B O most of the known chemical elements forms simple substances metals.

Metals include all elements of secondary (B) subgroups, as well as elements of the main subgroups located below the beryllium - astatine diagonal (Fig. 1). In addition, the chemical elements metals form the lanthanide and actinide groups.

Rice. 1. The location of metals among elements of subgroups A (highlighted in blue)

Compared to non-metal atoms, metal atoms have b O larger sizes and fewer external electrons, usually 1-2. Consequently, the outer electrons of metal atoms are weakly bound to the nucleus; metals easily give them up, manifesting themselves in chemical reactions restorative properties.

Let us consider the patterns of changes in some properties of metals in groups and periods.

In periodsWith As the nuclear charge increases, the radius of the atoms decreases. The nuclei of atoms attract outer electrons more and more, so the electronegativity of the atoms increases and the metallic properties decrease. Rice. 2.

Rice. 2. Change in metallic properties in periods

In the main subgroups From top to bottom, the number of electronic layers in metal atoms increases, therefore, the radius of the atoms increases. Then the outer electrons will be less strongly attracted to the nucleus, so there is a decrease in the electronegativity of the atoms and an increase in metallic properties. Rice. 3.

Rice. 3. Change in metallic properties in subgroups

The listed patterns are also characteristic of elements of secondary subgroups, with rare exceptions.

Atoms of metal elements tend to lose electrons. In chemical reactions, metals act only as reducing agents; they donate electrons and increase their oxidation state.

The atoms that make up simple nonmetal substances, as well as the atoms that make up the metal atoms, can accept electrons from metal atoms. complex substances, which are able to lower their oxidation state. For example:

2Na 0 + S 0 = Na +1 2 S -2

Zn 0 + 2H +1 Cl = Zn +2 Cl 2 + H 0 2

Not all metals have the same chemical reactivity. Some metals practically do not enter into chemical reactions under normal conditions; they are called noble metals. Noble metals include: gold, silver, platinum, osmium, iridium, palladium, ruthenium, rhodium.

Noble metals are very rare in nature and are almost always found in the native state (Fig. 4). Despite their high resistance to corrosion-oxidation, these metals still form oxides and other chemical compounds For example, everyone knows silver chlorides and nitrates.

Rice. 4. Gold nugget

Summing up the lesson

In this lesson, you examined the position of the chemical elements of metals in the Periodic Table, as well as the structural features of the atoms of these elements, which determine the properties of simple and complex substances. You learned why there are much more chemical elements of metals than non-metals.

Bibliography

1. Orzhekovsky P.A. Chemistry: 9th grade: general education. establishment / P.A. Orzhekovsky, L.M. Meshcheryakova, M.M. Shalashova. - M.: Astrel, 2013. (§28)
2. Rudzitis G.E. Chemistry: inorganic. chemistry. Organ. chemistry: textbook. for 9th grade. / G.E. Rudzitis, F.G. Feldman. - M.: Education, OJSC “Moscow Textbooks”, 2009. (§34)
3. Khomchenko I.D. Collection of problems and exercises in chemistry for high school. - M.: RIA " New wave": Publisher Umerenkov, 2008. (p. 86-87)
4. Encyclopedia for children. Volume 17. Chemistry / Chapter. ed. V.A. Volodin, Ved. scientific ed. I. Leenson. - M.: Avanta+, 2003.

1. A unified collection of digital educational resources (video experiments on the topic) ().
2. Electronic version of the journal “Chemistry and Life” ().

Homework

1. With. 195-196 No. 7, A1-A4 from the textbook by P.A. Orzhekovsky “Chemistry: 9th grade” / P.A. Orzhekovsky, L.M. Meshcheryakova, M.M. Shalashova. - M.: Astrel, 2013.
2. What properties (oxidizing or reducing) can the Fe 3+ ion have? Illustrate your answer with reaction equations.
3. Compare the atomic radius, electronegativity, and reducing properties of sodium and magnesium.

Elements that form simple substances - metals, occupy the left bottom part periodic table (for clarity, we can say that they are located to the left of the diagonal connecting Be and polonium, No. 84), they also include elements of side (B) subgroups.

