Among the biogenic elements, a special place should be given to phosphorus. Indeed, without it, the existence of such vital compounds as, for example, ATP or phospholipids, as well as many others, is impossible. Moreover, the inorganic of this element is very rich in various molecules. Phosphorus and its compounds are widely used in industry, are important participants in biological processes, and are used in various fields of human activity. Therefore, we will consider what this element is, what is its simple substance and the most important compounds.

Phosphorus: general characteristics of the element

The position in the periodic table can be described in several points.

1. Fifth group, main subgroup.
2. Third Minor Period.
3. The serial number is 15.
4. The atomic mass is 30.974.
5. The electronic configuration of the atom is 1s 2 2s 2 2p 6 3s 2 3p 3.
6. Possible oxidation states from -3 to +5.
7. Chemical symbol - P, pronunciation in formulas "pe". The name of the element is phosphorus. The Latin name is Phosphorus.

The history of the discovery of this atom goes back to the distant XII century. Even in the records of the alchemists, there were information indicating the receipt of an unknown "luminous" substance. However, the official date for the synthesis and discovery of phosphorus was 1669. The bankrupt merchant Brand, in search of the Philosopher's Stone, accidentally synthesized a substance capable of emitting a glow and burning with a bright blinding flame. He did this by repeatedly calcining human urine.

After it, independently of each other, in approximately the same ways, this element was obtained:

• I. Kunkel;
• R. Boyle;
• A. Marggraf;
• K. Scheele;
• A. Lavoisier.

Today, one of the most popular methods for synthesizing this substance is reduction from the corresponding phosphorus-containing minerals at high temperatures under the influence of carbon monoxide and silica. The process is carried out in special ovens. Phosphorus and its compounds are very important substances both for living things and for many syntheses in the chemical industry. Therefore, one should consider what this element is as a simple substance and where it is found in nature.

Simple substance phosphorus

It is difficult to name any specific compound when it comes to phosphorus. This is due to the many allotropic modifications that this element has. There are four main types of the simple substance phosphorus.

1. White. This is a compound whose formula is P 4. It is a white volatile substance with a pungent, unpleasant odor of garlic. It ignites spontaneously in air at normal temperatures. Burns out with a luminous pale green light. Very poisonous and life-threatening. The chemical activity is extremely high, therefore, it is obtained and stored under a layer of purified water. This is possible due to poor solubility in polar solvents. Best suited for this white phosphorus is carbon disulfide and organic matter. When heated, it is capable of passing into the next allotropic form - red phosphorus. During condensation and cooling of vapors, it can form strata. Fatty to the touch, soft, easily cut with a knife, white (slightly yellowish). Melting point 44 0 С. Due to its chemical activity it is used in syntheses. But due to its toxicity, it has no wide industrial application.
2. Yellow. It is a poorly purified form of white phosphorus. It is even more poisonous, it also smells unpleasant of garlic. It ignites and burns with a bright glowing green flame. These yellow or brown crystals do not dissolve in water at all; upon complete oxidation, they emit clouds of white smoke with a composition of P 4 O 10.
3. Red phosphorus and its compounds are the most widespread and most commonly used industrial modification of this substance. The pasty red mass, which can transform into violet crystals under increased pressure, is chemically inactive. It is a polymer that can dissolve only in some metals and nothing else. At a temperature of 250 0 С it sublimes, turning into a white modification. It is not as poisonous as the previous forms. However, with prolonged exposure to the body, it is toxic. It is used in lighting matchboxes. This is explained by the fact that it cannot ignite spontaneously, but it explodes (ignites) during denotation and friction.
4. The black. According to external data, it is very similar to graphite, it is also greasy to the touch. It is a semiconductor of electric current. Dark crystals, shiny, which cannot be dissolved in any solvents at all. To ignite, very high temperatures and preliminary heating are required.

Also of interest is the recently discovered form of phosphorus - metallic. It is a conductor and has a cubic crystal lattice.

