What are allotropic modifications of phosphorus. Allotropic modifications of phosphorus

Phosphorus forms several allotropic modifications- modifications. The phenomenon of allotropic modifications in phosphorus is caused by the formation of various crystalline forms. White phosphorus (P4) has a molecular crystal lattice, red and black - atomic. The difference in the structure of the crystal lattice determines the difference in their physical and chemical properties. White phosphorus - strong poison, even in small doses, it is deadly. In the solid state, it is obtained with rapid cooling phosphorus vapor. In its pure form, it is completely colorless, transparent, appearance similar to wax: brittle in the cold, at temperatures above 15 ° C - soft, easy to cut with a knife; insoluble in water, but readily soluble in carbon disulfide - CS2 and in organic solvents; easy to melt, volatile. The strength of the bond in the molecule is low, which is the reason for the high chemical activity. White phosphorus quickly oxidizes in air, while glowing in the dark - the conversion of chemical energy into light; spontaneously ignites in air, with slight heating, slight friction. It reacts with oxygen without ignition, even under water, forming first Р2О3, then P2O5 :

With prolonged heating, white phosphorus turns into red. White phosphorus is used for the manufacture of ammunition for artillery shells, air bombs, designed to form smoke screens. Has no wide application.

Red phosphorus - red-brown powder, non-toxic, non-volatile, insoluble in water and in many organic solvents and carbon disulfide; does not ignite in air and does not glow in the dark. It ignites only when heated to 260 °C. With strong heating, without air access, without melting (bypassing liquid state) evaporates - sublimes. When cooled, it turns into white phosphorus. It is used for the manufacture of matches: red phosphorus mixed with antimony sulfide, red lead, with an admixture of quartz and glue is applied to the surface matchbox. The head of a match consists mainly of Berthollet salt, ground glass, sulfur and glue. When the head is rubbed against the plaster of the box, red phosphorus ignites, sets fire to the composition of the head, and the tree lights up from it. Red phosphorus is also used in the preparation of pharmaceutical preparations.

black phosphorus produced by high heat and high pressure white phosphorus. Black phosphorus is heavier than other modifications. It is used very rarely - as a semiconductor in the composition of gallium and indium phosphate in metallurgy.

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Phosphorus forms several allotropic modifications - modifications. The phenomenon of allotropic modifications in phosphorus is caused by the formation of various crystalline forms. White phosphorus (P4) has a molecular crystal lattice, red and black - atomic. The difference in the structure of the crystal lattice also determines the difference in their physical and chemical properties. White phosphorus - strong poison, even in small doses, it is deadly. In the solid state, it is obtained by rapid cooling of phosphorus vapor. In its pure form, it is completely colorless, transparent, similar in appearance to wax: in the cold it is brittle, at temperatures above 15 ° C it is soft, easily cut with a knife; insoluble in water, but readily soluble in carbon disulfide - CS2 and in organic solvents; easy to melt, volatile. The strength of the bond in the molecule is low, which is the reason for the high chemical activity. White phosphorus quickly oxidizes in air, while glowing in the dark - the conversion of chemical energy into light; spontaneously ignites in air, with slight heating, slight friction. It reacts with oxygen without ignition, even under water, forming first Р2О3, then P2O5:

Red phosphorus - red-brown powder, non-toxic, non-volatile, insoluble in water and in many organic solvents and carbon disulfide; does not ignite in air and does not glow in the dark. It ignites only when heated to 260 °C. With strong heating, without access to air, without melting (bypassing the liquid state), it evaporates - sublimes. When cooled, it turns into white phosphorus. It is used for the manufacture of matches: red phosphorus mixed with antimony sulfide, iron minium, with an admixture of quartz and glue is applied to the surface of a matchbox. The head of a match consists mainly of Berthollet salt, ground glass, sulfur and glue. When the head is rubbed against the plaster of the box, red phosphorus ignites, sets fire to the composition of the head, and the tree lights up from it. Red phosphorus is also used in the preparation of pharmaceutical preparations.

black phosphorus obtained by strong heating and high pressure of white phosphorus. Black phosphorus is heavier than other modifications. It is used very rarely - as a semiconductor in the composition of gallium and indium phosphate in metallurgy.

36. Phosphorus oxides and phosphoric acids

The element phosphorus forms a number of oxides, the most important being phosphorus(III) oxide. P2O3 and phosphorus(V) oxide P2O5.

Phosphorus (III) oxide, or phosphorous anhydride (P2O3) obtained by the slow oxidation of phosphorus, burning it in a lack of oxygen. It is a waxy, crystalline white mass with a melting point of 22.5 °C. Poisonous.

Chemical properties:

1) reacts with cold water, forming phosphorous acid H3PO3;

2) interacting with alkalis, forms salts - phosphites;

3) is a strong reducing agent.

