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Phosphorus, atomic structure, allotropy, chemical properties of phosphorus. Phosphorus(V) oxide

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1. To study the physical and chemical properties of phosphorus, phosphorus oxide. To fix the concept of allotropy on the example of allotropic modifications of phosphorus. 3. To develop interest in the subject, the formation of a dialectical-materialistic worldview of students, considering the phosphorus cycle in nature. 2. To promote the development of students' ability to analyze, generalize, systematize the knowledge gained.

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1 Discovery of phosphorus (1669 - German chemist H. Brand). 2. The structure of the phosphorus atom. 3. Being in nature. 4. Physical properties. Allotropic modifications of phosphorus. 5. Chemical properties phosphorus. Redox duality. 6. Phosphorus(V) oxide, physical and chemical properties. 7. biological significance phosphorus. Phosphorus cycle in nature. The use of phosphorus and its compounds.

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Phosphorus (Phosphorus, from the Greek. Phoros - carrying light). Former German soldier and later alchemist Hoenig Brand decided to get rich. He wandered around the city of Hamburg in search of a way to improve his affairs, and in a pub he met an alchemist who told him that there was a certain "philosopher's stone" that turns iron and lead into gold. But one must look for this stone in the human body and in what comes from it, for example, in urine ... Shaken by what he heard, Brand secretly collected this "human product" in the soldiers' barracks and evaporated it in portions. He combined the dry remains and, calcining them with coal, suddenly saw white smoke in the vessel, glowing in the dark. So in 1669, white phosphorus was obtained - the first non-metal, the discovery of which is documented and has a certain date.

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Phosphorus is one of the most abundant elements in earth's crust(0.093% by mass). Phosphorus does not occur in the free state in nature due to its high chemical activity. In bound form, it is included in about 200 minerals, mainly apatites Ca3(PO4)2*CaCl2 (chlorapatite), Ca3(PO4)2*CaF2 (fluorapatite), and also phosphorites Ca3(PO4)2. Large reserves of apatite are located on the Kola Peninsula. Phosphorus is found in plant and animal proteins. The content of phosphorus in the brain tissues is 0.38%, in the muscles 0.27%. fluorapatite phosphorite chlorapatite

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Black phosphorus Red phosphorus White phosphorus Phosphorus forms several allotropic modifications. The main ones are white, red and black phosphorus. White phosphorus is a crystalline powder, has a molecular crystal lattice. It is insoluble in water, but soluble in organic solvents, volatile. White phosphorus is a strong poison. Under normal conditions, it is oxidized by atmospheric oxygen, the oxidation of phosphorus is accompanied by a glow, which is clearly visible in the dark. Red phosphorus is a dark red powder, it is non-toxic, non-volatile. It interacts with oxygen only when ignited. It has an atomic crystal lattice. At a pressure of 12∙108 Pa, it transforms into black phosphorus. Black phosphorus is formed from white at high pressure. By appearance it looks like graphite, has an atomic crystal lattice, and has semiconductor properties.

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Chemical properties of phosphorus B chemical reactions Phosphorus exhibits redox duality. Phosphorus interacts with metals, halogens, sulfur, oxygen. (These reaction equations will be offered for students to complete in homework) With oxidizing salts, phosphorus reacts with a strong explosion, which can lead to an accident, it must not be mixed with Berthollet salt: 6P + 5KCIO3 → 3 P2O5 + 5KCI This reaction is used in the manufacture of matches. Make diagrams of the electronic balance of these reactions. 2P0+3Ca0=Ca3+2P2–3 oxidizing agent reducing agent 4P0+5O20=2P2+5O5–2 reducing agent oxidizing agent oxidizing agent reducing agent P+Ca→Ca3P2 P+O2→P2O5 oxidizing agent reducing agent P+Ca→Ca3P2 P+O2→P2O5 P+3e– ®P–3 2 Ca-2e–®Ca+2 3 P0-5e–®P+5 4 O20+4e–®2O–2 5

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Phosphorus oxide (V) P2O5 is a white crystalline substance. It cannot be obtained by dehydration of phosphoric acid due to the high exothermicity of its reaction with water. This is the basis of its practical application as a dehumidifier. It reacts with water when heated to form phosphoric acid. Phosphorus oxide (V) Р2О5 Draw your own conclusion about the nature of this oxide, choose the equations of possible reactions characteristic of it: Phosphorus oxide (V) reacts with: a) water, b) potassium hydroxide c) carbon monoxide (ΙV) d) iron e ) barium oxide Write the equations of possible reactions in your notebook.

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Phosphorus compounds are an essential component of plants, animals, and humans. In plants, phosphorus is found mainly in seeds, fruits: In humans and animals, in the skeleton, muscle, and nervous tissue.

