As you already know from the 8th grade chemistry course, most chemical elements are classified as metals (Fig. 24 and 25).

Rice. 24.
The position of the chemical elements-metals in the Periodic system of D. I. Mendeleev (short-period version)

In the Periodic system of D. I. Mendeleev, each period, except for the first (it includes two non-metal elements - hydrogen and helium), begins with an active chemical element-metal. These elements form the main subgroup of group I (IA group) and are called alkali metals. They got their name from the name of their corresponding hydroxides, which are highly soluble in water - alkalis.

Rice. 25.
The position of the chemical elements-metals in the Periodic system of D. I. Mendeleev (long-period version)

Alkali metal atoms contain only one electron at the external energy level, which they easily donate during chemical interactions, therefore they are the strongest reducing agents. It is clear that, in accordance with the increase in the radius of the atom, the reducing properties of alkali metals increase from lithium to francium.

Following the alkali metals, the elements that make up the main subgroup of group II (group IIA) are also typical metals with a strong reducing ability (their atoms contain two electrons at the external level). Of these metals, calcium, strontium and barium are called alkaline earth metals. These metals got such a name because their oxides, which in ancient times were called “earths” in Rus', form alkalis when dissolved in water.

Metals also include chemical elements of the main subgroup of group III (group IIIA), excluding boron.

Of the elements of the main subgroups of the following groups, metals include: in the IVA group - germanium *, tin, lead (the first two elements are carbon and silicon - non-metals), in the VA group - antimony and bismuth (the first three elements are non-metals), in the VIA group only the last element - polonium - is a pronounced metal. In the main subgroups of groups VIIA and VIIIA, all elements are typical non-metals.

* Germanium also exhibits some non-metallic properties, occupying an intermediate position between metals and non-metals.

As for the elements of the secondary subgroups, they are all metals.

Thus, the conditional boundary between metal elements and non-metal elements runs along the diagonal B (boron) - Si (silicon) - As (arsenic) - Te (tellurium) - At (astatine) (track it in the table of D. I. Mendeleev ).

Metal atoms have relatively large dimensions (radii), so their outer electrons are far from the nucleus and are weakly bound to it. The second feature that is inherent in the atoms of the most active metals is the presence of 1-3 electrons at the external energy level. From this follows the most characteristic chemical property of all metals - their reducing ability, that is, the ability of atoms to easily give up external electrons, turning into positive ions. Metals - free atoms and simple substances - cannot be oxidizing agents, that is, metal atoms cannot attach electrons to themselves.

However, it should be borne in mind that the division of chemical elements into metals and non-metals is conditional. Recall, for example, the properties of allotropic modifications of tin: gray tin, or α-tin, is a non-metal, and white tin, or β-tin, is a metal. Another example is carbon modifications: diamond is a non-metal, while graphite has some of the characteristic properties of a metal, such as electrical conductivity. Chromium, zinc and aluminum are typical metals, but form amphoteric oxides and hydroxides. Conversely, tellurium and iodine are typical non-metals, but the simple substances formed by them have some properties inherent in metals.

New words and concepts

1. Diagonal B-Si-As-Te-At.
2. Alkali and alkaline earth metals.
3. Restorative properties of metals.
4. The relativity of the division of chemical elements into metals and non-metals.

Tasks for independent work

The purpose of the lesson: formation of a system of knowledge about the position of metals in the Periodic system and their general properties.

Lesson objectives:

educational - consider the position of metals in the system of elements D.I. Mendeleev, to introduce students to the basic properties of metals, to find out what causes them, to introduce the concept of corrosion of metals

Educational - be able to find metals in the PSCE table, be able to compare metals and non-metals, explain the reasons for the chemical and physical properties of metals, develop students' theoretical thinking and their ability to predict the properties of metals based on their structure.

nurturing - to promote the development of students' cognitive interest in the study of chemistry

Lesson type: lesson learning new material.

Teaching methods : verbal and visual

During the classes:

Lesson timing.

Organizational moment (1 min.)

Knowledge update(3 min)

Learning new material

1.1. Position in the periodic system. (10 min)

1.2. Features of the electronic structure of atoms. (10 min)

1.3. Restorative properties of metals. (10 min)

2.1. Metal connection. (5 minutes)

4. Emotional release 2 min

2.2. Physical properties. (10 min)

3. Chemical properties. (17 min)

4. Corrosion of metals. (5 min)

Fixing (15 min)

Homework (3 min)

Summary of the lesson (1 min)

Organizing time

(Mutual greeting, fixation of those present).

Knowledge update. At the beginning of the lesson, the teacher focuses the students' attention on the significance of the new topic, determined by the role that metals play in nature and in all spheres of human activity.. Industry

The teacher reads the riddle:

I am hard, malleable and plastic,

Brilliant, everyone needs, practical.

I already gave you a hint

So who am I...? and offers to write down the answer in a notebook in the form of a lesson topic?

Learning new material

Lecture plan.

1. Characteristics of the metal element.

1.2. Features of the electronic structure of atoms.

1.3. Restorative properties of metals.

2. Characteristics of a simple substance.

2.1. Metal connection.

2.2. physical properties.

3. Chemical properties.

4. Corrosion of metals.

1.1. Position in the periodic system.

The conditional boundary between metal elements and non-metal elements runs along the diagonal B (boron) - (silicon) - Si (arsenic) - Te (tellurium) - As (astatine) (track it in the table of D. I. Mendeleev) ..

