The nitrogen subgroup occupies the fifth group (the main subgroup) in the table of Dmitry Ivanovich Mendeleev. It includes several elements, each of which deserves a detailed study and consideration.
a brief description of
Nitrogen is the most important component of the Earth’s atmosphere (78% of the volume). In the biosphere, it is part of protein molecules, it is considered the main element for the formation of life on our planet. In the lithosphere, elements of the nitrogen subgroup are found in the form of nitrates, phosphates.
Natural nitrogen is a combination of two isotopes:
- 99.635% of the mass is 14 N;
- 0.365% of the mass includes 15 N.
Phosphorus is considered an integral component of living organisms. In nature, it is in the form of phosphates (minerals).
Bismuth, antimony, arsenic are widely found in nature as part of sulfide ores. Arsenic is an important element responsible for hair growth. Its compounds are poisonous, in small doses they are used in veterinary medicine and medicine.
Phosphorus is in demand in aviation, agriculture, and medicine.
Structural Features of Atoms
The nitrogen subgroup contains five valence electrons on the last energy layer. Representatives of this group can give them in the course of chemical interactions or take three electrons from other atoms, completing the external energy level. That is why the nitrogen subgroup has oxidation states from -3 to +5. Higher oxides are acidic in nature, have the general formula R 2 O 5 .
A subgroup of nitrogen forms volatile hydrogen compounds of the composition RH 3 .
Change Properties
Elements of the analyzed subgroup exhibit non-metallic properties. Their ability to attract electrons is lower than that of the representatives of the subgroup of chalcogenes and halogens. What is the difference between the nitrogen subgroup? Properties of a metallic nature (reducing ability) increase from nitrogen to bismuth, as the radius of the atom increases.
Physical properties
Phosphorus and nitrogen are typical non-metals, antimony and arsenic exhibit dual properties, and bismuth is a typical metal. A practical subgroup of nitrogen has typical physical properties. Nitrogen is a gaseous substance of molecular structure, without taste, odor, it is soluble in water. Phosphorus, which has a tetrahedral structure, is a soft solid with insignificant solubility in water.
Arsenic is a solid substance with a metallic luster at a break. This compound is insoluble in water, has an insignificant conductivity of electric current.
Bismuth is a pink-white, crystalline, brittle substance that has insignificant electrical conductivity.
Nitrogen characteristic
It is with this chemical element that the nitrogen subgroup begins. The general characteristic of this element should begin with the fact that it exhibits pronounced non-metallic properties. Only nitrogen is not able to increase its valencies. He has seven electrons, which are located on two energy levels. Five electrons are located on the external level, therefore, nitrogen is able to exhibit the following oxidation states: - 3, + 5, -2, -1, + 1, + 2, + 3, + 4.
Under normal conditions, nitrogen is a molecular, inactive, gaseous substance. This diatomic molecule does not react with oxygen, a little lighter than air. When compressed, nitrogen turns into a snowy mass. This gas does not support combustion, respiration. At room temperature, it is able to interact only with lithium, forming its nitride.
To break a nitrogen molecule, you need to spend 942 kJ / mol of energy. All chemical interactions, in which molecular nitrogen becomes a participant, are associated with a change in the oxidation state, and nitrogen is capable of exhibiting the properties of both a reducing agent and an oxidizing agent.
When heated, it is able to interact with metals. At high temperatures, it reacts with some non-metals.
If nitrogen interacted at room temperature, it would form oxides with atmospheric oxygen, which would make it impossible for living organisms to exist on earth.
Nitrogen use
In industry, it is obtained from air, using the difference in boiling points of oxygen and nitrogen. This substance is used in the chemical industry for the synthesis of ammonia, the production of urea. It is also needed for creating electric lamps, drying explosive compounds, and pumping flammable liquids. The subgroup of nitrogen and phosphorus is characterized by compounds in demand in various industries. Let us dwell on some of them.
Ammonia
It can be considered the most important hydrogen compound of nitrogen, which is of great practical importance. Bacteria convert nitrogen molecules to ammonia. It is a colorless gas that has a pungent odor. It is significantly lighter than air, it is highly soluble in water. In redox processes, it exhibits reducing properties. Ammonia interacts with oxygen to form pure nitrogen or nitric oxide (2), and forms ammonium salts with inorganic acids. They are needed for the manufacture of explosives, electric batteries.
It is used for the manufacture of nitric acid and mineral nitrogen-containing compounds. In liquid form, it is used in the refrigeration industry. In medicine, it is necessary for the manufacture of ammonia, and in everyday life it serves as an excellent means for removing stains.
Nitrogen oxides
The fifth group and subgroup of nitrogen is characterized by the ability to form several types of oxides at once. For example, nitrogen forms a whole group of compounds with oxygen.
Brown gas (nitric oxide IV) is a gaseous compound with a specific odor. The substance dissolves in water, has the properties of an acid oxide, decomposes when heated, toxic.
Nitric anhydride (nitric oxide V) is a crystalline compound of white color. When heated, the substance decomposes, exhibits toxic properties.
Nitric acid and its salts
The nitrogen subgroup, the carbon subgroup are characterized by the formation of hydroxides, which have acidic properties.
There are three elements in the nitric acid molecule, between which covalent polar bonds exist. This molecular compound, in which nitrogen exhibits a maximum oxidation state (+5) with valency IV, is a colorless liquid that smokes in air and has a pungent odor.
Concentrated nitric acid is yellow. Its density is 1.51 g / cm 3 . It dissolves in water, exhibits the properties of a strong electrolyte.
In dilute form, nitric acid has the same chemical properties as other mineral acids. At room temperature, nitric acid decomposes into brown gas and water, so the compound is stored in a cool, dark place.
Concentrated acid destroys organic substances, it is able to interact even with metals, which are located in a series of stresses of metals after hydrogen.
Nitrates (salts of nitric acid) are obtained by the interaction of acid with metals, bases, basic oxides, and ammonia. They are solids having good solubility in water, are strong electrolytes.
With increasing temperature, nitrates decompose. A qualitative reaction to the nitrate ion is the interaction with copper chips (in the presence of concentrated sulfuric acid). A sign of the process is the release of brown gas.
Solid salts are determined by adding them to the flame of an alcohol lamp. A bright flash is a confirmation of the presence of nitrate, as they are explosive compounds.
Conclusion
Among the elements that make up the nitrogen subgroup, phosphorus is also of interest. It has a larger atomic radius, so non-metallic properties are weaker. This chemical element exhibits oxidation states of 3, + 3, + 5. In its free form, phosphorus is able to form several allotropic modifications: red, white, black. In chemical interactions, it exhibits both oxidizing and reducing properties. For example, white phosphorus has a molecular crystal lattice, this substance glows in the dark, is a strong poison.
Red phosphorus does not dissolve in water; when heated to its melting point, it passes into another allotropic modification.
Black phosphorus has semiconductor properties, it is heavier than other allotropic forms, outwardly similar to graphite.
Among the compounds that phosphorus forms, its oxides are of interest.
So, phosphorus oxide (V) is hygroscopic, therefore it is used in the chemical industry for drying gaseous compounds.
At the same time, it turns into an amorphous mass - HPO 3 . In case of boiling, phosphoric acid is formed from phosphorus (V) oxide. H 3 PO 4 is a white crystalline substance, highly soluble in water. This compound is a strong electrolyte.
A large amount of phosphorus is spent on the manufacture of incendiary shells, bombs, smoke bombs. Salts of phosphoric acid are used in agriculture as mineral fertilizers. All elements of the fifth group (main subgroup) at the external level contain the same number of electrons, which can be considered a common feature.