number: 7.
- Relative atomic mass: 14.0067.
- Formula volatile hydrogen compounds: NH3 (ammonia).
- Forms highest oxide N2O5, which is equal to the valence of nitrogen V.
structure of nitrogen:
- charge of the nucleus +7.
- number of protons: 7;the number of neutrons: 7.
- number of energy levels: 2.
- total number of electrons: 7;e formula: 1s22s22p3.
stable isotopes studied in detail item number 7, and their mass numbers - 14 and 15. The content of the atoms easier ones is 99.64%.The nuclei are short-lived radioactive isotope as 7 protons and neutrons number varies greatly: 4, 5, 6, 9, 10.
Nitrogen
naturally a part of the air envelope Earth present molecules of the simple substance, whose formula - N2.The content of nitrogen gas in the atmosphere is about 78.1 volume%.Inorganic compounds of the chemical element in the earth's crust - various salts and ammonium nitrate (saltpeter).The formulas of the compounds and the names of some of the most important substances:
- NH3, ammonia.
- NO2, nitrogen dioxide.
- NaNO3, sodium nitrate.
- (NH4) 2SO4, ammonium sulfate.
valence of nitrogen compounds in the last two - IV.Coal, soil organisms also contain N atoms in bound form.Nitrogen is a component of macromolecules of amino acids, nucleotides, DNA and RNA, hormones and hemoglobin.The total content of chemical elements in the human body up to 2.5%.
simple substance
Nitrogen in the form of diatomic molecules - the largest by volume and weight of the air atmosphere.Substance, whose formula is N2, odorless, colorless and tasteless.This gas is more than 2/3 of the Earth's air bag.The liquid nitrogen is a colorless substance, resembling water.Boils at -195.8 ° C.M (N2) = 28 g / mol.Simple stuff a little easier nitrogen oxygen, the density of the air close to 1.
atoms in the molecule is firmly linked 3 shared electron pairs.The compound exhibits a high chemical resistance, which distinguishes it from oxygen and other gases.In order to split the nitrogen molecule into its constituent atoms necessary to spend energy 942.9 kJ / mol.Communication of the three pairs of electrons is very strong, begins to break down when heated above 2000 ° C.
Under normal conditions, the dissociation of molecules into atoms practically does not occur.Chemical inertness is also caused by nitrogen complete absence of polarity in its molecule.They interact very weakly with each other than due to a gaseous state of matter at normal pressure and at a temperature close to room temperature.Low reactivity molecular nitrogen is used for various processes and devices where it is necessary to create an inert environment.
dissociation of N2 molecules can occur under the influence of solar radiation in the upper atmosphere.Atomic nitrogen is formed, which under normal conditions reacts with certain metals and non-metals (phosphorus, sulfur, arsenic).The result is the synthesis of substances that in terrestrial conditions, the indirect way.
Valence nitrogen
outer electron shell of the atom form a 2 s, and 3 p, electron.These negative nitrogen can give particles when interacting with other elements that correspond to its reducing properties.Adding to the missing octet 3 electrons, atoms exhibit oxidative ability.Electronegativity nitrogen below its metallic properties are less pronounced than that of fluorine, oxygen and chlorine.The interaction of these chemical elements nitrogen loses electrons (oxidation).Reduction to negative ions followed by reaction with other metals and non-metals.
typical valence of the nitrogen - III.In this case the chemical bond formed by the attraction of external p-electrons and create a common (binding) pairs.Nitrogen is capable of forming a donor-acceptor bond by its lone pair of electrons, as is the ammonium ion, NH4 +.
obtained in the laboratory and industry
One laboratory method is based on oxidation properties of copper oxide.A connection nitrogen and hydrogen - ammonia NH3.This unpleasant smelling gas vzaimoddeystvuet with powdered copper oxide black.The resulting reaction produces nitrogen and appears metallic copper (red powder).Deposited on the tube walls waterdrops - another reaction product.
Another laboratory method that uses a nitrogen compound - metal azide, for example NaN3.Get gas, which does not need to be cleaned of impurities.
The laboratory carried out the decomposition of ammonium nitrite to nitrogen and water.To start the reaction, heating is required, then the process proceeds with evolution of heat (exothermic).Nitrogen is contaminated with impurities so it was purified and dried.
Preparation nitrogen industry:
- fractional distillation of liquid air - a method, which uses the physical properties of nitrogen and oxygen (different boiling point);
- chemical reaction of air with a hot coal;
- adsorptive gas separation.
interaction with metals and hydrogen - oxidizing properties
Inertia strong molecules can not produce some nitrogen compounds by direct synthesis.To activate the atoms need strong heating or irradiation of the substance.Nitrogen can react with lithium at room temperature, with magnesium, calcium and sodium, the reaction proceeds only by heating.Formed nitrides of the respective metals.
reaction of nitrogen and hydrogen occurs at high temperature and pressure.Also this process requires the catalyst.It turns ammonia - one of the most important products of chemical synthesis.Nitrogen as an oxidizer in their compounds exhibit negative three oxidation states:
- -3 (hydrogen, ammonia and other nitrogen compounds - nitrides);
- -2 (Hydrazine N2H4);
- -1 (hydroxylamine NH2OH).