The initial elements formthe main subgroup of group I and are called alkali metals . They got their name from the name of their corresponding hydroxides, which are highly soluble in water - alkalis.

Of the elements of the main subgroups of the following groups, metals include: in group IV germanium, tin, lead (32.50.82) (the first two elements are carbon and silicon - non-metals), in group V antimony and bismuth (51.83) (the first three elements are non-metals), in group VI only the last element - polonium (84) - is a pronounced metal. In the main subgroups of groups VII and VIII, all elements are typical non-metals.

As for the elements of the secondary subgroups, they are all metals.

Alkali metal atoms contain only one electron at the external energy level, which they easily donate during chemical interactions, therefore they are the strongest reducing agents. It is clear that, in accordance with an increase in the radius of the atom, the reducing properties of alkali metals increase from lithium to francium.

Following the alkali metals, the elements that make upthe main subgroup of group II, are also typical metals with a strong reducing ability (their atoms contain two electrons at the outer level).Of these metals, calcium, strontium, barium and radium are called alkaline earth metals. . These metals got this name because their oxides, which the alchemists called "earths", form alkalis when dissolved in water.

Metals also include elementsthe main subgroup of group III, excluding boron.

Group 3 includes metals called the aluminum subgroup.

1.2 Features of the electronic structure of metals.

Based on the knowledge gained, students themselves formulate the definition of "metal"

Metals are chemical elements whose atoms donate electrons from the outer (and sometimes pre-outer) electron layer, turning into positive ions. Metals are reducing agents. This is due to the small number of electrons in the outer layer, the large radius of the atoms, as a result of which these electrons are weakly retained with the nucleus.Metal atoms have relatively large sizes (radii), therefore their outer electrons are also significantly removed from the nucleus and are weakly bound to it. And the second feature that is inherent in the atoms of the most active metals isthe presence of 1-3 electrons in the external energy level.
Metal atoms have similarities in the structure of the outer electron layer, which is formed by a small number of electrons (mostly no more than three).
This statement can be illustrated by the examples of Na, aluminum Al and zinc Zn. Drawing up diagrams of the structure of atoms, if desired, you can draw up electronic formulas and give examples of the structure of elements of large periods, such as zinc.

Due to the fact that the electrons of the outer layer of metal atoms are weakly bound to the nucleus, they can be “given away” to other particles, which happens during chemical reactions:

The property of metal atoms to donate electrons is their characteristic chemical property and indicates that metals exhibit reducing properties.

1.3 Reducing properties of metals.

How the oxidizing power of elements changesIIIperiod?

(Oxidative properties increase in periods, and reduction properties weaken. The reason for the change in these properties is an increase in the number of electrons in the last orbital.)

How do the oxidizing properties of the elements of the 4th group of the main subgroup change?(from bottom to top, oxidizing properties are enhanced. The reason for the change in these properties is a decrease in the radius of the atom (it is easier to accept than to give away)

Based on the position of metals in the Periodic system, what conclusion can be drawn about the redox properties of metal elements?

(Metals are reducing agents in chemical reactions, because they donate their valence electrons)

Students answer that the strength of the bond between valence electrons and the nucleus depends on two factors:the charge of the nucleus and the radius of the atom. .

(recording the conclusion in students' notebooks) in periods with an increase in the charge of the nucleus, the restorative properties decrease.

For elements - metals of secondary subgroups, the properties are slightly different.

The teacher offers to compare the activity of the elements of the secondary subgroup.Cu, Ag, Au – activityb elements - metals drops. This pattern is also observed in the elements of the second secondary subgroupZn, CD, hg.The increase in electrons at the outer level, so the reducing properties are weakened

For elements of secondary subgroups - these are elements of 4-7 periods 31-36, 49-54 - with an increase in the ordinal element, the radius of the atoms will change little, and the value of the charge of the nucleus increases significantly, therefore, the strength of the bond of valence electrons with the nucleus increases, reducing properties weaken.

2.1. Metal connection.

The metallic bond is carried out through the mutual attraction of atom-ions and relatively free electrons.

Picture 1.
The structure of the crystal lattice of metals

In metals, valence electrons are held by atoms extremely weakly and are able to migrate. Atoms left without external electrons acquire a positive charge. They form a metallic crystal lattice.

A set of socialized valence electrons (electron gas), negatively charged, holds positive metal ions at certain points in space - the nodes of the crystal lattice, for example, silver metal.

External electrons can move freely and randomly, therefore metals are characterized by high electrical conductivity (especially gold, silver, copper, aluminum).

Chemical bond involves a certain type of crystal lattice. The metallic chemical bond promotes the formation of crystals with a metallic crystal lattice. At the nodes of the crystal lattice are atom-ions of metals, and between them are freely moving electrons. The metallic bond differs from the ionic one, because no anions, although there are cations. It also differs from the covalent one, because no shared electron pairs are formed.

Emotional discharge

The absence of what metal was described by Academician A.E. Fersman?

