Phosphorus compounds 3. White phosphorus: properties, history of discovery and application

DEFINITION

Phosphorus- the fifteenth element of the periodic table. Designation - P from the Latin "phosphorus". Located in the third period, VA group. Refers to non-metals. The nuclear charge is 15.

Phosphorus is one of the fairly common elements; its content in the earth's crust is about 0.1% (wt). Due to its easy oxidation, phosphorus does not occur in a free state in nature.

Of the natural phosphorus compounds, the most important is calcium orthophosphate Ca 3 (PO 4) 2, which sometimes forms large deposits in the form of the mineral phosphorine. The mineral apatite is also often found, containing in addition to Ca 3 (PO 4) 2, also CaF 2 or CaCl 2.

Atomic and molecular mass of phosphorus

DEFINITION

Relative molecular mass of the substance (Mr) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and relative atomic mass of an element (A r)— how many times the average mass of atoms of a chemical element is greater than 1/12 the mass of a carbon atom.

The atomic and molecular masses of phosphorus are the same; they are equal to 30.9737.

Allotropy and allotropic modifications of phosphorus

Phosphorus forms several allotropic modifications.

White phosphorus obtained in the solid state by rapid cooling of phosphorus vapor; its density is 1.83 g/cm3. In its pure form, white phosphorus is completely colorless and transparent (Fig. 1). It is fragile in the cold, but at temperatures above 15 o C it becomes soft and can be easily cut with a knife.

In air, white phosphorus oxidizes very quickly and glows in the dark. Already with low heating, for which simply friction is enough, phosphorus ignites and burns. It has a molecular crystal lattice, at the nodes of which there are tetrahedral P4 molecules. Strong poison.

Rice. 1. Allotropic modifications of phosphorus. Appearance.

If white phosphorus is heated to a temperature of 250-300 o C, it transforms into another modification that has a red-violet color and is called red phosphorus. This transformation occurs very slowly and under the influence of light.

Red phosphorus is very different in its properties from white phosphorus: it oxidizes slowly in air, does not glow in the dark, lights up only at 260 o C and is non-toxic.

When heated strongly, red phosphorus evaporates (sublimates) without melting. When the vapor is cooled, white phosphorus is obtained.

Black phosphorus is formed from white phosphorus when heated to 200-220 o C under very high pressure. It looks like graphite, feels greasy to the touch and is heavier than other modifications. Semiconductor.

Isotopes of phosphorus

It is known that in nature phosphorus is found in the form of the only isotope 31 P (23.99%). The mass number is 31. The nucleus of an atom of the phosphorus isotope 31P contains fifteen protons and sixteen neutrons.

There are artificial isotopes of phosphorus with mass numbers from 24 to 46, among which the most stable is 32 P with a half-life of 14 days.

Phosphorus ions

The outer energy level of the phosphorus atom has five electrons, which are valence electrons:

1s 2 2s 2 2p 6 3s 2 3p 3 .

As a result of chemical interaction, phosphorus can lose its valence electrons, i.e. be their donor, and turn into positively charged ions or accept electrons from another atom, i.e. be their acceptor and turn into negatively charged ions:

P 0 -5e → P 5+ ;

P 0 -3e → P 3+ ;

P 0 -1e → P 1+ ;

P 0 +3e → P 3- .

Phosphorus molecule and atom

The phosphorus molecule is monatomic - P. Here are some properties that characterize the phosphorus atom and molecule:

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	Phosphine can be prepared by the action of hydrochloric acid on calcium phosphide. Calculate the volume of phosphine (no.) that is formed from 9.1 g of calcium phosphide. The mass fraction of the product yield is 90%.
Solution	Let us write the equation for the reaction of producing phosphine from calcium phosphide: Ca 3 P 2 + 6HCl = 2PH 3 + 3CaCl 2. Let's calculate the amount of calcium phosphide substance (molar mass - 182 g/mol): n(PH 3) = m(PH 3) / M(PH 3); n(PH 3) = 9.1 / 182 = 0.05 mol. According to the reaction equation n(PH 3) : n(Ca 3 P 2) = 2:1, it means: n(PH 3) = 2 × n(Ca 3 P 2); n(PH 3) = 2 × 0.05 = 0.1 mol. Then, the volume of released phosphine will be equal to: V(PH 3) = n (PH 3) × V m; V(PH 3) = 0.1 × 22.4 = 2.24 l. Taking into account the yield of the reaction product, the volume of phosphine is: V(PH 3) = V(PH 3) × η/100%; V(PH 3) = 2.24 × 90/100% = 2.016 l.
Answer	The volume of phosphine is 2.016 l