Chemical properties

The chemical properties of phosphorus depend on what form it is in. As mentioned above, the yellow and white modifications are the most active. In general, phosphorus is able to interact with:

• metals, forming phosphides and acting as an oxidizing agent;
• non-metals, acting as a reducing agent and forming volatile and non-volatile compounds of various kinds;
• strong oxidants, passing into phosphoric acid;
• with concentrated caustic alkalis by disproportionation type;
• with water at very high temperatures;
• with oxygen to form various oxides.

The chemical properties of phosphorus are similar to those of nitrogen. after all, he is part of the pnictogen group. However, the activity is several orders of magnitude higher due to the variety of allotropic modifications.

Being in nature

As a nutrient, phosphorus is very abundant. Its percentage in the earth's crust is 0.09%. This is a fairly large figure. Where is this atom found in nature? There are a few main places to mention:

• the green part of plants, their seeds and fruits;
• animal tissues (muscles, bones, tooth enamel, many important organic compounds);
• earth's crust;
• the soil;
• rocks and minerals;
• sea \u200b\u200bwater.

In this case, one can only talk about bound forms, but not about a simple substance. After all, he is extremely active, and this does not allow him to be free. Among the minerals, the richest in phosphorus are:

• english;
• fluoroapaptitis;
• svanbergite;
• phosphorite and others.

The biological significance of this element cannot be overestimated. After all, it is part of such compounds as:

• proteins;
• phospholipids;
• phosphoproteins;
• enzymes.

That is, all those that are vital and of which the whole organism is built. The daily allowance for an average adult is about 2 grams.

Phosphorus and its compounds

Being very active, this element forms many different substances. After all, it forms both phosphides, and itself acts as a reducing agent. Due to this, it is difficult to name an element that would be inert when reacting with it. Therefore, the formulas of phosphorus compounds are extremely diverse. There are several classes of substances in the formation of which he is an active participant.

1. Binary compounds - oxides, phosphides, volatile hydrogen compounds, sulfide, nitride and others. For example: R 2 O 5, PCL 3, P 2 S 3, PH 3 and others.
2. Complex substances: salts of all types (medium, acidic, basic, double, complex), acids. Example: H 3 PO 4, Na 3 PO 4, H 4 P 2 O 6, Ca (H 2 PO 4) 2, (NH 4) 2 HPO 4 and others.
3. Oxygen-containing organic compounds: proteins, phospholipids, ATP, DNA, RNA and others.

Most of the designated types of substances are of great industrial and biological importance. The use of phosphorus and its compounds is possible both for medical purposes and for the manufacture of quite ordinary household items.

Compounds with metals

Binary compounds of phosphorus with metals and less electronegative non-metals are called phosphides. These are salt-like substances that are extremely unstable when exposed to various agents. Even ordinary water causes rapid decomposition (hydrolysis).

In addition, under the action of non-concentrated acids, the substance also decomposes into the corresponding products. For example, if we talk about the hydrolysis of calcium phosphide, then the products will be metal hydroxide and phosphine:

Ca 3 P 2 + 6H 2 O \u003d 3Ca (OH) 2 + 2PH 3

And by subjecting phosphide to decomposition under the action of a mineral acid, we get the corresponding salt and phosphine:

Ca 3 P 2 + 6HCL \u003d 3CaCL 2 + 2PH 3

In general, the value of the compounds under consideration lies precisely in the fact that as a result, a hydrogen phosphorus compound is formed, the properties of which will be considered below.

Phosphorus-based volatiles

There are two main ones:

• white phosphorus;
• phosphine.

We already mentioned the first one above and gave the characteristics. They said that it was white thick smoke, highly poisonous, odorless and self-igniting under normal conditions.

But what is phosphine? This is the most common and well-known volatile substance, which contains the element in question. It is binary, and the second participant is hydrogen. The formula for the hydrogen compound of phosphorus is PH 3, the name is phosphine.

The properties of this substance can be described as follows.