There would be a horror of destruction on the streets: there would be no rails, no wagons, no steam locomotives, no cars, even pavement stones would turn into clay dust, and plants would begin to wither and die without this metal. Destruction by a hurricane would have passed over the entire Earth, and the death of mankind would have become inevitable. However, a person would not have lived up to this moment, because having lost three grams of this metal in his body and in his blood, he would have ceased to exist before the drawn events would have unfolded (Answer: All people would have died, having lost iron in their blood)

Name the counterfeiter's metal

The name of the metal was given by the Spanish conquistadors, who in the middle of the 16th century. first met in South America (on the territory of modern Colombia) with a new metal that looks like silver. The name of the metal literally means "little silver", "silver".

Such a dismissive name is explained by the exceptional refractoriness of the metal, which was not amenable to remelting, did not find application for a long time and was valued half as much as silver. They used this metal to make counterfeit coins.

Today, this metal, used as a catalyst and in jewelry, is one of the most expensive.

It does not exist in its pure form in nature. Native platinum is usually a natural alloy with other noble (palladium, iridium, rhodium, ruthenium, osmium) and base (iron, copper, nickel, lead, silicon) metals. To obtain it, nuggets are heated in boilers with "aqua regia" (a mixture of nitric and hydrochloric acid) and then "finished" by numerous chemical reactions, heating and melting.

Thus, the crystal lattice depends and is determined by the type of chemical bond, but at the same time is the cause for physical properties.

2.2. physical properties.

The teacher emphasizes that the physical properties of metals are determined precisely by their structure.

A)hardness All metals except mercury are solids under normal conditions. The mildest are sodium, potassium. They can be cut with a knife; hardest chrome - scratches glass

b)density. Metals are divided into soft (5g/cm³) and heavy (less than 5g/cm³).

V)fusibility. Metals are divided into fusible and refractory.

G)electrical conductivity, thermal conductivity metals is due to their structure. Chaotically moving electrons under the influence of an electric voltage acquire a directed movement, resulting in an electric current.

With an increase in temperature, the amplitude of the movement of atoms and ions located in the nodes of the crystal lattice increases sharply, and this interferes with the movement of electrons, and the electrical conductivity of metals decreases.

It should be noted that in some non-metals, with increasing temperature, the electrical conductivity increases, for example, in graphite, while with increasing temperature, some covalent bonds are destroyed, and the number of freely moving electrons increases.

e)metallic luster - Electrons filling the interatomic space reflect light rays, and do not transmit like glass. They fall on the nodes of the crystal lattice. Therefore, all metals in the crystalline state have a metallic luster. For most metals, all the rays of the visible part of the spectrum are equally scattered, so they have a silvery-white color. Only gold and copper absorb short wavelengths to a large extent and reflect long wavelengths of the light spectrum, so they have a yellow color. The most brilliant metals are mercury, silver, palladium. All metals in powder exceptAlAndmg, lose their luster and are black or dark gray in color.

e)plastic

The mechanical effect on a crystal with a metal lattice causes only a displacement of the layers of atoms and is not accompanied by bond breaking, and therefore the metal is characterized by high plasticity.

3. Chemical properties.

According to their chemical properties, all metals are reducing agents, they all give up valence electrons relatively easily, pass into positively charged ions, that is, they are oxidized . The reducing activity of a metal in chemical reactions occurring in aqueous solutions reflects its position in the electrochemical series of metal voltages (Discovered and compiled by Beketov)

The further to the left a metal is in the electrochemical series of metal voltages, the more powerful the reducing agent is, the strongest reducing agent is metallic lithium, gold is the weakest, and, conversely, the gold (III) ion is the strongest oxidizing agent, lithium (I) is the most weak.

Each metal is able to restore from salts in solution those metals that are in a series of voltages after it, for example, iron can displace copper from solutions of its salts. However, it should be remembered that alkali and alkaline earth metals will interact directly with water.

Metals, standing in the series of voltages to the left of hydrogen, are able to displace it from solutions of dilute acids, while dissolving in them.

The reducing activity of a metal does not always correspond to its position in the periodic system, because when determining the place of a metal in a series, not only its ability to donate electrons is taken into account, but also the energy expended on the destruction of the metal crystal lattice, as well as the energy expended on the hydration of ions.

Interaction with simple substances

WITHoxygen most metals form oxides - amphoteric and basic:

4Li+O 2 = 2Li 2 O

4Al + 3O 2 = 2Al 2 O 3 .

Alkali metals, with the exception of lithium, form peroxides:

2Na+O 2 = Na 2 O 2 .

WITHhalogens metals form salts of hydrohalic acids, for example,

Cu + Cl 2 = CuCl 2 .

WITHhydrogen the most active metals form ionic hydrides - salt-like substances in which hydrogen has an oxidation state of -1.

2Na+H 2 = 2NaH.

WITHgray metals form sulfides - salts of hydrosulfide acid:

Zn + S = ZnS.

WITHnitrogen some metals form nitrides, the reaction almost always proceeds when heated:

3Mg+N 2 =Mg 3 N 2 .

WITHcarbon carbides are formed.

4Al + 3C = Al 3 C 4 .

WITHphosphorus - phosphides:

3Ca + 2P = Ca 3 P 2 .

Metals can interact with each other to formintermetallic compounds :

2Na + Sb = Na 2 sb,

3Cu + Au = Cu 3 Au.

Metals can dissolve in each other at high temperature without interaction, forming alloys.

The ratio of metals to acids.

Most often in chemical practice such strong acids as sulfuric H 2 SO 4 , hydrochloric HCl and nitric HNO 3 .