Phosphorus and its compounds

Introduction

Chapter I. Phosphorus as an element and as a simple substance

1.1. Phosphorus in nature

1.2. Physical properties

1.3. Chemical properties

1.4. Receipt

1.5. Application

Chapter II. Phosphorus compounds

2.1. Oxides

2.2. Acids and their salts

2.3. Phosphine

Chapter III. Phosphorus fertilizers

Conclusion

Bibliography

Introduction

Phosphorus (lat. Phosphorus) P – chemical element Group V periodic table Mendeleev atomic number 15, atomic mass 30.973762(4). Let's consider the structure of the phosphorus atom. The outer energy level of the phosphorus atom contains five electrons. Graphically it looks like this:

1s 2 2s 2 2p 6 3s 2 3p 3 3d 0

In 1699, the Hamburg alchemist H. Brand, in search of a “philosopher’s stone” supposedly capable of turning base metals into gold, when evaporating urine with coal and sand, isolated a white waxy substance that could glow.

The name "phosphorus" comes from the Greek. “phos” – light and “phoros” – carrier. In Russia, the term “phosphorus” was introduced in 1746 by M.V. Lomonosov.

The main phosphorus compounds include oxides, acids and their salts (phosphates, dihydrogen phosphates, hydrogen phosphates, phosphides, phosphites).

A lot of phosphorus-containing substances are found in fertilizers. Such fertilizers are called phosphorus fertilizers.

Chapter I Phosphorus as an element and as a simple substance

1.1 Phosphorus in nature

Phosphorus is one of the common elements. The total content in the earth's crust is about 0.08%. Due to its easy oxidation, phosphorus occurs in nature only in the form of compounds. The main phosphorus minerals are phosphorites and apatites, of the latter the most common is fluorapatite 3Ca3 (PO4)2 CaF2. Phosphorites are widespread in the Urals, Volga region, Siberia, Kazakhstan, Estonia, and Belarus. The largest deposits of apatite are located on the Kola Peninsula.

Phosphorus – necessary element living organisms. It is present in bones, muscles, brain tissue and nerves. ATP molecules are built from phosphorus - adenosine triphosphoric acid (ATP is a collector and carrier of energy). The adult human body contains on average about 4.5 kg of phosphorus, mainly in combination with calcium.

Phosphorus is also found in plants.

Natural phosphorus consists of only one stable isotope 31 R. Today, six radioactive isotopes of phosphorus are known.

1.2 Physical properties

Phosphorus has several allotropic modifications - white, red, black, brown, violet phosphorus, etc. The first three of these are the most studied.

White phosphorus- a colorless, yellowish-tinged crystalline substance that glows in the dark. Its density is 1.83 g/cm3. Insoluble in water, soluble in carbon disulfide. Has a characteristic garlic smell. Melting point 44°C, auto-ignition temperature 40°C. To protect white phosphorus from oxidation, it is stored under water in the dark (in the light it transforms into red phosphorus). In the cold, white phosphorus is fragile; at temperatures above 15°C it becomes soft and can be cut with a knife.

White phosphorus molecules have a crystal lattice, at the nodes of which there are P4 molecules, shaped like a tetrahedron.

Each phosphorus atom is connected by three σ bonds to the other three atoms.

White phosphorus is poisonous and causes hard-to-heal burns.

Red phosphorus– powdery substance dark red odorless, does not dissolve in water and carbon disulfide, does not glow. Ignition temperature 260°C, density 2.3 g/cm3. Red phosphorus is a mixture of several allotropic modifications that differ in color (from scarlet to violet). The properties of red phosphorus depend on the conditions of its production. Not poisonous.

Black phosphorus By appearance similar to graphite, greasy to the touch, has semiconductor properties. Density 2.7 g/cm3.

Red and black phosphorus have an atomic crystal lattice.

1.3 Chemical properties

Phosphorus is a non-metal. In compounds, it usually exhibits an oxidation state of +5, less often – +3 and –3 (only in phosphides).

Reactions with white phosphorus are easier than with red phosphorus.

I. Interaction with simple substances.

1. Interaction with halogens:

2P + 3Cl2 = 2PCl3 (phosphorus (III) chloride),

PCl3 + Cl2 = PCl5 (phosphorus (V) chloride).

2. Interaction with non-metals:

2P + 3S = P2 S3 (phosphorus (III) sulfide.

3. Interaction with metals:

2P + 3Ca = Ca3 P2 (calcium phosphide).

4. Interaction with oxygen:

4P + 5O2 = 2P2 O5 (phosphorus (V) oxide, phosphoric anhydride).

