Nitrogenium-producing saltpeter - this is how the word Nitrogenium is translated from Latin. This is the name of nitrogen - a chemical element with atomic number 7, which leads the 15th group in a long version of the periodic table. In the form of a simple substance, it is common in the composition of the air shell of the Earth - the atmosphere. A variety of nitrogen compounds are found in the earth's crust and living organisms, are widely used in industries, military affairs, agriculture and medicine.
Why nitrogen was called "suffocating" and "lifeless"
As historians of chemistry suggest, the first to receive this simple substance was Henry Cavendish (1777). The scientist let air over hot coals, used 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 his inability to maintain breathing, as well as burning.
A modern chemist would explain that oxygen reacted with coal, carbon dioxide was formed. The remaining "suffocating" part of the air consisted mostly of N 2 molecules. Cavendish and other scientists at that time did not yet know about this substance, although nitrogen and nitrate compounds were then widely used on the farm. The scientist reported an unusual gas to his colleague who conducted similar experiments, Joseph Priestley.
At the same time, Karl Scheele drew attention to an unknown component of the air, but failed to correctly explain its origin. Only in 1772 did Daniel Rutherford realize that the “suffocating” “spoiled” gas present in the experiments was nitrogen. What kind of scientist to consider him the discoverer - the historians of science are still arguing about this.
Fifteen years after Rutherford’s experiments, the famous chemist Antoine Lavoisier proposed changing the term “spoiled” air related to nitrogen to Nitrogenium. By that time, it was proved that this substance does not burn, does not support breathing. Then the Russian name “nitrogen” appeared, which is interpreted differently. Most often they say that the term means "lifeless." Subsequent work refuted the widespread belief about the properties of matter. Nitrogen compounds - proteins - are the most important macromolecules in living organisms. To build them, plants absorb from the soil the necessary elements of mineral nutrition - NO 3 2- and NH 4+ ions.
Nitrogen - a chemical element
The periodic system (PS) helps to understand the structure of an atom and its properties. By the position of the chemical element in the periodic table, you can determine the nuclear charge, the 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 number of the period corresponds to the number of energy levels. In a short version of the periodic table, the group number corresponds to the number of electrons at the external energy level. Let us summarize all the data in the general characteristic 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.
- Sequence number: 7.
- Relative atomic mass: 14.0067.
- Formula for the volatile hydrogen compound: NH 3 (ammonia).
- Forms the highest oxide N 2 O 5 in which the valency of nitrogen 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: 1s 2 2s 2 2p 3 .
The stable isotopes of element No. 7 were 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 envelope contains molecules of a simple substance, the formula of which is N 2 . The nitrogen gas content in the atmosphere is about 78.1% by volume. Inorganic compounds of this chemical element in the earth's crust are various ammonium salts and nitrates (nitrate). Formulas of compounds and names of some of the most important substances:
- NH 3, ammonia.
- NO 2, nitrogen dioxide.
- NaNO 3, sodium nitrate.
- (NH 4 ) 2 SO 4, ammonium sulfate.
The valency of nitrogen in the last two compounds is IV. Coal, soil, living organisms also contain N atoms in bound form. Nitrogen is an integral part of the macromolecules of amino acids, nucleotides of DNA and RNA, 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 volume and mass of air in the atmosphere. The substance whose formula is N 2 does not have a 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. It boils at a temperature of –195.8 ° C. M (N 2 ) = 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 the nitrogen molecule to decay into its constituent atoms, it is necessary to expend energy of 942.9 kJ / mol. The bond of 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. 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 due to the gaseous state of the substance at normal pressure and temperature close to room temperature. The low chemical activity of molecular nitrogen is used in various processes and devices where it is necessary to create an inert environment.
Dissociation of N 2 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). As a result, there is a synthesis of substances that are obtained indirectly in terrestrial conditions.
Valence of nitrogen
The outer electron layer of an atom is formed by 2 s and 3 p of an electron. Nitrogen can give away these negative particles when interacting with other elements, which corresponds to its reducing properties. By attaching 3 electrons that are missing up to an octet, the atom exhibits oxidative abilities. The electronegativity of nitrogen is lower, its nonmetallic properties are less pronounced than that of fluorine, oxygen and chlorine. When interacting with these chemical elements, nitrogen gives off electrons (oxidizes). Reduction to negative ions is accompanied by reactions with other non-metals and metals.
Typical nitrogen valency is III. In this case, chemical bonds are formed due to the attraction of external p-electrons and the creation of common (binding) pairs. Nitrogen is capable of forming a donor-acceptor bond due to its lone pair of electrons, as occurs in the ammonium ion NH 4+ .
Obtaining in the laboratory and industry
One of the laboratory methods is based on the oxidizing properties of copper oxide. A compound of nitrogen with hydrogen is used - ammonia NH 3 . This foul-smelling gas interacts with powdered black copper oxide. As a result of the reaction, nitrogen is released and metallic copper (red powder) appears. Drops of water, another reaction product, settle on the walls of the tube.