1. Volatile colorless gas.
2. Very poisonous.
3. Has a rotten fish smell.
4. It does not interact with water and dissolves very poorly in it. Let's well dissolve in organic matter.
5. It is very chemically active under normal conditions.
6. Self-igniting in air.
7. Formed by the decomposition of metal phosphides.

Another name is phosphan. Stories from antiquity itself are associated with it. It's all about which sometimes people have seen and see now in cemeteries, swamps. Ball-shaped or candle-like lights that appear here and there, giving the impression of movement, were considered a bad omen and were very much feared by superstitious people. The reason for this phenomenon, according to the modern views of some scientists, can be considered spontaneous combustion of phosphine, which is formed naturally during the decomposition of organic residues, both plant and animal. The gas comes out and, in contact with atmospheric oxygen, ignites. Flame color and size may vary. Most often, these are greenish bright lights.

Obviously, all volatile phosphorus compounds are poisonous substances that can be easily detected by a strong unpleasant odor. This sign helps to avoid poisoning and unpleasant consequences.

Compounds with non-metals

If phosphorus behaves as a reducing agent, then we should talk about binary compounds with non-metals. Most often, they are the most electronegative. So, there are several types of substances of this kind:

• a compound of phosphorus and sulfur - phosphorus sulfide P 2 S 3;
• phosphorus chloride III, V;
• oxides and anhydride;
• bromide and iodide and others.

The chemistry of phosphorus and its compounds is diverse, so it is difficult to identify the most important ones. If we talk specifically about the substances that are formed by their phosphorus and non-metals, then oxides and chlorides of different compositions are of the greatest importance. They are used in chemical syntheses as dehydrating agents, as catalysts and so on.

So, one of the most powerful drying agents is the highest - P 2 O 5. It attracts water so strongly that upon direct contact with it, a violent reaction occurs with strong noise accompaniment. The substance itself is a white snow-like mass, in terms of its state of aggregation closer to amorphous.

It is known that organic chemistry by the number of compounds is much superior to inorganic. This is due to the phenomenon of isomerism and the ability of carbon atoms to form chains of atoms of various structures, closing with each other. Naturally, there is a certain order, that is, a classification that all organic chemistry is subject to. The classes of connections are different, however, we are interested in one specific one, directly related to the element in question. It's with phosphorus. These include:

• coenzymes - NADP, ATP, FMN, pyridoxal phosphate and others;
• proteins;
• nucleic acids, since the phosphoric acid residue is part of the nucleotide;
• phospholipids and phosphoproteins;
• enzymes and catalysts.

The type of ion in which phosphorus participates in the formation of the molecule of these compounds is the following - PO 4 3-, that is, it is an acidic residue of phosphoric acid. It is included in the composition of some proteins as a free atom or a simple ion.

For the normal functioning of each living organism, this element and the organic compounds formed by it are extremely important and necessary. Indeed, without protein molecules, it is impossible to build any structural part of the body. And DNA and RNA are the main carriers and transmitters of hereditary information. In general, all connections must be present without fail.

The use of phosphorus in industry

The use of phosphorus and its compounds in industry can be characterized in several points.

1. They are used in the production of matches, explosive compounds, incendiary bombs, certain types of fuel, lubricants.
2. As a gas absorber, as well as in the manufacture of incandescent lamps.
3. To protect metals from corrosion.
4. In agriculture as soil fertilizer.
5. As a water softener.
6. In chemical synthesis in the production of various substances.

The role in living organisms is reduced to participation in the formation of tooth enamel and bones. Participation in the reactions of ana- and catabolism, as well as maintaining the buffering of the internal environment of the cell and biological fluids. It is the basis for the synthesis of DNA, RNA, phospholipids.

Phosphorus was discovered in 1669 by the alchemist from Hamburg Hennig Brand, who experimented with the evaporation of human urine, trying to get the Philosopher's Stone. The substance formed after numerous manipulations turned out to be like wax, burned unusually brightly, with flickering. The new substance was named phosphorus mirabilis(from Latin miraculous carrier of fire). A few years later, phosphorus was obtained by Johann Kunkel, and also, independently of the first two scientists, by R. Boyle.