II. Interaction with complex substances.

1.4 Receipt

Phosphorus is obtained from crushed phosphorites and apatites, the latter are mixed with coal and sand and calcined in furnaces at 1500°C:

2Ca3 (PO4)2 + 10C + 6SiO26CaSiO3 + P4 + 10CO.

Phosphorus is released in the form of vapor, which condenses in the receiver under water, forming white phosphorus.

When heated to 250-300°C without air access, white phosphorus turns into red.

Black phosphorus is obtained by prolonged heating of white phosphorus at very high pressure (200°C and 1200 MPa).

1.5 Application

Red phosphorus is used in the manufacture of matches (see picture). It is part of the mixture applied to lateral surface matchbox. The main component of the match head is Berthollet salt KClO3. Due to the friction of the match head against the lubricant, the phosphorus particles in the air ignite. As a result of the oxidation reaction of phosphorus, heat is released, leading to the decomposition of Berthollet salt.

The resulting oxygen helps ignite the match head.

Phosphorus is used in metallurgy. It is used to produce conductors and is a component of some metallic materials, such as tin bronzes.

Phosphorus is also used in the production of phosphoric acid and pesticides (dichlorvos, chlorophos, etc.).

White phosphorus is used to create smoke screens, since its combustion produces white smoke.

Chapter II . Phosphorus compounds

2.1 Oxides

Phosphorus forms several oxides. The most important of them are phosphorus oxide (V) P4 O10 and phosphorus oxide (III) P4 O6. Often their formulas are written in a simplified form - P2 O5 and P2 O3. The structure of these oxides retains the tetrahedral arrangement of phosphorus atoms.

Phosphorus oxide(III) P4 O6 is a waxy crystalline mass that melts at 22.5°C and turns into a colorless liquid. Poisonous.

When dissolved in cold water forms phosphorous acid:

P4 O6 + 6H2 O = 4H3 PO3,

and when reacting with alkalis - the corresponding salts (phosphites).

Strong reducing agent. When interacting with oxygen, it is oxidized to P4 O10.

Phosphorus (III) oxide is obtained by the oxidation of white phosphorus in the absence of oxygen.

Phosphorus oxide(V) P4 O10 is a white crystalline powder. Sublimation temperature 36°C. It has several modifications, one of which (the so-called volatile) has the composition P4 O10. The crystal lattice of this modification is composed of P4 O10 molecules connected to each other by weak intermolecular forces, which are easily broken when heated. Hence the volatility of this variety. Other modifications are polymeric. They are formed by endless layers of PO4 tetrahedra.

When P4 O10 interacts with water, phosphoric acid is formed:

P4 O10 + 6H2 O = 4H3 PO4.

Being an acidic oxide, P4 O10 reacts with basic oxides and hydroxides.

It is formed during high-temperature oxidation of phosphorus in excess oxygen (dry air).

Due to its exceptional hygroscopicity, phosphorus (V) oxide is used in laboratory and industrial technology as a drying and dehydrating agent. In its drying effect it surpasses all other substances. Chemically bound water is removed from anhydrous perchloric acid to form its anhydride:

4HClO4 + P4 O10 = (HPO3)4 + 2Cl2 O7.

2.2 Acids and their salts

A) Phosphorous acid H3 PO3. Anhydrous phosphorous acid H3 PO3 forms crystals with a density of 1.65 g/cm3, melting at 74°C.

Structural formula:

When anhydrous H3 PO3 is heated, a disproportionation reaction (auto-oxidation-self-reduction) occurs:

4H3 PO3 = PH3 + 3H3 PO4.

Phosphorous acid salts – phosphites. For example, K3 PO3 (potassium phosphite) or Mg3 (PO3)2 (magnesium phosphite).

Phosphorous acid H3 PO3 is obtained by dissolving phosphorus (III) oxide in water or hydrolysis of phosphorus (III) chloride PCl3:

РCl3 + 3H2 O = H3 PO3 + 3HCl.

b) Phosphoric acid (orthophosphoric acid) H3 PO4 .

Anhydrous phosphoric acid appears as light transparent crystals that diffuse in air at room temperature. Melting point 42.35°C. Phosphoric acid forms solutions of any concentration with water.

Phosphoric acid has the following structural formula:

Phosphoric acid reacts with metals located in a series of standard electrode potentials up to hydrogen, with basic oxides, with bases, and with salts of weak acids.

In the laboratory, phosphoric acid is obtained by oxidizing phosphorus with 30% nitric acid:

3P + 5HNO3 + 2H2 O = 3H3 PO4 + 5NO.

In industry, phosphoric acid is produced in two ways: extraction and thermal. At the core extraction method lies the processing of crushed natural phosphates with sulfuric acid:

Ca3 (PO4)2 + 3H2 SO4 = 2H3 PO4 + 3CaSO4 ↓.