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Plants absorb the phosphorus they need from the soil. Animals get it with plant foods. After the death of plants and animals, organic phosphorus-containing compounds are converted into inorganic phosphates under the influence of phosphorobacteria. The lack of phosphorus in the soil is not replenished naturally, so it is necessary to apply phosphorus-containing fertilizers to the soil.

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A1 Electronic configuration 1S22S22P63S23P6 corresponds to the particle: 1) Р+3 2) Р-3 3) Р+5 4) N-3

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A2 Which of the following substances does not react with phosphorus oxide (V): water calcium oxide sodium hydroxide 4) sulfur oxide (VΙ)

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A3 Which of the following statements are correct: A Phosphorus forms several allotropic modifications: white, red and black B All allotropic modifications of phosphorus have atomic crystal lattices 2) Only B is true 3) Both statements are true 4) Both statements are false Only A is true

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Synopsis of a chemistry lesson in grade 9 on the topic:

"Phosphorus. The structure of the atom, allotropy, properties and applications of phosphorus" with a presentation

Lesson topic: "Phosphorus. The structure of the atom, allotropy, properties and uses of phosphorus.

The purpose of the lesson: Determine the position of phosphorus in the periodic system of chemical elements D.I. Mendeleev, to consider the structure of the phosphorus atom, the physical and chemical properties, the fields of application of phosphorus.

Lesson objectives:

Educational:

1. Consider the structure of the phosphorus atom according to its position in the periodic system of chemical elements D.I. Mendeleev, allotropic modifications of phosphorus.
2. To study the physical and chemical properties of phosphorus, its presence in nature, its fields of application.
3. To continue the formation of students' ability to work with the periodic system of chemical elements of D. I. Mendeleev.
4. Improve the ability to write equations of chemical reactions.

Developing:

1. Develop the memory and attention of students.
2. To form a positive motivation for studying the subject of chemistry.
3. Learn to apply existing knowledge in a new situation.

Educational:

1. Show significance chemical knowledge for modern man.

Equipment:

PSHE, computer, multimedia projector, electronic manual "Video demonstrations".

Lesson type:

Combined. A lesson in learning new material.

Forms of organization of educational activities:

1. independent work with the text of the textbook;
2. frontal;
3. student messages (individual);
4. work in groups.

Teaching methods. Methods of organizing educational activities:

1. verbal (heuristic conversation),
2. visual (collection, video clip) based on cognitive activity
3. partial search;

Pedagogical techniques:

1. educational and organizational (determining the purpose and objectives of the lesson, creating favorable conditions for activity);
2. educational - informational (conversation, statement of the problem, its discussion, work with the textbook, observation);
3. educational and intellectual (perception, comprehension, memorization of information, problem solving, activity motivation).

During the classes.

I. Organizational moment.

The psychological mood of students, checking readiness for the lesson.

The teacher greets the students.

II. Knowledge update (slide 2.)

Yes! It was a dog, huge, pitch black. But none of us mortals have ever seen such a dog. Flames shot out of her open mouth, sparks flew from her eyes, flickering fire poured over her muzzle and nape. In no one's inflamed brain could a vision more terrible, more disgusting than this hellish creature that jumped out of the fog at us ... A terrible dog, the size of a young lioness. Its huge maw still glowed with bluish flames, its deep-set wild eyes circled in fiery circles.

I touched this luminous head and, taking my hand away, saw that my fingers also glowed in the darkness. Phosphorus, I said.

Arthur Conan Doyle. "The Hound of the Baskervilles"

This is the bad story in which element N 15 turned out to be involved

So, the topic of the lesson is “Phosphorus. The structure of the atom, allotropy, properties and use of phosphorus "the purpose and objectives of the lesson (slides 3, 4)

III. Learning new material.

1. The position of phosphorus in the periodic table of chemical elements (slide 5, 6)

Task: Using the periodic table of chemical elements, characterize the chemical elements of phosphorus and nitrogen, fill in the table.

Option 1 - the position in the PSCE and the structure of the nitrogen atom.

Option 2 - the position in the PSCE and the structure of the phosphorus atom.

Find similarities, differences between the structure of the nitrogen and phosphorus atom.

Conclusion: Both elements are in the main subgroup of group V of the PSCE, on the last energy level 5 electrons each, have same values lower oxidation states -3 (if they exhibit oxidizing properties, for example, with metals, hydrogen) and +5 in oxygen-containing compounds.

2. The valence state of the phosphorus atom (slide 7) - the teacher's explanation.

3. Being in nature (slide 8) - work with a textbook.

Class task:

In what form is phosphorus found in nature?

Laboratory experience No. 1.