WithHCl

The hydrogen ions H formed in this process + act as an oxidizing agentmetals in the activity series to the left of hydrogen . The interaction proceeds according to the scheme:

Me + HCl - salt + H 2

2 Al + 6 HCl → 2 AlCl 3 + 3 H 2

2│Al 0 – 3 e - → Al 3+ - oxidation

3│2H + + 2 e - → H 2 - recovery

"Aqua regia" (formerly called vodka acids) is a mixture of one volume of nitric acid and three to four volumes of concentrated hydrochloric acid, which has a very high oxidative activity. Such a mixture is capable of dissolving some low-active metals that do not interact with nitric acid. Among them is the "king of metals" - gold. This effect of "aqua regia" is explained by the fact that nitric acid oxidizes hydrochloric acid with the release of free chlorine and the formation of nitrogen (III) chlorine oxide, or nitrosyl chloride - NOCl:

Gold oxidation reactions proceed according to the following equations:

Au + HNO3 + 4 HCl → H + NO + 2H2O

If acids can interact with bases and basic oxides, and the key element in their composition is a metal, then is it possible for metals to interact with acids. Let's check it experimentally.

Magnesium interacts with acid under normal conditions, zinc - when heated, copper - does not interact.

A range of voltages are used in practice for a comparative assessment of the chemical activity of metals in reactions with aqueous solutions of salts and acids and for the assessment of cathodic and anodic processes during electrolysis:

Metals to the left are stronger reducing agents, than the metals to the right:they displace the latter from salt solutions . Metals in the row to the left of hydrogen displace hydrogen when interacting with aqueous solutions of non-oxidizing acids; the most active metals (up to and including aluminum) - and when interacting with water.

Metals in the row to the right of hydrogen do not interact with aqueous solutions of non-oxidizing acids under normal conditions.

During electrolysis, metals to the right of hydrogen are released at the cathode; the reduction of metals of moderate activity is accompanied by the release of hydrogen; the most active metals (up to aluminum) cannot be isolated from aqueous solutions of salts under normal conditions.

4. Corrosion of metals – physical-chemical or chemical interaction between a metal (alloy) and a medium, leading to a deterioration in the functional properties of the metal (alloy), the medium or the technical system that includes them.

The word corrosion comes from the Latin "corrodo" - "to gnaw" (Late Latin "corrosio" means "corrosion").

Corrosion is caused by the chemical reaction of a metal with environmental substances occurring at the interface between the metal and the medium. Most often, this is the oxidation of a metal, for example, with atmospheric oxygen or acids contained in solutions with which the metal comes into contact. Metals located in the voltage series (activity series) to the left of hydrogen, including iron, are especially susceptible to this.

As a result of corrosion, iron rusts. This process is very complex and includes several stages. It can be described by the overall equation:

4Fe + 6H 2 O (moisture) + 3O 2 (air) = 4Fe(OH) 3

Iron(III) hydroxide is very unstable, quickly loses water and turns into iron(III) oxide. This compound does not protect the iron surface from further oxidation. As a result, the iron object can be completely destroyed.

To slow down corrosion, varnishes and paints, mineral oils and grease are applied to the metal surface. Underground structures are covered with a thick layer of bitumen or polyethylene. The interior surfaces of steel pipes and tanks are protected with cheap cement coatings.

For steel products, so-called rust converters containing phosphoric acid (H 3 RO 4 ) and its salts. They dissolve the remains of oxides and form a dense and durable film of phosphates, which is able to protect the surface of the product for some time. Then the metal is coated with a primer layer, which should fit well on the surface and have protective properties (usually red lead or zinc chromate is used). Only then can varnish or paint be applied.

Fixing (15 min)

Teacher:

Now, to fix it, let's do a test.

Solve test tasks

1.Select a group of elements that contains only metals:

A) Al, As, P;B) Mg, Ca, Si;IN) K, Ca, Pb

2. Select a group in which there are only simple substances - non-metals:

A) K 2 Oh, SO 2 , SiO 2 ; B) H 2 , Cl 2 , I 2 ; IN)Ca, Ba, HCl;

3. Indicate what is common in the structure of K and Li atoms:

A) 2 electrons on the last electron layer;

B) 1 electron on the last electron layer;

C) the same number of electronic layers.

4. Metal calcium exhibits properties:

A) an oxidizing agent

B) reducing agent;

C) an oxidizing or reducing agent, depending on the conditions.

5. The metallic properties of sodium are weaker than those of -

A) magnesium; B) potassium; B) lithium.

6. Inactive metals include:

A) aluminum, copper, zinc; B) mercury, silver, copper;

C) calcium, beryllium, silver.

7. What physical property is not common to all metals:

A) electrical conductivity, B) thermal conductivity,

C) solid state of aggregation under normal conditions,

D) metallic luster

8. Metals, when interacting with non-metals, exhibit the following properties:

a) oxidizing;

b) recovery;

c) both oxidizing and reducing;

d) do not participate in redox reactions.

9. In the periodic system, typical metals are located

a) the top

b) bottom

in the upper right corner

d) lower left corner

Part B. The answer to the tasks of this part is a set of letters that should be written down

Set a match.