Phosphorus is an element of the XV group of the III period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 15 and atomic mass 30.974. The accepted designation is R.

Being in nature

Phosphorus is found in seawater and the earth's crust mainly in the form of minerals, of which there are about 190 (the most important are apatite and phosphorite). It is part of all parts of green plants, proteins, DNA.

phosphorus is a non-metal with high chemical activity; it practically does not occur in free form. There are four known phosphorus modifications - red, white, black and metallic.

Daily need for phosphorus

For normal functioning, the body of an adult must receive 1.0-2.0 g of phosphorus per day. For children and adolescents, the norm is 1.5-2.5 g, for pregnant and lactating women it increases to 3.0-3.8 g (calorizator). The daily requirement for phosphorus increases during regular sports training and physical activity.

The main suppliers of phosphorus are fish and seafood, cottage cheese, cheese, nuts, legumes and cereals. A sufficient amount of phosphorus contains and, and, berries, mushrooms and meat, and.

Signs of phosphorus deficiency

An insufficient amount of phosphorus in the body is characterized by fatigue and weakness, may be accompanied by loss of appetite and attention, frequent colds, anxiety and a sense of fear.

Signs of excess phosphorus

Signs of excess phosphorus in the body are bleeding and hemorrhage, anemia develops, and kidney stones occur.

Phosphorus ensures normal growth of bone and dental tissues of the body, maintains them in a healthy state, also participates in protein synthesis, plays an important role in the metabolism of fats, proteins and carbohydrates. Without phosphorus, muscles cannot function, and mental activity does not occur.

Phosphorus assimilation

When taking mineral complexes, it is worth remembering the best balance of phosphorus and (3: 2), and also that an excessive amount slows down the process of phosphorus absorption.

Phosphorus is widely used in industry and agriculture, primarily because of its flammability. It is used in the production of fuels, matches, explosives, phosphate fertilizers and the protection of metal surfaces from corrosion.

Forest-steppe soils

are characterized by the content in the humus substance in the amount of 1.78-2.46%.

Powerful black soil

contain 0.81-1.25% in the humus substance.

Ordinary chernozems

contain 0.90-1.27% in the humus substance.

Leached black soil

contain in the humic substance 1.10-1.43%.

Dark chestnut soils contain

in the humic substance 0.97-1.30%.

Role in the plant

Biochemical functions

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

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

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

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

Nucleic acids

Adenosine Phosphates

The special role of phosphorus in plant life is to participate in the energy metabolism of the plant cell. The main role in this process belongs to adenosine phosphates. They contain residues of phosphoric acid linked by high-energy bonds. When hydrolyzed, they are able to release a significant amount of energy.

They represent a kind of accumulator of energy, supplying it as needed for the implementation of all processes in the cell.

Distinguish between adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP). The latter, in terms of energy reserves, significantly exceeds the first two and takes a leading role in energy exchange. It consists of adenine (purine base) and sugar (ribose), as well as three phosphoric acid residues. ATP is synthesized 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, regulate the permeability of cell organelles and plasmalemma for various substances.

The cytoplasm of all plant cells contains a representative of the phosphatide group lecithin. It is a derivative of diglyceride phosphoric acid, a fat-like substance with a composition of 1.37%.

Sugar phosphates

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

Phytin

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

The main functions of phosphorus

Most of the 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 (reused).

Introduction

Phosphorus (Latin Phosphorus) P is a chemical element of group V of the periodic system of Mendeleev atomic number 15, atomic mass 30.973762 (4). Consider the structure of the phosphorus atom. There are five electrons on the outer energy level of the phosphorus atom. 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 capable of glowing.

