Giving s altpeter - this is how the word Nitrogenium is translated from Latin. This is the name of nitrogen - 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, it is distributed in the air shell of the Earth - the atmosphere. A variety of nitrogen compounds are found in the earth's crust and living organisms, and are widely used in industries, military affairs, agriculture and medicine.
Why nitrogen was called "suffocating" and "lifeless"
As historians of chemistry suggest, Henry Cavendish (1777) was the first to receive this simple substance. The scientist passed air over hot coals, using alkali to absorb the reaction products. As a result of the experiment, the researcher discovered a colorless, odorless gas that did not react with coal. Cavendish called it "suffocating air" for being unable to sustain breathing as well as burning.
A modern chemist would explain that oxygen reacted with carbon to form carbon dioxide. The remaining "suffocating" part of the air consisted mostly of N2 molecules. Cavendish and other scientists at that time did not yet know about this substance, although nitrogen and s altpeter compounds were then widely used in the economy. The scientist reported the unusual gas to his colleague, who conducted similar experiments, Joseph Priestley.
At the same time, Karl Scheele drew attention to an unknown constituent of the air, but failed to correctly explain its origin. Only Daniel Rutherford in 1772 realized that the “suffocating” “spoiled” gas present in the experiments was nitrogen. Which scientist should be considered his discoverer - historians of science are still arguing about this.
Fifteen years after Rutherford's experiments, the famous chemist Antoine Lavoisier suggested changing the term "spoiled" air, referring to nitrogen, to another - Nitrogenium. By that time, it was proved that this substance does not burn, does not support breathing. At the same time, the Russian name "nitrogen" appeared, which is interpreted in different ways. The term is most often said to mean "lifeless". Subsequent work refuted the widespread opinion about the properties of matter. Nitrogen compounds - proteins - are the most important macromolecules in the composition of living organisms. To build them, plants absorb the necessary elements of mineral nutrition from the soil - ions NO32- and NH4+.
Nitrogen is a chemical element
The periodic system (PS) helps to understand the structure of the atom and its properties. By the position of a chemical element in the periodic table, one can determinenuclear charge, number of protons and neutrons (mass number). It is necessary to pay attention to the value of atomic mass - this is one of the main characteristics of the element. The period number corresponds to the number of energy levels. In the short version of the periodic table, the group number corresponds to the number of electrons in the outer energy level. Let's summarize all the data in the general characteristics of nitrogen by its position in the periodic system:
- This is a non-metallic element, located in the upper right corner of the PS.
- Chemical sign: N.
- Order number: 7.
- Relative atomic mass: 14.0067.
- Volatile hydrogen compound formula: NH3 (ammonia).
- Produces the highest oxide N2O5, in which the nitrogen valency is V.
The structure of the nitrogen atom:
- Core charge: +7.
- Number of protons:7; number of neutrons: 7.
- Number of energy levels: 2.
- Total number of electrons: 7; electronic formula: 1s22s22p3.
The stable isotopes of element No. 7 have been studied in detail, their mass numbers are 14 and 15. The content of atoms of the lighter of them is 99.64%. There are also 7 protons in the nuclei of short-lived radioactive isotopes, and the number of neutrons varies greatly: 4, 5, 6, 9, 10.
Nitrogen in nature
The Earth's air shell contains molecules of a simple substance, the formula of which is N2. The content of gaseous nitrogen in the atmosphere is by volumeabout 78.1%. Inorganic compounds of this chemical element in the earth's crust are various ammonium s alts and nitrates (nitrates). Formulas of compounds and names of some of the most important substances:
- NH3, ammonia.
- NO2, nitrogen dioxide.
- NaNO3, sodium nitrate.
- (NH4)2SO4, ammonium sulfate.
Valence of nitrogen in the last two compounds - IV. Coal, soil, living organisms also contain bound N atoms. Nitrogen is an integral part of amino acid macromolecules, DNA and RNA nucleotides, hormones and hemoglobin. The total content of a chemical element in the human body reaches 2.5%.
Simple substance
Nitrogen in the form of diatomic molecules is the largest part of the atmospheric air by volume and mass. A substance whose formula is N2 has no smell, color or taste. This gas makes up more than 2/3 of the Earth's air envelope. In liquid form, nitrogen is a colorless substance resembling water. Boils at -195.8 °C. M (N2)=28 g/mol. The simple substance nitrogen is slightly lighter than oxygen, its density in air is close to 1.