With an increase in the ordinal number of an element in the main subgroup of group II of the Periodic system, the properties of the elements and the substances they form change as follows:

1) the number of electrons in the outer level

A) increases

3) electronegativity

4) restorative properties

B) decreases

B) does not change

(Answers: 1 -D, 2 -A, 3 -C, 4-B, 5-D)

TASKS FOR REINFORCEMENT

№1. Finish the equations of practically feasible reactions, name the reaction products

Li + H 2 O=

Cu + H 2 O=Cu( Oh) 2 + H 2

Ba+H 2 O=

Mg + H 2 O=

Ca+HCl=

2 Na+2 H 2 SO 4 ( TO)= Na 2 SO 4 + SO 2 + 2H 2 O

HCl + Zn =

H 2 SO 4 ( To)+ Cu=CuSO 4 + SO 2 + H 2 O

H 2 S + Mg \u003d MgS + H 2

HCl + Cu =

Homework: notes in notebooks, reports on the use of metals.

Teacher Offers to create a syncwine on the topic.

Line 1: Noun (one per topic) (Metals)

2nd line: two adjectives

3rd line: three verbs

4 line: four words combined into a sentence

Line 5: a word expressing the essence of this topic.

Lesson summary

Teacher : And so, we examined the structure and physical properties of metals, their position in the periodic system of chemical elements D.I. Mendeleev.

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Slides captions:

The position of metals in the Periodic system D.I. Mendeleev. Features of the structure of atoms, properties.

The purpose of the lesson: 1. based on the position of metals in the PSCE, come to an understanding of the structural features of their atoms and crystals (metal chemical bond and crystal metal lattice). 2.Summarize and expand knowledge about the physical properties of metals and their classifications. 3. Develop the ability to analyze, draw conclusions based on the position of metals in the periodic table of chemical elements.

COPPER I go for a small coin, I like to ring in bells, They erect a monument to me for this And they know: my name is….

IRON To plow and build - he can do anything, if a coal helps him in that ...

Metals are a group of substances with common properties.

Metals are elements of groups I - III of the main subgroups, and groups IV-VIII of secondary subgroups I group II group III group IV group V group VI group VII group VIII group Na Mg Al Ti V Cr Mn Fe

Of the 109 PSCE elements, 85 are metals: highlighted in blue, green and pink (except for H and He)

The position of an element in PS reflects the structure of its atoms. POSITION OF AN ELEMENT IN THE PERIODIC SYSTEM STRUCTURE OF ITS ATOMS Serial number of an element in the periodic system Charge of the atomic nucleus Total number of electrons Group number The number of electrons in the external energy level. Highest valency of the element, oxidation state Period number The number of energy levels. The number of sublevels on the outer energy level

Sodium atom model

The electronic structure of the sodium atom

Task 2. Make a diagram of the electronic structure of the aluminum and calcium atom in a notebook on your own, following the example of the sodium atom.

Conclusion: 1. Metals are elements that have 1-3 electrons on the external energy level, less often 4-6. 2. Metals are chemical elements whose atoms donate electrons of the outer (and sometimes pre-outer) electron layer turning into positive ions. Metals are reducing agents. This is due to the small number of electrons in the outer layer, the large radius of the atoms, as a result of which these electrons are weakly retained with the nucleus.

The metallic chemical bond is characterized by: - ​​delocalization of the bond, because a relatively small number of electrons simultaneously bind many nuclei; - valence electrons move freely throughout the piece of metal, which is generally electrically neutral; - metallic bond does not have directionality and saturation.

Crystal lattices of metals

Video information about metal crystals

The properties of metals are determined by the structure of their atoms. Metal property Characteristic property hardness All metals except mercury are solids under normal conditions. The mildest are sodium, potassium. They can be cut with a knife; the hardest chrome - scratches glass. Density Metals are divided into light (density 5g/cm) and heavy (density greater than 5g/cm). fusibility Metals are divided into fusible and refractory electrical conductivity, thermal conductivity Randomly moving electrons under the influence of an electric voltage acquire a directed movement, resulting in an electric current. metallic luster Electrons filling the interatomic space reflect light rays, and do not transmit plasticity like glass. The mechanical effect on a crystal with a metal lattice causes only a displacement of the layers of atoms and is not accompanied by bond breaking, and therefore the metal is characterized by high plasticity.

Check the assimilation of knowledge in the lesson by testing 1) The electronic formula of calcium. A) 1S 2 2S 2 2P 6 3S 1 B) 1S 2 2S 2 2 P 6 3 S 2 C) 1S 2 2S 2 2 P 6 3 S 2 3S 6 4S 1 D) 1S 2 2S 2 2 P 6 3 S 2 3 P 6 4 S 2

Test tasks 2 and 3 2) The electronic formula 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 has an atom: a) Na b) Ca c) Cu d) Zn 3) Electrical conductivity, metallic luster, plasticity, density of metals are determined: a ) the mass of atoms b) the melting point of metals c) the structure of metal atoms d) the presence of unpaired electrons

Test tasks 4 and 5 4) When interacting with non-metals, metals exhibit properties a) oxidizing; b) recovery; c) both oxidizing and reducing; d) do not participate in redox reactions; 5) In the periodic table, typical metals are located in: a) the upper part; b) lower part; in the upper right corner; d) lower left corner;

Correct answers Task number Correct answer 1 D 2 B 3 C 4 B 5 D

Preview:

The purpose and objectives of the lesson:

1. Based on the position of metals in the PSCE, bring students to an understanding of the structural features of their atoms and crystals (metal chemical bond and crystalline metal lattice), to study the general physical properties of metals. Review and generalize knowledge about the chemical bond and the metallic crystal lattice.
2. Develop the ability to analyze, draw conclusions about the structure of atoms based on the position of metals in the PSCE.
3. Develop the ability to master chemical terminology, clearly formulate and express your thoughts.
4. Cultivate independence of thinking in the course of educational activities.
5. To form an interest in the future profession.