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

Fertilizers contain many phosphorus-containing substances. 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 oxidizability, phosphorus is found in nature only in the form of compounds. The main phosphorus minerals are phosphorites and apatites, of the latter, fluorapatite 3Ca 3 (PO 4) 2 * CaF 2 is the most widespread. Phosphorites are widespread in the Urals, the Volga region, Siberia, Kazakhstan, Estonia, and Belarus. The largest deposits of apatite are located on the Kola Peninsula.

Phosphorus is an essential 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 body of an adult 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, purple phosphorus, etc. The first three of these are the most studied.

White phosphorus - colorless, with a yellowish tinge crystalline substance, glowing in the dark. Its density is 1.83 g / cm 3. It does not dissolve in water, it dissolves well in carbon disulfide. Has a characteristic garlic smell. Melting point 44 ° С, autoignition temperature 40 ° С. To protect white phosphorus from oxidation, it is stored under water in the dark (it transforms into red phosphorus in the light). In the cold, white phosphorus is fragile, at temperatures above 15 ° C it becomes soft and is cut with a knife.

Molecules of white phosphorus have a crystal lattice, in the nodes of which there are P 4 molecules in the form of a tetrahedron.

Each phosphorus atom is bonded by three β-bonds to the other three atoms.

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

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

Black phosphorussimilar in appearance to graphite, greasy to the touch, has semiconducting properties. Density 2.7 g / cm 3.

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 \u003d 2PCl 3 (phosphorus (III) chloride),

PCl 3 + Cl 2 \u003d PCl 5 (phosphorus (V) chloride).

2. Interaction with nematals:

2P + 3S \u003d P 2 S 3 (phosphorus (III) sulfide.

3. Interaction with metals:

2P + 3Ca \u003d Ca 3 P 2 (calcium phosphide).

4. Interaction with oxygen:

4P + 5O 2 \u003d 2P 2 O 5 (phosphorus (V) oxide, phosphoric anhydride).

II. Interaction with complex substances.

3P + 5HNO 3 + 2H 2 O \u003d 3H 3 PO 4 + 5NO ^.

Receiving

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 vapors, which condense in a receiver underwater to form 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 pressures (200 ° C and 1200 MPa).

Application

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

The resulting oxygen contributes to the ignition of the match head.

Phosphorus is used in metallurgy. It is used to obtain conductors and is part 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, as it produces white smoke when it burns.

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. Receiving

1.5. Application

Chapter II. Phosphorus compounds

2.1. Oxides

2.2. Acids and their salts

2.3. Phosphine

Chapter III. Phosphate fertilizers

Conclusion

Bibliographic list

Introduction

Phosphorus (Latin Phosphorus) P is a chemical element of group V of Mendeleev's periodic table atomic number 15, atomic mass 30.973762 (4). Consider the structure of the phosphorus atom. There are five electrons on the outer energy level of the phosphorus atom. 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 transforming base metals into gold, when evaporating urine with coal and sand, isolated a white waxy substance capable of glowing.

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

Fertilizers contain many phosphorus-containing substances. 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 oxidizability, phosphorus is found in nature only in the form of compounds. The main phosphorus minerals are phosphorites and apatites; of the latter, fluorapatite 3Ca 3 (PO 4) 2 CaF 2 is the most widespread. Phosphorites are widespread in the Urals, the Volga region, Siberia, Kazakhstan, Estonia, and Belarus. The largest deposits of apatite are located on the Kola Peninsula.

Phosphorus is an essential 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 body of an adult 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, purple phosphorus, etc. The first three of these are the most studied.

White phosphorus - colorless, with a yellowish tinge crystalline substance, glowing in the dark. Its density is 1.83 g / cm 3. It does not dissolve in water, it dissolves well in carbon disulfide. Has a characteristic garlic smell. Melting point 44 ° С, autoignition temperature 40 ° С. To protect white phosphorus from oxidation, it is stored under water in the dark (it transforms into red phosphorus in the light). In the cold, white phosphorus is fragile, at temperatures above 15 ° C it becomes soft and is cut with a knife.

Molecules of white phosphorus have a crystal lattice, in the nodes of which there are P 4 molecules in the form of a tetrahedron.