Atoms in a molecule firmly bind 3 common electron pairs. The compound exhibits high chemical stability, which distinguishes it from oxygen and a number of other gaseous substances. In order for a nitrogen molecule to disintegrate into its constituent atoms, it is necessary to expend an energy of 942.9 kJ / mol. A bond of three pairs of electrons is very strong.break down when heated above 2000 °C.
Under normal conditions, the dissociation of molecules into atoms practically does not occur. The chemical inertness of nitrogen is also due to the complete absence of polarity in its molecules. They interact very weakly with each other, which is the reason for the gaseous state of matter at normal pressure and temperature close to room temperature. The low reactivity of molecular nitrogen finds application in various processes and devices where it is necessary to create an inert environment.
Dissociation of molecules N2 can occur under the influence of solar radiation in the upper atmosphere. Atomic nitrogen is formed, which under normal conditions reacts with some metals and non-metals (phosphorus, sulfur, arsenic). As a result, there is a synthesis of substances that are obtained indirectly under terrestrial conditions.
Nitrogen valency
The outer electron layer of an atom is formed by 2 s and 3 p electrons. These negative particles of nitrogen can give up when interacting with other elements, which corresponds to its reducing properties. By attaching the missing 3 electrons to the octet, the atom exhibits oxidizing abilities. The electronegativity of nitrogen is lower, its non-metallic properties are less pronounced than those of fluorine, oxygen and chlorine. When interacting with these chemical elements, nitrogen gives up electrons (is oxidized). Reduction to negative ions is accompanied by reactions with other nonmetals and metals.
Typical valency of nitrogen is III. In this casechemical bonds are formed due to the attraction of external p-electrons and the creation of common (bonding) pairs. Nitrogen is capable of forming a donor-acceptor bond due to its lone pair of electrons, as happens in the ammonium ion NH4+.
Laboratory and industrial production
One of the laboratory methods is based on the oxidizing properties of copper oxide. A nitrogen-hydrogen compound is used - ammonia NH3. This foul-smelling gas reacts with powdered black copper oxide. As a result of the reaction, nitrogen is released and metallic copper (red powder) appears. Drops of water, another product of the reaction, settle on the walls of the tube.
Another lab method that uses a combination of nitrogen with metals is azide, such as NaN3. It turns out a gas that does not need to be purified from impurities.
Ammonium nitrite is decomposed into nitrogen and water in the laboratory. In order for the reaction to start, heating is required, then the process proceeds with the release of heat (exothermic). Nitrogen is contaminated with impurities, so it is purified and dried.
Production of nitrogen in industry:
- fractional distillation of liquid air - a method that uses the physical properties of nitrogen and oxygen (different boiling points);
- chemical reaction of air with red-hot coal;
- adsorption gas separation.
Interaction with metals and hydrogen - oxidizing properties
Inertness of strong moleculesdoes not allow obtaining some nitrogen compounds by direct synthesis. To activate atoms, strong heating or irradiation of the substance is necessary. Nitrogen can react with lithium at room temperature, with magnesium, calcium and sodium the reaction occurs only when heated. The corresponding metal nitrides are formed.
The interaction of nitrogen with hydrogen occurs at high temperatures and pressures. This process also requires a catalyst. It turns out ammonia - one of the most important products of chemical synthesis. Nitrogen, as an oxidizing agent, exhibits three negative oxidation states in its compounds:
- −3 (ammonia and other hydrogen compounds of nitrogen are nitrides);
- −2 (hydrazine N2H4);
- −1 (hydroxylamine NH2OH).
The most important nitride - ammonia - is produced in large quantities in industry. The chemical inertness of nitrogen remained a big problem for a long time. S altpeter was its source of raw materials, but mineral reserves began to decline rapidly as production increased.
A great achievement of chemical science and practice was the creation of the ammonia method of nitrogen fixation on an industrial scale. Direct synthesis is carried out in special columns - a reversible process between nitrogen obtained from air and hydrogen. When creating optimal conditions that shift the equilibrium of this reaction towards the product, using a catalyst, the ammonia yield reaches 97%.