most important nitride - ammonia - in large quantities produced in the industry.A big problem for a long time remained the chemical inertness of nitrogen.His raw material sources were ammonium nitrate, but stocks of minerals began to decline rapidly with the growth of production.
great achievement of chemical science and practice was the creation of ammonia nitrogen fixation technique on an industrial scale.In special columns is by direct synthesis - a reversible process between the nitrogen obtained from the air and hydrogen.When creating optimal conditions, this shifts the equilibrium reaction toward the product yield of ammonia using a catalyst reaches 97%.
reaction with oxygen - reducing properties
In order to initiate the reaction of nitrogen and oxygen, need strong heating.Enough energy to have an electric arc and a lightning discharge into the atmosphere.Major inorganic compound in which the nitrogen is in its positive oxidation states: +1
- (nitrogen oxide (I) N2O);
- +2 (nitrogen monoxide, NO);
- +3 (nitrogen oxide (III) N2O3, nitrous acid, HNO2, Nitrite salts thereof);
- +4 (nitrogen dioxide (IV) NO2);
- +5 (nitrogen pentoxide (V) N2O5, HNO3 nitric acid, nitrates).
value in nature
Plants absorb ammonium ions and nitrate anions from the soil, is used for the synthesis of chemical reactions of organic molecules in cells are constantly traveling.Atmospheric nitrogen can assimilate nodule bacteria - microscopic creatures that form nodules on the roots of legumes.As a result, this group of plants gets a necessary element of power, enriches the soil them.
during tropical storms occur oxidation of atmospheric nitrogen.The oxides are dissolved to form acids, these nitrogen compounds in the water coming into the soil.Thanks cycle of elements in nature are constantly replenished its reserves in the earth's crust, the air.Complex organic molecules containing nitrogen in its composition, bacteria decompose into inorganic constituents.
Practical use
most important nitrogen compounds for agriculture - a highly soluble salt.Absorbed by plants urea nitrate (sodium, potassium, calcium), ammonium compounds (ammonia water, chloride, sulfate, ammonium nitrate).
inert properties of nitrogen, the inability of plants to absorb it from the air each year lead to the need to make high doses of nitrates.Parts of the plant organism are able to store food macro element "in store", which degrades the quality of products.Excess nitrates in vegetables and fruits can cause poisoning in humans, growth of malignant neoplasms.Besides agriculture, the nitrogen compounds are used in other industries:
- for medicines;
- for the chemical synthesis of high-molecular compounds;
- in the manufacture of explosives trinitrotoluene (TNT);
- for the production of dyes.
oxide NO is used in surgery, the substance has analgesic effect.Loss of sensation in the inhalation of this gas even noticed the first explorers chemical properties of nitrogen.So there was a common name "laughing gas."
problem of nitrates in agricultural products
The salts of nitric acid - nitrates - found singly charged anion NO3-.Until now, used the old name of this group of substances - ammonium nitrate.Nitrates are used to fertilize the fields, in greenhouses, gardens.Bring them in early spring before planting, in the summer - in the form of liquid feedings.By themselves, the substance does not represent a great danger for humans, but in the body they are converted into nitrite and then into nitrosamines.Nitrite ion NO2- - toxic particles, they cause the oxidation of ferrous iron in the hemoglobin molecules in the trivalent ions.In this state, the main ingredient of human blood and animals are not able to carry oxygen and remove carbon dioxide from the tissues.
The dangerous nitrate contamination of food for human health:
- malignant tumors that arise in the conversion of nitrates into nitrosamines (carcinogens);
- development of ulcerative colitis,
- hypotension or hypertension;
- heart failure;
- bleeding disorders
- lesions of the liver, the pancreas, the development of diabetes;
- development of renal failure;
- anemia, impaired memory, attention and intelligence.
simultaneous use of different products with large doses of nitrates leads to acute poisoning.The sources can be plants, bottled water, ready-made meat dishes.Soaking in pure water and cooked can be reduced nutritional content of nitrates.The researchers found that higher doses of dangerous compounds observed in immature and greenhouse vegetable production.
Phosphorus - element of the subgroup
nitrogen atoms of chemical elements that are in a single vertical column of the periodic system, showing the general properties.Phosphorus is in the third period, it refers to a group of 15, as well as nitrogen.The structure of the atoms of elements similar but there are differences in the properties.Nitrogen and phosphorus exhibit negative valence and oxidation state III in their compounds with metals and hydrogen.
Many reactions are phosphorus at ordinary temperatures, a chemically active element.Reacts with oxygen to form an oxide of higher P2O5.An aqueous solution of this material possesses acid properties (metaphosphoric).While heating orthophosphoric acid is obtained.It defines a plurality of types of salts, many of which are chemical fertilizers, for example superphosphates.Nitrogen and phosphorus compounds form an important part of the cycle of matter and energy on the planet, are used in industrial, agricultural and other spheres.