The phosphoric acid is then filtered and concentrated by evaporation.

Thermal method consists of the reduction of natural phosphates to free phosphorus, followed by its combustion to P4 O10 and dissolution of the latter in water. Produced according to this method phosphoric acid is characterized by higher purity and increased concentration(up to 80% mass).

Phosphoric acid is used to produce fertilizers, to prepare reagents, organic substances, and to create protective coatings on metals. Purified phosphoric acid is needed for the preparation of pharmaceuticals and feed concentrates.

Phosphoric acid is not a strong acid. As a tribasic acid, aqueous solution dissociates stepwise. Dissociation is easier at the first stage.

1. H3 PO4H+ + (dihydrogen phosphate ion);

2. H+ + (hydrogen phosphate ion);

3. H+ + (phosphate ion).

Total ionic equation dissociation of phosphoric acid:

Phosphoric acid forms three series of salts:

a) K3 PO4, Ca3 (PO4)2 – trisubstituted, or phosphates;

b) K2 HPO4, CaHPO4 – disubstituted, or hydrophosphates;

c) KH2 PO4, Ca(H2 PO4)2 – monosubstituted, or dihydrogen phosphates.

Monosubstituted phosphates are acidic, dibasic phosphates are slightly alkaline, and tribasic phosphates are alkaline.

All alkali metal and ammonium phosphates are soluble in water. Of the calcium salts of phosphoric acid, only calcium dihydrogen phosphate dissolves in water. Calcium hydrogen phosphate and calcium phosphate are soluble in organic acids.

When heated, phosphoric acid first loses water - the solvent, then dehydration of phosphoric acid begins and diphosphoric acid is formed:

2H3 PO4 = H4 P2 O7 + H2 O.

A significant part of phosphoric acid is converted into diphosphoric acid at a temperature of about 260°C.

V) Phosphoric acid (hypophosphoric acid) H4 P2 O6 .

.

H4 P2 O6 is a tetrabasic acid of medium strength. During storage, hypophosphoric acid gradually decomposes. When its solutions are heated, it turns into H3 PO4 and H3 PO3.

Formed during the slow oxidation of H3 PO3 in air or the oxidation of white phosphorus in humid air.

G) Hypophosphorous acid (hypophosphorous acid) H3PO2. This acid is monobasic and strong. Hypophosphorous acid has the following structural formula:

.

Hypophosphites– salts of hypophosphorous acid – usually highly soluble in water.

Hypophosphites and H3 PO2 are energetic reducing agents (especially in an acidic environment). Their valuable feature is the ability to reduce dissolved salts of some metals (Ni, Cu, etc.) to free metal:

2Ni2+ + + 2H2 O → Ni0+ + 6H+ .

Hypophosphorous acid is obtained by decomposing calcium or barium hypophosphites with sulfuric acid:

Ba(H2 PO2)2 + H2 SO4 = 2H3 PO2 + BaSO4 ↓.

Hypophosphites are formed by boiling white phosphorus in suspensions of calcium or barium hydroxides.

2P4 (white) + 3Ba(OH)2 + 6H2 O = 2PH3 + 3Ba(H2 PO2)2.

2.3 Phosphine

Phosphine PH3 - a compound of phosphorus with hydrogen - a colorless gas with a sharp, unpleasant garlic odor, highly soluble in water (does not react chemically with it), and is very toxic. In air, pure and dry phosphine ignites when heated above 100-140°C. If phosphine contains impurities of diphosphine P2 H4, it spontaneously ignites in air.

When interacting with some strong acids, phosphine forms phosphonium salts, For example:

PH3 + HCl = PH4 Cl (phosphonium chloride).

The structure of the phosphonium cation [PH4]+ is similar to the structure of the ammonium cation +.

Water decomposes phosphonium salts to form phosphine and hydrogen halide.

Phosphine can be obtained by reacting phosphides with water:

Ca3 P2 + 6H2 O = 3Ca(OH)2 + 2PH3.

And one last thing. When phosphorus interacts with metals, salts are formed - phosphides. For example, Ca3 P2 (calcium phosphide), Mg3 P2 (magnesium phosphide).

Chapter III Phosphorus fertilizers

Phosphorus compounds, like nitrogen, constantly undergo transformations in nature - the phosphorus cycle occurs in nature. Plants extract phosphates from the soil and convert them into complex phosphorus compounds. organic matter. These substances with plant foods enter the body of animals - the formation of protein substances in nervous and muscle tissues, calcium phosphates in bones, etc. occurs. After the death of animals and plants, phosphorus-containing compounds decompose under the action of microorganisms. As a result, phosphates are formed. Thus, the cycle expressed by the diagram is completed:

P (living organisms) P (soil).