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

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

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

Black phosphorus similar in appearance to graphite, greasy to the touch, has semiconducting properties. Density 2.7 g / cm 3.

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 + 3Cl 2 \u003d 2PCl 3 (phosphorus (III) chloride),

PCl 3 + Cl 2 \u003d PCl 5 (phosphorus (V) chloride).

2. Interaction with nematals:

2P + 3S \u003d P 2 S 3 (phosphorus (III) sulfide.

3. Interaction with metals:

2P + 3Ca \u003d Ca 3 P 2 (calcium phosphide).

4. Interaction with oxygen:

4P + 5O 2 \u003d 2P 2 O 5 (phosphorus (V) oxide, phosphoric anhydride).

II. Interaction with complex substances.

3P + 5HNO 3 + 2H 2 O \u003d 3H 3 PO 4 + 5NO.

1.4 Obtaining

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 vapors, which condense in a receiver underwater to form 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 pressures (200 ° C and 1200 MPa).

1.5 Application

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

KCl +.

The resulting oxygen contributes to the ignition of the match head.

Phosphorus is used in metallurgy. It is used to obtain conductors and is part 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, as it produces white smoke when it burns.

Chapter II ... Phosphorus compounds

2.1 Oxides

Phosphorus forms several oxides. The most important of them are phosphorus (V) oxide P 4 O 10 and phosphorus (III) oxide P 4 O 6. Often their formulas are written in a simplified form - P 2 O 5 and P 2 O 3. The structure of these oxides retains the tetrahedral arrangement of phosphorus atoms.

Phosphorus oxide (III) P 4 O 6 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:

P 4 O 6 + 6H 2 O \u003d 4H 3 PO 3,

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

Strong reducing agent. When interacting with oxygen, it is oxidized to P 4 O 10.

Phosphorus (III) oxide is obtained by oxidation of white phosphorus with a lack of oxygen.

Phosphorus oxide (V) P 4 O 10 is a white crystalline powder. The sublimation temperature is 36 ° C. It has several modifications, one of which (the so-called volatile) has a composition of P 4 O 10. The crystal lattice of this modification is composed of P 4 O 10 molecules, interconnected by weak intermolecular forces, which are easily torn apart when heated. Hence the volatility of this species. Other modifications are polymeric. They are formed by endless layers of PO 4 tetrahedra.

When P 4 O 10 interacts with water, phosphoric acid is formed:

P 4 O 10 + 6H 2 O \u003d 4H 3 PO 4.

As an acidic oxide, P 4 O 10 reacts with basic oxides and hydroxides.

It is formed during high-temperature oxidation of phosphorus in excess of 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 terms of its drying effect, it surpasses all other substances. It takes away chemically bound water from anhydrous perchloric acid to form its anhydride:

4HClO 4 + P 4 O 10 \u003d (HPO 3) 4 + 2Cl 2 O 7.

2.2 Acids and their salts

and) Phosphorous acid H 3 PO 3. Anhydrous phosphorous acid H 3 PO 3 forms crystals with a density of 1.65 g / cm 3, melting at 74 ° C.

Structural formula:

.

When anhydrous H 3 PO 3 is heated, a disproportionation reaction (self-oxidation-self-healing) occurs:

4H 3 PO 3 \u003d PH 3 + 3H 3 PO 4.

Phosphorous acid salts - phosphites ... For example, K 3 PO 3 (potassium phosphite) or Mg 3 (PO 3) 2 (magnesium phosphite).

Phosphorous acid H 3 PO 3 is obtained by dissolving phosphorus (III) oxide in water or by hydrolysis of phosphorus (III) chloride РCl 3:

РCl 3 + 3H 2 O \u003d H 3 PO 3 + 3HCl.

b) Phosphoric acid (orthophosphoric acid) H 3 PO 4.

Anhydrous phosphoric acid is a light transparent crystals that spread in air at room temperature. Melting point 42.35 ° C. With water, phosphoric acid forms solutions of any concentration.