Lesson form:

combined lesson with presentation

Methods and techniques:

Story, conversation, demonstration of video types of crystal lattices of metals, test, drawing up diagrams of the electronic structure of atoms, demonstration of a collection of samples of metals and alloys.

Equipment:

1. Table "Periodic system of chemical elements D.I. Mendeleev";
2. Presentation of the lesson on electronic media.
3. Collection of samples of metals and alloys.
4. Projector.
5. Cards with the table "Characteristics of the structure of the atom by position in the PSCE"
   

DURING THE CLASSES

I. Organizational moment of the lesson.

II. Statement and announcement of the topic of the lesson, its goals and objectives.

slide 1-2

III. Learning new material.

Teacher: Man has used metals since ancient times. Briefly about the history of the use of metals.

Post by 1 student. slide 3

In the beginning was the copper age.

By the end of the Stone Age, man discovered the possibility of using metals to make tools. The first such metal was copper.

The period of distribution of copper tools is called Eneolithic or Chalcolithic , which in Greek means "copper". Copper was processed with stone tools by cold forging. Copper nuggets were turned into products under heavy hammer blows. At the beginning of the Copper Age, only soft tools, jewelry, and household utensils were made from copper. It was with the discovery of copper and other metals that the blacksmith profession began to emerge.

Later, casting appeared, and then a person began to add tin or antimony to copper, to make bronze, which is more durable, strong, and fusible.

Message 2 student. slide 3

Bronze - an alloy of copper and tin. The chronological boundaries of the Bronze Age date back to the beginning of the 3rd millennium BC. before the beginning of the 1st millennium BC

Message 3 student. slide 4

The third and last period of the primitive era is characterized by the spread of iron metallurgy and iron tools and marks the Iron Age. In its modern meaning, this term was introduced in the middle of the 9th century by the Danish archaeologist K. Yu. Thomson and soon spread in literature along with the terms "Stone Age" and "Bronze Age".

Unlike other metals, iron, except meteorite, is almost never found in its pure form. Scientists suggest that the first iron that fell into the hands of man was of meteorite origin, and it is not for nothing that iron is called the “heavenly stone”. The largest meteorite was found in Africa, it weighed about sixty tons. And in the ice of Greenland found an iron meteorite weighing thirty-three tons.

And now the Iron Age continues. Indeed, at present, iron alloys make up almost 90% of all metals and metal alloys.

Teacher.

Gold and silver are noble metals currently used for making jewelry, as well as parts in electronics, the aerospace industry, and shipbuilding. Where can these metals be used in shipping? The exceptional importance of metals for the development of society is due, of course, to their unique properties. Name these properties.

Show students a collection of metal samples.

Students name such properties of metals as electrical and thermal conductivity, characteristic metallic luster, ductility, hardness (except for mercury), etc.

The teacher asks students a key question: what are these properties due to?

Expected response:the properties of substances are due to the structure of the molecules and atoms of these substances.

Slide 5. So, metals are a group of substances with common properties.

Presentation demonstration.

Teacher: Metals are elements of groups 1-3 of the main subgroups, and elements of groups 4-8 of secondary subgroups.

Slide 6. Task 1 . Independently, using PSCE, in a notebook, add the representatives of the groups that are metals.

							VIII

Listening to student responses selectively.

Teacher: metals will be the elements placed in the lower left corner of the PSCE.

The teacher emphasizes that in the PSCE, all elements located below the B - At diagonal will be metals, even those that have 4 electrons (Ge, Sn, Pb), 5 electrons (Sb, Bi), 6 electrons (Po) on the outer layer, because they have a large radius.

Thus, out of 109 PSCE elements, 85 are metals. slide number 7

Teacher: the position of the element in the PSCE reflects the structure of the element's atom. Using the tables that you received at the beginning of the lesson, we will characterize the structure of the sodium atom by its position in the PSCE.
Slide show 8.

What is a sodium atom? Look at the approximate model of the sodium atom, which shows the nucleus and electrons moving in orbits.

Show slide 9.Model of the sodium atom.

Let me remind you how a diagram of the electronic structure of an atom of an element is drawn up.

Slide show 10.You should get the following scheme of the electronic structure of the sodium atom.

Slide 11. Task 2. Make a diagram of the electronic structure of the calcium and aluminum atom in a notebook on your own, following the example of the sodium atom.

The teacher checks the work in the notebook.

What conclusion can be drawn about the electronic structure of metal atoms?

The outer energy level has 1-3 electrons. We remember that entering into chemical compounds, atoms tend to restore the full 8-electron shell of the outer energy level. To do this, metal atoms easily donate 1-3 electrons from the external level, turning into positively charged ions. At the same time, they exhibit restorative properties.

Slide show 12. Metals - These are chemical elements whose atoms donate electrons to the outer (and sometimes pre-outer) electron layer, turning into positive ions. Metals are reducing agents. This is due to the small number of electrons in the outer layer, the large radius of the atoms, as a result of which these electrons are weakly retained with the nucleus.