This cycle is disrupted when phosphorus compounds are removed from crop yields. The lack of phosphorus in the soil is practically not replenished naturally. Therefore, it is necessary to apply phosphorus fertilizers.

As you know, mineral fertilizers can be simple or complex. Simple fertilizers include fertilizers containing one nutrient element. Complex fertilizers contain several nutrients.

How are phosphate fertilizers produced in industry? Natural phosphates do not dissolve in water, and are poorly soluble in soil solutions and are poorly absorbed by plants. Processing natural phosphates into water-soluble compounds is a challenge chemical industry. Contents in fertilizer nutrient element Phosphorus is assessed by the content of phosphorus oxide (V) P2 O5.

Main component phosphorus fertilizers - calcium dihydrogen or hydrogen phosphates. Phosphorus is part of many organic compounds in plants. Phosphorus nutrition regulates the growth and development of plants. The most common phosphorus fertilizers include:

1.Phosphorite flour– fine white powder. Contains 18-26% P2 O5.

It is obtained by grinding phosphorites Ca3 (PO4)2.

Phosphorite flour can only be absorbed on podzolic and peat soils containing organic acids.

2. Simple superphosphate– gray fine-grained powder. Contains up to 20% P2 O5.

It is obtained by reacting natural phosphate with sulfuric acid:

Ca3 (PO4)2 + 2H2 SO4 = Ca(H2 PO4)2 + 2CaSO4.

superphosphate

In this case, a mixture of salts Ca(H2PO4)2 and CaSO4 is obtained, which is well absorbed by plants in any soil.

3. Double superphosphate(color and appearance similar to simple superphosphate).

It is obtained by acting on natural phosphate with phosphoric acid:

Ca3 (PO4)2 + 4H3 PO4 = 3Ca(H2 PO4)2.

Compared to simple superphosphate, it does not contain CaSO4 and is a much more concentrated fertilizer (contains up to 50% P2 O5).

4. Precipitate– contains 35-40% P2 O5.

Obtained by neutralizing phosphoric acid with a solution of calcium hydroxide:

H3 PO4 + Ca(OH)2 = CaHPO4 2H2 O.

Used on acidic soils.

5. Bone flour. Obtained by processing the bones of domestic animals, it contains Ca3 (PO4)2.

6. Ammophos– a complex fertilizer containing nitrogen (up to 15% K) and phosphorus (up to 58% P2 O5) in the form of NH4 H2 PO4 and (NH4)2 HPO4. It is obtained by neutralizing phosphoric acid with ammonia.

Conclusion

And in conclusion, I would like to say the biological significance of phosphorus. Phosphorus is integral part tissues of human, animal and plant organisms. In the human body, most phosphorus is bound to calcium. To build a skeleton, a child needs as much phosphorus as calcium. In addition to bones, phosphorus is found in nervous and brain tissues, blood, and milk. In plants, as in animals, phosphorus is part of proteins.

From phosphorus that enters the human body with food, mainly eggs, meat, milk and bread, ATP is built - adenosine triphosphoric acid, which serves as a collector and carrier of energy, as well as nucleic acids - DNA and RNA, which transmit the hereditary properties of the body. ATP is consumed most intensively in actively working organs of the body: the liver, muscles, and brain. It is not for nothing that the famous mineralogist, one of the founders of the science of geochemistry, Academician A. E. Fersman called phosphorus “the element of life and thought.”

As stated, phosphorus exists in nature in the form of compounds found in soil (or dissolved in natural waters). Phosphorus is extracted from the soil by plants, and animals obtain phosphorus from plant foods. After the death of plant and animal organisms, phosphorus returns to the soil. This is how the phosphorus cycle occurs in nature.

Bibliography:

1. Akhmetov N.S. Chemistry 9th grade: textbook. for general education textbook establishments. – 2nd ed. – M.: Education, 1999. – 175 p.: ill.

2. Gabrielyan O.S. Chemistry 9th grade: textbook. for general education textbook establishments. – 4th ed. – M.: Bustard, 2001. – 224 p.: ill.

3. Gabrielyan O.S. Chemistry grades 8-9: method. allowance. – 4th ed. – M.: Bustard, 2001. – 128 p.

4. Eroshin D.P., Shishkin E.A. Methods for solving problems in chemistry: textbook. allowance. – M.: Education, 1989. – 176 p.: ill.

5. Kremenchugskaya M. Chemistry: A schoolchild’s reference book. – M.: Philol. Society "WORD": LLC "AST Publishing House", 2001. - 478 p.