1. Consider samples of minerals containing phosphorus.
2. Write down the names and formulas of the proposed minerals in a notebook.

4. Physical properties

Allotropic modifications of phosphorus (slide 9.10) - teacher's explanations

A) white phosphorus (slide 11.12);

B) red phosphorus (slide 13.14);

C) black phosphorus (slide 15.16);

Conclusion: Three allotropic modifications - white, red, black.

5. Chemical properties of phosphorus (sweat 17)

1) The interaction of phosphorus with simple substances:

A) with metals, forming phosphides.

For example, the interaction of white phosphorus with calcium.

Task: Write down the reaction equation, make the electronic balance equation.

B) The interaction of phosphorus with non-metals.

For example: Interaction of phosphorus and oxygen (video clip).

Exercise:

1. Write down the reaction equations, make an electronic balance equation.
2. How does phosphorus burn in air and in oxygen?

C) The interaction of phosphorus with complex substances(potassium chlorate) (slide 18)

6P + 5KClO3 → 5KCl + 3P2O5

6. The use of phosphorus (slide 19) - student's performance.

III. Consolidation of the studied material (frontal survey):

1. Describe the position of phosphorus in the periodic table of chemical elements D.I. Mendeleev.

2. In what compound does phosphorus show an oxidation state of -3? (slide 20)

A) H3PO4

B) RN3

B) HPO3

3. In what form is phosphorus found in nature? Describe physical properties phosphorus (red, white, black).

4. With what substance does phosphorus react to form phosphide:

A) water

B) hydrogen

B) magnesium

IV. Homework (slide 23): § 22, ex. 3

V. Reflection

1. What new did you learn in the lesson?
2. What part of the lesson did you like?
3. What is your impression of the lesson?

VI. Summing up and conclusions of the lesson.

DEFINITION

Phosphorus located in the third period of group V of the main (A) subgroup of the Periodic Table.

Relates to elements p-families. Non-metal. Designation - P. Ordinal number - 15. Relative atomic mass - 30.974 a.m.u.

The electronic structure of the phosphorus atom

The phosphorus atom consists of a positively charged nucleus (+15), inside which there are 15 protons and 16 neutrons, and 15 electrons move around in three orbits.

Fig.1. Schematic structure of the phosphorus atom.

The distribution of electrons in orbitals is as follows:

15 P) 2) 8) 5 ;

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

The outer energy level of the phosphorus atom contains 5 electrons, which are valence. The energy diagram of the ground state takes the following form:

Each valence electron of a phosphorus atom can be characterized by a set of four quantum numbers: n(chief quantum), l(orbital), m l(magnetic) and s(spin):

sublevel

The presence of three unpaired electrons indicates that the oxidation state of phosphorus is +3. Since the third level has vacant orbitals 3 d-sublevel, then the phosphorus atom is characterized by the presence of an excited state:

That is why phosphorus also has an oxidation state of +5.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	The element consists of two isotopes in a ratio of 2:3. The nucleus of the first isotope contains 10 protons and 10 neutrons. Determine the atomic mass of the second isotope if the average relative mass of the element is 21.2. In your answer, indicate how many more neutrons are in the nucleus of an atom of the second isotope.
Decision	The relative atomic mass of the first isotope is: A 1 \u003d Z + n \u003d 10 + 10 \u003d 20 amu The relative atomic mass of the second isotope will be denoted by A 2 . The average relative atomic mass of an element is determined by the sum of the masses of its isotopes, taking into account their number. Let's make an equation: A cf ×5 = A 1 ×2 + A 2 ×3; 21.5 × 5 = 20 × 2 + A 2 × 3; A 2 = 22 amu There are 10 protons in the nucleus of the atom of the second isotope, therefore, the number of neutrons will be equal to n = A-Z =.22 - 10 = 12. According to the condition of the problem, there were 10 neutrons in the nucleus of the atom of the first isotope. This means that the nucleus of an atom of the second isotope contains two more neutrons than the nucleus of the first isotope.
Answer	The relative atomic mass of the second isotope is 22 amu.

Introduction

Phosphorus (lat. Phosphorus) P - a chemical element of group V periodic system Mendeleev atomic number 15, atomic mass 30.973762(4). Consider the structure of the phosphorus atom. There are five electrons in 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 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 compounds of phosphorus include oxides, acids and their salts (phosphates, dihydrophosphates, hydrophosphates, phosphides, phosphites).