Another laboratory method that uses a compound of nitrogen with metals is azide, for example NaN 3 . It turns out a gas that does not need to be cleaned of impurities.
In the laboratory, ammonium nitrite is decomposed into nitrogen and water. In order for the reaction to begin, heating is required, then the process proceeds with the release of heat (exothermic). Nitrogen is contaminated with impurities, so it is cleaned and drained.
Nitrogen production in industry:
- fractional distillation of liquid air - a method in which the physical properties of nitrogen and oxygen are used (different boiling points);
- chemical reaction of air with hot coal;
- adsorption gas separation.
Interaction with Metals and Hydrogen - Oxidizing Properties
The inertness of strong molecules does not allow the production of certain nitrogen compounds by direct synthesis. To activate atoms, strong heating or radiation of the substance is necessary. Nitrogen can react with lithium at room temperature, with magnesium, calcium and sodium, the reaction proceeds only when heated. The nitrides of the corresponding metals are formed.
The interaction of nitrogen with hydrogen occurs at high temperatures and pressures. A catalyst is also required for this process. 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 nitrogen compounds - nitrides);
- −2 (hydrazine N 2 H 4 );
- −1 (hydroxylamine NH 2 OH).
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. Nitrate was its raw material source, but mineral reserves began to decline rapidly with increasing production.
A great achievement in chemical science and practice was the creation of an ammonia method of nitrogen binding on an industrial scale. In special columns, direct synthesis is carried out - 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 for the reaction of nitrogen and oxygen to begin, strong heating is necessary. Electric arc and 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) N 2 O);
- +2 (nitrogen monoxide NO);
- +3 (nitric oxide (III) N 2 O 3 ; nitrous acid HNO 2 , its salts are nitrites);
- +4 (nitrogen dioxide (IV) NO 2 );
- +5 (nitrogen pentoxide (V) N 2 O 5 , nitric acid HNO 3 , nitrates).
Value in nature
Plants absorb ammonium ions and nitrate anions from the soil, use for the chemical reactions the synthesis of organic molecules, constantly going on in the 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, enriches the soil with it.
During tropical showers, atmospheric nitrogen oxidation reactions occur. Oxides dissolve to form acids; these nitrogen compounds in water enter the soil. Due to the cycle of the element in nature, its reserves in the earth's crust and air are constantly being replenished. Complex organic molecules containing nitrogen are decomposed by bacteria into inorganic components.
Practical use
The most important nitrogen compounds for agriculture are highly soluble salts. Urea, nitrate (sodium, potassium, calcium), ammonium compounds (aqueous ammonia, chloride, sulfate, ammonium nitrate) are absorbed by plants.
The inert properties of nitrogen, the inability of plants to absorb it from the air, make it necessary to introduce large doses of nitrates annually. Parts of the plant body are capable of storing the macro for the future, which affects the quality of the products. Excess nitrates in fruits and vegetables can cause poisoning in people and the growth of malignant neoplasms. In addition to agriculture, nitrogen compounds are used in other industries:
- to receive medication;
- for the chemical synthesis of macromolecular compounds;
- in the production of explosives from trinitrotoluene (TNT);
- for the release of dyes.
NO oxide is used in surgery, the substance has an analgesic effect. The first researchers of the chemical properties of nitrogen noticed a loss of sensation when inhaling this gas. So the trivial name “laughing gas” appeared.
The problem of nitrates in agricultural products
The nitrate salts of nitric acid contain a single-charged NO 3- anion. The old name for this group of substances, saltpeter, is still used. Nitrates are used to fertilize fields in greenhouses and gardens. They are brought in early spring before sowing, in the summer - in the form of liquid top dressing. The substances themselves do not pose a great danger to people, but in the body they turn into nitrites, then into nitrosamines. Nitrite ions NO 2- are toxic particles, they cause the oxidation of ferrous iron in hemoglobin molecules to ferric 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 the tissues.
What is the danger of nitrate contamination of food for human health:
- malignant tumors that occur when nitrates are converted to nitrosamines (carcinogens);
- the development of ulcerative colitis,
- hypotension or hypertension;
- heart failure;
- bleeding disorder
- lesions of the liver, pancreas, the development of diabetes;
- the development of renal failure;
- anemia, impaired memory, attention, intelligence.
The simultaneous use of different products with large 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 in food. Researchers have found that higher doses of hazardous compounds are found in immature and greenhouse plant products.
Phosphorus - 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 atomic structure of the elements is 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 phosphorus reactions occur at ordinary temperatures; this is a chemically active element. It interacts with oxygen to form the higher oxide P 2 O 5 . An aqueous solution of this substance has the properties of an acid (metaphosphoric). When it is heated, phosphoric acid is obtained. It forms several types of salts, many of which serve as mineral fertilizers, such as superphosphates. Compounds of nitrogen and phosphorus form an important part of the cycle of substances and energy on our planet, and are used in industrial, agricultural and other fields of activity.