6. Kritsman V.A. Book to read inorganic chemistry. – M.: Education, 1986. – 273 p.

Forest-steppe soils

characterized by a humus content of 1.78-2.46%.

Powerful black soils

contain 0.81-1.25% humus matter.

Ordinary chernozems

contain 0.90-1.27% humus matter.

Leached chernozems

contain 1.10-1.43% of humic matter.

Dark chestnut soils contain

in humic matter 0.97-1.30%.

Role in the plant

Biochemical functions

Oxidized phosphorus compounds are necessary for all living organisms. No living cell can exist without them.

In plants, phosphorus is found in organic and mineral compounds. At the same time, the content of mineral compounds ranges from 5 to 15%, organic compounds - 85-95%. Mineral compounds are represented by potassium, calcium, ammonium and magnesium salts of orthophosphoric acid. Plant mineral phosphorus - reserve substance, a reserve for the synthesis of phosphorus-containing organic compounds. It increases the buffering capacity of cell sap, maintains cell turgor and other equally important processes.

Organic compounds- nucleic acids, adenosine phosphates, sugar phosphates, nucleoproteins and phosphatoproteins, phosphatides, phytin.

In first place in importance for plant life are nucleic acids (RNA and DNA) and adenosine phosphates (ATP and ADP). These compounds are involved in many vital processes of the plant organism: protein synthesis, energy metabolism, transmission of hereditary properties.

Nucleic acids

Adenosine phosphates

Special role Phosphorus in plant life is to participate in the energy metabolism of the plant cell. the main role V this process belongs to adenosine phosphates. They contain phosphoric acid residues linked by high-energy bonds. When hydrolyzed, they are capable of releasing significant amounts of energy.

They represent a kind of energy accumulator, supplying it as needed to carry out all processes in the cell.

There are adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP). The latter significantly exceeds the first two in energy reserves and occupies a leading role in energy metabolism. It consists of adenine (a purine base) and a sugar (ribose), as well as three phosphoric acid residues. ATP synthesis occurs in plants during respiration.

Phosphatides

Phosphatides, or phospholipids, are esters of glycerol, high molecular weight fatty acids and phosphoric acid. They are part of phospholipid membranes and regulate the permeability of cellular organelles and plasmalemma to various substances.

The cytoplasm of all plant cells contains lecithin, a member of the phosphatide group. This is a derivative of diglyceride phosphoric acid, a fat-like substance containing 1.37% .

Sugar phosphates

Sugar phosphates, or phosphorus esters of sugars, are present in all plant tissues. More than a dozen compounds of this type are known. They perform important role in the processes of respiration and photosynthesis in plants. The formation of sugar phosphates is called phosphorylation. The content of sugar phosphates in the plant, depending on age and nutritional conditions, varies from 0.1 to 1.0% of dry weight.

Fitin

Phytin is a calcium-magnesium salt of inositol phosphoric acid, containing 27.5%. It ranks first in terms of content in plants among other phosphorus-containing compounds. Phytin is present in young organs and tissues of plants, especially in seeds, where it serves as a reserve substance and is used by seedlings during the germination process.

Main functions of phosphorus

Most phosphorus is present in the reproductive organs and young parts of plants. Phosphorus is responsible for accelerating the formation of plant root systems. The main amount of phosphorus is consumed in the first phases of development and growth. Phosphorus compounds have the ability to easily move from old tissues to young ones and be reused (recycled).

Phosphorus - vital important element from the fifth group periodic table Mendeleev. The chemical properties of phosphorus depend on its modification. Most active substance is white phosphorus that oxidizes in air. Phosphorus has two valencies (III and V) and three oxidation states - +5, +3, -3.

Phosphorus and compounds

Phosphorus has three allotropic modifications, differing in chemical and physical properties:

• white;
• red;
• black.

Under phosphorus in chemical reactions most often understood as white phosphorus (P 4). Red phosphorus reacts under certain conditions. For example, it reacts with water when heated and under pressure. Black phosphorus is practically inert.

Rice. 1. Glowing white phosphorus.

Phosphorus reacts with simple and complex substances, forming:

• phosphine;
• phosphoric acid;
• phosphides;
• oxides

Phosphine (PH 3) is a poorly soluble poisonous gas, an analogue of ammonia. In the absence of oxygen, when heated, it decomposes into simple substances - phosphorus and hydrogen.

Rice. 2. Phosphine.

Phosphoric or orthophosphoric acid (H 3 PO 4) is formed when phosphorus or phosphorus (V) oxide reacts with water.

Phosphides are salts formed by interaction with metals or non-metals. They are unstable and easily decompose when exposed to acids or water.