A lot of substances containing phosphorus are found in fertilizers. Such fertilizers are called phosphate 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 occurs in nature only in the form of compounds. The main minerals of phosphorus are phosphorites and apatites, of the latter, fluorapatite 3Ca 3 (PO 4) 2 * CaF 2 is the most common. Phosphorites are widely distributed in the Urals, the Volga region, Siberia, Kazakhstan, Estonia, 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. Molecules of ATP - adenosine triphosphoric acid (ATP - collector and carrier of energy) are built from phosphorus. 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 P. 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 crystalline substance that glows in the dark. Its density is 1.83 g/cm3. Insoluble in water, soluble in carbon disulfide. It has a characteristic garlic odor. Melting point 44°C, self-ignition temperature 40°C. To protect white phosphorus from oxidation, it is stored under water in the dark (there is a transformation into red phosphorus in the light). In the cold, white phosphorus is brittle, at temperatures above 15°C it becomes soft and can be cut with a knife.

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

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

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

red phosphorus- powdery substance of dark red color, odorless, 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 that differ in color (from scarlet to purple). The properties of red phosphorus depend on the conditions for its preparation. Not poisonous.

black phosphorus similar in appearance to graphite, greasy to the touch, has semiconductor 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.

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 + 5HNO 3 + 2H 2 O \u003d 3H 3 PO 4 + 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 vapors, which condense in the receiver under water, forming white phosphorus.

When heated to 250-300°C in the absence of air, white phosphorus turns 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 figure). It is part of the mixture applied to the side surface of the matchbox. The main component of the composition of the match head is Bertolet's salt KClO 3 . From the friction of the match head on the spread, the phosphorus particles ignite in air. As a result of the oxidation reaction of phosphorus, heat is released, leading to the decomposition of 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, since it produces white smoke when it burns.

1Photo
2. Allotropy - the existence of two or more simple substances of the same chemical element, different in structure and properties - the so-called allotropic modifications or forms.
White phosphorus is a yellowish-white substance (due to impurities, it resembles wax in softness. A very active substance; it glows because it is oxidized by oxygen from the air already at room temperature. Very poisonous and smelly substance.
Yellow porsphorus is simply unrefined white porsphorus. Color - from yellow to brown. Just as active, just like white phosphorus, it ignites spontaneously in air.
Red phosphorus is a less active substance than white or yellow phosphorus, less soluble in water, does not self-ignite and does not glow in air. Less poisonous.
Black phosphorus is a black substance with a metallic sheen, greasy to the touch, very similar in appearance to graphite. Black phosphorus even conducts electricity, which is usually the case with metals. At a certain pressure, it can go into a modification, which is called metal phosphorus.
3. The most common is white phosphorus - it has a waxy structure and high toxicity. The melting point of this substance is forty-four degrees Celsius, and the boiling point is two hundred and eighty degrees. When this material is rubbed, it ignites very quickly, so they cut it only by placing it in an aquatic environment. If you heat it for a long time at a temperature of two hundred and fifty degrees Celsius, it turns into red phosphorus. This substance is presented in the form of a brown-red powder. Red phosphorus, unlike white, is not poisonous. The most stable form of existence of this element can be called black phosphorus, which, according to some external features, is similar to metal: it has a peculiar luster, has high hardness, electrical and thermal conductivity.
4. The chemical properties of phosphorus are largely determined by its allotropic modification. White phosphorus is very active, in the process of transition to red and black phosphorus, chemical activity decreases. White phosphorus in the air, when oxidized by atmospheric oxygen at room temperature, emits visible light, the glow is due to the photoemission reaction of phosphorus oxidation. 1) Phosphorus is easily oxidized by oxygen.
2) Interacts with many simple substances - halogens, sulfur, some metals, showing oxidizing and reducing properties, with metals - an oxidizing agent, forms phosphides.
3) Strong oxidizing agents convert phosphorus to phosphoric acid.
4) It interacts with water vapor at temperatures above 500 ° C, a disproportionation reaction proceeds with the formation of phosphine and phosphoric acid: 8P + 12H2O➡5PH3 + 3H3PO4.
5. Phosphorus is obtained from apatites or phosphorites as a result of interaction with coke and silica at a temperature of about 1600 ° C:
2Ca3+(PO4)2+10C+6SiO2➡P4+10CO+6CaSi3.
6. Red phosphorus is the main modification produced and consumed by industry. It is used in the manufacture of matches, explosives, incendiary compositions, various types fuel, as well as extreme pressure lubricants, as a getter in the production of incandescent lamps.
7. Phosphorus is present in living cells in the form of ortho- and pyrophosphoric acids, it is part of nucleotides, nucleic acids, phosphoproteins, phospholipids, coenzymes, enzymes. Human bones consist of hydroxylapatite 3Са3(PO4)3·Ca(OH)2. The composition of tooth enamel includes fluorapati. The exchange of phosphorus compounds is regulated by hormones and vitamin D. With a lack of phosphorus, various bone diseases develop in the body.