Interacting with oxygen, it is oxidized to phosphorus (V) oxide P2O5.

Phosphorus (V) oxide, or phosphoric anhydride(P2O5) obtained by burning phosphorus in air or oxygen. It is a white crystalline powder with a melting point of 36 °C.

Chemical properties:

1) interacting with water, forms ortho-phosphoric acid H3PO4;

2) having properties acid oxide, reacts with basic oxides and hydroxides;

3) capable of absorbing water vapor.

Phosphoric acids.

Phosphoric anhydride corresponds to several acids. The main one is phosphoric acid H3PO4. Anhydrous phosphoric acid is presented in the form of colorless transparent crystals with a melting point of 42.35 ° C and readily soluble in water.

Forms three types of salts:

1) medium salts - orthophosphates;

2) acidic salts with one hydrogen atom;

3) acidic salts with two hydrogen atoms.

Getting phosphoric acid:

1) in the laboratory: 3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO?;

2) in industry: a) thermal method; b) extraction method: Ca3(PO4)2 + 3H2SO4 = CaSO4? + 2 H3PO4.

Natural phosphates are reduced to free phosphorus, which is burned in air or oxygen. The reaction product is dissolved in water.

The remaining phosphoric acids, depending on the method of connecting the PO4 groups, form 2 types of acids: polyphosphoric acids, which consist of chains - PO3-O-PO3-... and metaphosphoric acids, which consist of rings formed by PO4.

Application: orthophosphoric acid is used in the production of fertilizers, chemical reagents, organic compounds, and for the preparation of protective coatings on metals. Phosphates are used in the production of enamels and pharmaceuticals. Metaphosphates are part of detergents.

Phosphorus forms several allotropic modifications - modifications. The phenomenon of allotropic modifications in phosphorus is caused by the formation of various crystalline forms. White phosphorus (P4) has a molecular crystal lattice, red and black - atomic. The difference in the structure of the crystal lattice also determines the difference in their physical and chemical properties. White phosphorus - strong poison, even in small doses, it is deadly. In the solid state, it is obtained by rapid cooling of phosphorus vapor. In its pure form, it is completely colorless, transparent, similar in appearance to wax: in the cold it is brittle, at temperatures above 15 ° C it is soft, easily cut with a knife; insoluble in water, but readily soluble in carbon disulfide - CS2 and in organic solvents; easy to melt, volatile. The strength of the bond in the molecule is low, which is the reason for the high chemical activity. White phosphorus quickly oxidizes in air, while glowing in the dark - the conversion of chemical energy into light; spontaneously ignites in air, with slight heating, slight friction. It reacts with oxygen without ignition, even under water, forming first Р2О3, then P2O5:

Red phosphorus - red-brown powder, non-toxic, non-volatile, insoluble in water and in many organic solvents and carbon disulfide; does not ignite in air and does not glow in the dark. It ignites only when heated to 260 °C. With strong heating, without access to air, without melting (bypassing the liquid state), it evaporates - sublimes. When cooled, it turns into white phosphorus. It is used for the manufacture of matches: red phosphorus mixed with antimony sulfide, iron minium, with an admixture of quartz and glue is applied to the surface of a matchbox. The head of a match consists mainly of Berthollet salt, ground glass, sulfur and glue. When the head is rubbed against the plaster of the box, red phosphorus ignites, sets fire to the composition of the head, and the tree lights up from it. Red phosphorus is also used in the preparation of pharmaceutical preparations.

36. Phosphorus oxides and phosphoric acids

The element phosphorus forms a number of oxides, the most important being phosphorus(III) oxide. P2O3 and phosphorus(V) oxide P2O5.

Chemical properties:

1) reacts with cold water, forming phosphorous acid H3PO3;

2) interacting with alkalis, forms salts - phosphites;

3) is a strong reducing agent.

Interacting with oxygen, it is oxidized to phosphorus (V) oxide P2O5.

Phosphorus oxide (V), or phosphoric anhydride (P2O5) obtained by burning phosphorus in air or oxygen. It is a white crystalline powder with a melting point of 36 °C.

Chemical properties:

1) interacting with water, forms ortho-phosphoric acid H3PO4;

2) having the properties of an acidic oxide, it reacts with basic oxides and hydroxides;

3) capable of absorbing water vapor.

Phosphoric acids.

Forms three types of salts:

1) medium salts - orthophosphates;

2) acidic salts with one hydrogen atom;

3) acidic salts with two hydrogen atoms.

Getting phosphoric acid:

1) in the laboratory: 3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO?;

2) in industry: a) thermal method; b) extraction method: Ca3(PO4)2 + 3H2SO4 = CaSO4? + 2 H3PO4.

Natural phosphates are reduced to free phosphorus, which is burned in air or oxygen. The reaction product is dissolved in water.