Phosphorus can form two oxides - P 2 O 3 and P 2 O 5.

H 3 PO 4 is a medium-strength acid that exhibits amphoteric properties when interacting with a strong acid. Phosphoric acid forms phosphates.

Chemical properties

Basic Chemical properties phosphorus and its compounds are described in the table.

Substance	Reaction	Peculiarities	The equation
		With excess O 2 forms phosphorus oxide (V)	4P + 5O 2 → 2P 2 O 5 ; 4P + 3O 2 → 2P 2 O 3
	With metal	Is an oxidizing agent	3Mg + 2P → Mg 3 P 2
	With halogens and non-metals	Does not react with hydrogen	2P + 3S → P 2 S 3
			8P + 12H 2 O → 5PH 3 + 3H 3 PO 2
	With acids		2P + 5H 2 SO 4 → 2H 3 PO 4 + 5SO 2 + 2H 2 O
	With alkalis		P 4 + 3NaOH + 3H 2 O → PH 3 + 3NaH 2 PO 2
		Flammable in air	PH 3 + 2O 2 → H 3 PO 4
	With halogens and non-metals		PH 3 + 2I 2 + 2H 2 O → H(PH 2 O 2) + 4HI
	With acids	Exhibits reducing agent properties	PH 3 + 3H 2 SO 4 → H 2 (PHO 2) + 3SO 2 + 3H 2 O
	With metals	With active metals	2H 3 PO 4 + 3Ca → Ca 3 (PO 4) 2 + 3H 2
		Subject to dissociation	H 3 PO 4 + H 2 O ↔ H 3 O + + H2PO 4 –
	With alkalis	Forms acid or alkaline phosphates	H 3 PO 4 + 3NaOH → Na 3 PO 4 + 3H 2 O
	With oxides		2H 3 PO 4 + 3K 2 O → 2K 3 PO 4 + 3H 2 O
			2H 3 PO 4 + 3CaCO 3 → Ca 3 (PO 4) 2 + 3H 2 O + 3CO 2
	With ammonia		H 3 PO 4 + 3NH 3 → (NH 4) 3 PO 4
	With halogens and non-metals		2P 2 O 3 + 6Cl 2 → 4PCl 3 O + O 2; 2P 2 O 3 + 9S → P 4 S 6 + 3SO 2
		Reacts slowly with cold water and quickly with hot water	P 2 O 3 + 3H 2 O → 2H 3 PO 3
	With alkalis		P 2 O 3 + 4NaOH → 2Na 2 HPO 3 + H 2 O
		Reacts explosively	2P 2 O 5 + 6H 2 O → 4H 3 PO 4
	With acids	Substitution reaction	4HNO 3 + 2P 2 O 5 → 4HPO 3 + 2N 2 O 5
		Form metal hydroxides and phosphine	Ca 3 P 2 + 6H 2 O → 3Ca(OH) 2 + 2PH 3
	With acids	Substitution reaction	Ca 3 P 2 + 6HCl → 3CaCl 2 + 2PH 3

When heated, phosphorus oxide decomposes. Moreover, P 2 O 3 forms red phosphorus, and P 2 O 5 forms phosphorus (III) oxide and oxygen.

Rice. 3. Red phosphorus.

Usage

Phosphorus compounds are widely used:

• Fertilizers and detergents are obtained from phosphates;
• phosphoric acid is used to dye fabric;
• Phosphorus (V) oxide dries liquids and gases.

Red phosphorus is used in the production of matches and explosives.

What have we learned?

Phosphorus is an active non-metal that reacts with simple and complex substances. As a result of reactions, it forms oxides (III) and (V), phosphine, phosphoric acid and phosphides. Phosphorus compounds react with metals, non-metals, acids, alkalis, and water. Phosphorus and its compounds are used in industry and agriculture.

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Introduction

Phosphorus (lat. Phosphorus) P is a chemical element of group V of the periodic system of Mendeleev, atomic number 15, atomic mass 30.973762 (4). Let's consider the structure of the phosphorus atom. The outer energy level of the phosphorus atom contains five electrons. Graphically it looks like this:

1s 2 2s 2 2p 6 3s 2 3p 3 3d 0

In 1699, the Hamburg alchemist X. Brand, in search of a “philosopher’s stone” supposedly capable of turning base metals into gold, when evaporating urine with coal and sand, isolated a white waxy substance that could glow.

The name "phosphorus" comes from the Greek. “phos” - light and “phoros” - carrier. In Russia, the term “phosphorus” was introduced in 1746 by M.V. Lomonosov.

The main phosphorus compounds include oxides, acids and their salts (phosphates, dihydrogen phosphates, hydrogen phosphates, phosphides, phosphites).