Interaction with oxygen - reducing properties
In order to start the reaction of nitrogen and oxygen, strong heating is necessary. An electric arc and a lightning discharge in the atmosphere have sufficient energy. The most important inorganic compounds in which nitrogen is in its positive oxidation states:
- +1 (nitric oxide (I) N2O);
- +2 (nitrogen monoxide NO);
- +3 (nitric oxide (III) N2O3; nitrous acid HNO2, its s alts are nitrites);
- +4 (nitrogen (IV) dioxide NO2);
- +5 (nitrogen pentoxide (V) N2O5, nitric acid HNO3, nitrates).
Meaning in nature
Plants absorb ammonium ions and nitrate anions from the soil, use for chemical reactions the synthesis of organic molecules, constantly going on in cells. Atmospheric nitrogen can be absorbed by nodule bacteria - microscopic creatures that form growths on the roots of legumes. As a result, this group of plants receives the necessary nutrient element, enriches the soil with it.
During tropical downpours, atmospheric nitrogen oxidation reactions occur. Oxides dissolve to form acids, these nitrogen compounds in water enter the soil. Due to the circulation of the element in nature, its reserves in the earth's crust and air are constantly replenished. Complex organic molecules containing nitrogen are decomposed by bacteria into inorganic components.
Practical use
The most important connectionsnitrogen for agriculture are highly soluble s alts. Plants assimilate urea, s altpeter (sodium, potassium, calcium), ammonium compounds (an aqueous solution of ammonia, chloride, sulfate, ammonium nitrate). nitrates. Parts of the plant organism are able to store macronutrients "for future use", which worsens the quality of products. An excess of nitrates in vegetables and fruits can cause poisoning in people, the growth of malignant neoplasms. In addition to agriculture, nitrogen compounds are used in other industries:
- to receive medicines;
- for the chemical synthesis of macromolecular compounds;
- in the production of explosives from trinitrotoluene (TNT);
- for the production of dyes.
NO oxide is used in surgery, the substance has an analgesic effect. The loss of sensations when inhaling this gas was noticed even by the first researchers of the chemical properties of nitrogen. This is how the trivial name "laughing gas" appeared.
Problem of nitrates in agricultural products
Nitric acid s alts - nitrates - contain a singly charged anion NO3-. Until now, the old name of this group of substances is used - s altpeter. Nitrates are used to fertilize fields, in greenhouses, orchards. They are applied in early spring before sowing, in summer - in the form of liquid dressings. The substances themselves do not pose a great danger to humans, butin the body, they turn into nitrites, then into nitrosamines. Nitrite ions NO2- are toxic particles, they cause the oxidation of ferrous iron in hemoglobin molecules into trivalent ions. In this state, the main substance of the blood of humans and animals is not able to carry oxygen and remove carbon dioxide from tissues.
What is the danger of nitrate contamination of food for human he alth:
- malignant tumors that occur when nitrates are converted to nitrosamines (carcinogens);
- development of ulcerative colitis,
- hypotension or hypertension;
- heart failure;
- blood clotting disorder
- liver, pancreas, diabetes development;
- development of kidney failure;
- anemia, impaired memory, attention, intelligence.
Simultaneous consumption of different foods with high doses of nitrates leads to acute poisoning. Sources can be plants, drinking water, prepared meat dishes. Soaking in clean water and cooking can reduce the nitrate content of foods. The researchers found that higher doses of hazardous compounds were found in immature and greenhouse plant products.
Phosphorus is an element of the nitrogen subgroup
Atoms of chemical elements that are in the same vertical column of the periodic system exhibit common properties. Phosphorus is located in the third period, belongs to the 15th group, like nitrogen. The structure of atomselements are similar, but there are differences in properties. Nitrogen and phosphorus exhibit a negative oxidation state and valency III in their compounds with metals and hydrogen.
Many reactions of phosphorus take place at ordinary temperatures, it is a chemically active element. It interacts with oxygen to form a higher oxide P2O5. An aqueous solution of this substance has the properties of an acid (metaphosphoric). When it is heated, orthophosphoric acid is obtained. It forms several types of s alts, many of which serve as mineral fertilizers, such as superphosphates. Compounds of nitrogen and phosphorus are an important part of the cycle of substances and energy on our planet, they are used in industrial, agricultural and other fields of activity.