Consider simple substances - metals.

Slide show 13.

First, let us generalize information about the type of chemical bond formed by metal atoms and the structure of the crystal lattice

1. a relatively small number of electrons simultaneously bind many nuclei, the bond is delocalized;
2. valence electrons move freely throughout the piece of metal, which is generally electrically neutral;
3. the metallic bond does not have directionality and saturation.

Demonstration

slide 14 " Types of crystal lattices of metals»

Slide 15 Video of the crystal lattice of metals.

Students conclude that, in accordance with this structure, metals are characterized by common physical properties.

The teacher emphasizes that the physical properties of metals are determined precisely by their structure.

slide 16 The properties of metals are determined by the structure of their atoms

a) hardness All metals except mercury are solids under normal conditions. The mildest are sodium, potassium. They can be cut with a knife; the hardest chrome - scratches glass (demonstration).

b) density - metals are divided into light (5g/cm) and heavy (more than 5g/cm) (demonstration).

c) fusibility - metals are divided into fusible and refractory (demonstration).

G) electrical conductivity, thermal conductivitymetals is due to their structure. Chaotically moving electrons under the influence of an electric voltage acquire a directed movement, resulting in an electric current.

With an increase in temperature, the amplitude of the movement of atoms and ions located in the nodes of the crystal lattice increases sharply, and this interferes with the movement of electrons, and the electrical conductivity of metals decreases.

It should be noted that in some non-metals, with increasing temperature, the electrical conductivity increases, for example, in graphite, while with increasing temperature, some covalent bonds are destroyed, and the number of freely moving electrons increases.

e) metallic luster- electrons filling the interatomic space reflect light rays, and do not transmit, like glass.

Therefore, all metals in the crystalline state have a metallic luster. For most metals, all rays of the visible part of the spectrum are equally scattered, so they have a silvery-white color. Only gold and copper absorb short wavelengths to a large extent and reflect long wavelengths of the light spectrum, so they have yellow light. The most brilliant metals are mercury, silver, palladium. In powder, all metals, except for AI and Mg, lose their luster and are black or dark gray in color.

f) plasticity . The mechanical effect on a crystal with a metal lattice causes only a displacement of the layers of atoms and is not accompanied by bond breaking, and therefore the metal is characterized by high plasticity.

IV. Consolidation of the studied material.

Teacher: we examined the structure and physical properties of metals, their position in the periodic system of chemical elements D.I. Mendeleev. Now, to consolidate, we propose to perform a test.

Slides 15-16-17.

1) Electronic formula of calcium.

1. a) 1S 2 2S 2 2P 6 3S 1
2. b) 1S 2 2S 2 2P 6 3S 2
3. c) 1S 2 2S 2 2P 6 3S 2 3S 6 4S 1
4. d) 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2

2) Electronic formula 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 has an atom:

1. a) Na
2. b) Sa
3. c) Cu
4. d) Zn

3) Electrical conductivity, metallic luster, plasticity, density of metals are determined by:

1. a) mass of metal
2. b) the melting point of metals
3. c) the structure of metal atoms
4. d) the presence of unpaired electrons

4) Metals, when interacting with non-metals, exhibit properties

1. a) oxidizing;
2. b) recovery;
3. c) both oxidizing and reducing;
4. d) do not participate in redox reactions;

5) In the periodic table, typical metals are located in:

1. a) the top
VI. Homework.

The structure of metal atoms, their physical properties




As a result of studying this chapter, the student should:

know

• position of metals in the periodic system;
• biological role and application of metals in medicine;

be able to

• to characterize the features of the structure of atoms of metallic elements;
• describe the nature of a metallic bond and how it differs from a conventional covalent or ionic bond;
• explain the features of the crystal structure of metals;
• draw up equations of reactions that characterize the chemical properties of metals;
• describe the most important methods for obtaining metals, reactions for the detection of metal cathins;

own

The skills of interpreting the most important properties of metals in accordance with their position in the periodic system.

The position in the periodic system of elements of D. I. Mendeleev and the general properties of metals

More than 80% of the known chemical elements are metals, and in accordance with the structure of the electron shells, they include s-elements of the 1st and 2nd groups, all elements d- and /-families, p-elements of the 13th group (except for boron), as well as tin and lead (14th group), bismuth (15th group) and polonium (17th group). Most metals have 1-2 electrons in their outer energy level. This explains their weak electronegativity compared to non-metals.

Metal elements belonging to the 5-family make up the 1st and 2nd groups, and those belonging to the J-family - 3-12th groups. At atoms d- elements inside the periods from left to right, the ^-sublevels of the pre-external level are filled.

Metals, in whose atoms the /-sublevels of the third level from the end are filled, form families of lanthanides and actinides, each of which contains 14 elements.

physical properties. Metals have a crystalline structure, and they are characterized by three types of crystal lattices: cubic face-centered, hexagonal and cubic body-centered (see Fig. 5.7 in paragraph 5.2).

Electrical conductivity, which is the most important physical characteristic of the metallic state, is carried out by these electrons. For this reason, metals are classified as conductors of the first kind, i.e. to substances in the interatomic space of which there are always free electrons, and thanks to the latter, a current is created in the conductor. Type II conductors are electrolytes.

If a certain potential difference is applied to the metal, then free electrons acquire a directed motion and move from the negative pole to the positive one, i.e. a directed flow of moving electrons is created - an electric current.