A lot of phosphorus-containing substances are found in fertilizers. Such fertilizers are called phosphorus fertilizers.

Phosphorus as an element and as a simple substance

Phosphorus in nature

Phosphorus is one of the common elements. The total content in the earth's crust is about 0.08%. Due to its easy oxidation, phosphorus occurs in nature only in the form of compounds. The main phosphorus minerals are phosphorites and apatites, of the latter the most common is fluorapatite 3Ca 3 (PO 4) 2 * CaF 2. Phosphorites are widespread in the Urals, Volga region, Siberia, Kazakhstan, Estonia, and Belarus. The largest deposits of apatite are located on the Kola Peninsula.

Phosphorus is a necessary element of living organisms. It is present in bones, muscles, brain tissue and nerves. ATP molecules are built from phosphorus - adenosine triphosphoric acid (ATP is a collector and carrier of energy). The adult human body contains on average about 4.5 kg of phosphorus, mainly in combination with calcium.

Phosphorus is also found in plants.

Natural phosphorus consists of only one stable isotope 31 R. Today, six radioactive isotopes of phosphorus are known.

Physical properties

Phosphorus has several allotropic modifications - white, red, black, brown, violet phosphorus, etc. The first three of these are the most studied.

White phosphorus- a colorless, yellowish-tinged crystalline substance that glows in the dark. Its density is 1.83 g/cm3. Insoluble in water, soluble in carbon disulfide. Has a characteristic garlic smell. Melting point 44°C, auto-ignition temperature 40°C. To protect white phosphorus from oxidation, it is stored under water in the dark (in the light it transforms into red phosphorus). In the cold, white phosphorus is fragile; at temperatures above 15°C it becomes soft and can be cut with a knife.

Molecules of white phosphorus have a crystal lattice, at the nodes of which there are P 4 molecules, shaped like a tetrahedron.

Each phosphorus atom is connected by three?-bonds to the other three atoms.

White phosphorus is poisonous and causes hard-to-heal burns.

Red phosphorus- a powdery substance of a dark red color, odorless, insoluble in water and carbon disulfide, and does not glow. Ignition temperature 260°C, density 2.3 g/cm 3 . Red phosphorus is a mixture of several allotropic modifications that differ in color (from scarlet to violet). The properties of red phosphorus depend on the conditions of its production. Not poisonous.

Black phosphorus It looks like graphite, feels greasy to the touch, and has semiconductor properties. Density 2.7 g/cm3.

Red and black phosphorus have an atomic crystal lattice.

Chemical properties

Phosphorus is a non-metal. In compounds it usually exhibits an oxidation state of +5, less often - +3 and -3 (only in phosphides).

Reactions with white phosphorus are easier than with red phosphorus.

I. Interaction with simple substances.

1. Interaction with halogens:

2P + 3Cl 2 = 2PCl 3 (phosphorus (III) chloride),

PCl 3 + Cl 2 = PCl 5 (phosphorus (V) chloride).

2. Interaction with non-metals:

2P + 3S = P 2 S 3 (phosphorus (III) sulfide.

3. Interaction with metals:

2P + 3Ca = Ca 3 P 2 (calcium phosphide).

4. Interaction with oxygen:

4P + 5O 2 = 2P 2 O 5 (phosphorus (V) oxide, phosphoric anhydride).

II. Interaction with complex substances.

3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO^.

Receipt

Phosphorus is obtained from crushed phosphorites and apatites, the latter are mixed with coal and sand and calcined in furnaces at 1500°C:

2Ca 3 (PO 4) 2 + 10C + 6SiO 2 6CaSiO 3 + P 4 ^ + 10CO^.

Phosphorus is released in the form of vapor, which condenses in the receiver under water, forming white phosphorus.

When heated to 250-300°C without air access, white phosphorus turns into red.

Black phosphorus is obtained by prolonged heating of white phosphorus at very high pressure (200°C and 1200 MPa).

Application

Red phosphorus is used in the manufacture of matches (see picture). It is part of the mixture applied to the side surface of the matchbox. The main component of the match head is Berthollet salt KClO 3 . Due to the friction of the match head against the lubricant, the phosphorus particles in the air ignite. As a result of the oxidation reaction of phosphorus, heat is released, leading to the decomposition of Berthollet salt.

The resulting oxygen helps ignite the match head.

Phosphorus is used in metallurgy. It is used to produce conductors and is a component of some metallic materials, such as tin bronzes.

Phosphorus is also used in the production of phosphoric acid and pesticides (dichlorvos, chlorophos, etc.).

White phosphorus is used to create smoke screens, since its combustion produces white smoke.