The electrical conductivity of metals strongly depends on temperature. As the temperature rises, the vibrational motions of ions at the lattice sites increase, and this, in turn, greatly hinders the directed motion of electrons. As the temperature decreases, the thermal vibrations of ions in the nodes strongly decrease and the electrical conductivity increases. At temperatures close to absolute zero, most metals exhibit superconductivity.

The thermal conductivity of metals is also related to the mobility of free electrons and the vibrational motion of the atoms themselves. These oscillations propagate in the form of a system of elastic thermal waves over the entire crystal lattice. Free electrons collide with vibrating atoms and exchange energy with them. Therefore, when a metal is heated, thermal energy is immediately transferred from one atom to another due to free electrons. In this case, the temperature equalization occurs relatively quickly over the entire mass of the metal.

All metals except mercury are solids. Mercury is the only metal that is liquid under ordinary conditions: the melting point is -39°C. Most metals are dark gray to silvery white in color. In industry, there is a division of metals into ferrous and non-ferrous. Ferrous metals include iron and all its alloys, and the rest of the metals are non-ferrous. Sometimes precious metals are distinguished - gold and platinum metals.

By density, metals are divided into light and heavy. The former include those whose density is less than 5 g/cm 3 ; to the second - in which the density is more than 5 g / cm 3.

According to the values ​​of melting points, metals are divided into fusible (melting point less than 1000 ° C) and refractory (melting point more than 1500 ° C). The main mechanical properties include: elasticity - the ability to restore its original shape after the removal of deforming forces; plasticity - the state of a metal in which it is able to maintain a change in shape caused by the action of deforming forces after their action is terminated.

Chemical properties. The properties of metals are due to the characteristic structure of their outer electron shells.

As already mentioned, within a period, with an increase in the charge of the nucleus, the radii of atoms with the same number of electron shells decrease. In each period, the alkali metal atoms have the largest radii. The smaller the atomic radius, the greater the ionization energy, and the larger the atomic radius, the lower this energy. Since alkali metal atoms have the largest atomic radii, they are generally characterized by relatively low values ​​of ionization energy and electron affinity.

Free metals exhibit exclusively reducing properties.

Metals form oxides M x O y, for example:

With halogens, metals form halides, which are salts of the corresponding hydrohalic acids:



Metals are able to attach hydrogen, forming hydrides. The reaction usually proceeds at a temperature of 350-400°C:



Reactions of metals in the activity series of metals up to hydrogen with acids are characteristic. If a metal interacts with an acid whose anion is not an oxidizing agent, then the proton of the acid performs the functions of the oxidizing agent:



Some metals that form amphoteric oxides and hydroxides also react with alkalis:

Metals interact with concentrated sulfuric and nitric acids (see the relevant chapters for details).

When interacting with aqueous salt solutions, a neutral atom of a more active metal, being oxidized, restores a metal ion from a salt molecule:

Reactions proceed in accordance with the position of metals in the electrochemical series of voltages (see Chap. 8).

Active metals interact with water:

Receipt. Most metals in nature occur in the form of compounds, and only a few of them (noble and semi-noble) - in the native state.

Natural materials and rocks that contain metal compounds are called ores. All methods for obtaining metals from ores are based on reduction reactions. The reduction of anhydrous metal compounds at high temperatures is called the pyrometallurgical process. As reducing agents, either metals (metallothermy) or carbon (carbothermy) are used.

A special case of metallothermy is aluminothermy:

Metalthermy is usually used to obtain refractory metals such as titanium, molybdenum, chromium, tungsten, etc.:

Carbothermy is based on the thermal reduction of a metal from its oxide with carbon (or CO):



The recovery of metals from their oxides can also be carried out using hydrogen:



Metals can be reduced from aqueous solutions of salts by electrolysis. The cathodic reduction of metals from solutions or molten salts is called the electrometallurgical process.

Some methods of obtaining will be considered in more detail when studying specific representatives of metals.

Alloys. A characteristic feature of metals is their ability to mix with each other in the molten state and form homogeneous mixtures. They remain homogeneous even after cooling. The systems formed during the solidification of a molten mixture of metals are called alloys. In a broader sense, alloys can be considered as macroscopically homogeneous systems consisting of two or more metals (more rarely, metals and non-metals). The structure of alloys can be different. The constituent parts of alloys can form a solid solution, or a macrohomogeneous mechanical mixture, or a chemical compound (intermetallic compounds). The formation of one or another type of alloy depends on the activity of the metals. Systems in the form of solid solutions are formed between metals of the same group or metals whose atomic radii are close.

The chemical bond in alloys is metallic, due to which they have electrical and thermal conductivity, metallic luster (this is the brilliance of metals, for example, gold, steel, etc. shine), etc.

When metals interact with each other, the resulting compounds differ in properties from the properties of the constituent components. The formula composition of intermetallic compounds does not always satisfy the classical ideas about the valence of elements.

Thus, mercury combines with many metals to form solid or liquid compositions - alloys, called amalgams. Alkali and alkaline earth metals form stable amalgams, which are solids of the composition NaHg 9 , KHg 2 , Callg, etc.

Alloys, as a rule, have a melting point lower than the melting point of their constituent metals. The hardness of alloys is much higher than the hardness of individual metals. The corrosion resistance of many alloys is higher than that of individual metals.