Metal atoms are characterized by a small number of electrons in the outer level. So, sodium has 1 electron at the outer level, magnesium has 2, and aluminum has 3 electrons. These electrons are relatively weakly bound to the nucleus, which causes the characteristic physical properties of metals:

• electrical conductivity,
• good thermal conductivity,
• malleability, ductility.
• Metals also have a characteristic metallic luster.

IN chemical in reactions, metals act as reducing agents:

1. When interacting with oxygen, metals form oxides, for example, magnesium burns to form magnesium oxide:
   2Mg + O2 = 2MgO

The most active metals (alkali) form peroxides when burning in air:

2Na + O 2 = Na 2 O 2 (sodium peroxide)

1. Reactive metals, such as sodium, react with water to form hydroxides:
   2Na + 2HOH = 2NaOH + H2

or oxides like magnesium when heated:

Mg + H 2 O = MgO + H 2

1. Metals located in the electrochemical voltage series to the left of hydrogen (H) displace hydrogen from acids (except nitric). Thus, zinc reacts with hydrochloric acid to form zinc chloride and hydrogen:
   Zn + 2HCl = ZnCl 2 + H 2

Metals, including those to the right of hydrogen, with the exception of gold and platinum, react with nitric acid to form various nitrogen compounds:

Cu + 4HNO 3 (conc.) = Cu(NO 3) 2 + 2H 2 O + 2NO 2

It is easier to arrange the coefficients in these equations using the electronic balance method. We indicate the oxidation states:

Cu 0 + 4HN +5 O 3 (conc.) = Cu +2 (NO 3) 2 + 2H 2 O + 2N +4 O 2

We write down elements with changed oxidation states:

** the coefficient for a substance containing this element is obtained by dividing the least common multiple by the number of electrons added or taken away (from this atom)

2. Experience. Receiving and collecting oxygen. Proof of the presence of oxygen in the vessel

In a school laboratory, oxygen is most often obtained by the decomposition of hydrogen peroxide in the presence of manganese (IV) oxide:

2H 2 O 2 = 2H 2 O + O 2

or by the decomposition of potassium permanganate when heated:

2KMnO 4 = K 2 MnO 4 + MnO 2 + O 2

To collect gas, the vessel is closed with a stopper with a gas outlet tube.

To prove the presence of oxygen in the vessel, a smoldering splinter is introduced into it - it flares up brightly.

To use presentation previews, create a Google account and log in to it: https://accounts.google.com

Slide captions:

Position of metals in the Periodic Table D.I. Mendeleev. Features of the structure of atoms, properties.

Objective 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 (metallic chemical bond and crystalline metal lattice). 2. Generalize and expand knowledge about the physical properties of metals and their classifications. 3. Develop the ability to analyze and draw conclusions based on the position of metals in the periodic table of chemical elements.

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

IRON He can plow and build - he can do everything if a coal helps him with it...

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 elements of PSCE, 85 are metals: highlighted in blue, green and pink(except H and He)

The position of an element in the PS reflects the structure of its atoms POSITION OF AN ELEMENT IN THE PERIODIC CHART STRUCTURE OF ITS ATOMS Ordinal number of the element in the periodic table Charge of the atomic nucleus Total number of electrons Group number Number of electrons in the external energy level. Highest valence of an element, oxidation state Number of period Number of energy levels. Number of sublevels at the external energy level

Sodium atom model

Electronic structure of the sodium atom

Task 2. Draw up a diagram of the electronic structure of the aluminum and calcium atom in your notebook yourself, following the example with the sodium atom.

Conclusion: 1. Metals are elements that have 1-3 electrons at the outer energy level, less often 4-6. 2. Metals are chemical elements whose atoms give up 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 and the large radius of the atoms, as a result of which these electrons are weakly retained with the nucleus.

A 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 entire piece of metal, which is generally electrically neutral; - the metal 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 Property characteristic hardness All metals except mercury, under normal conditions solids. The softest ones are sodium and potassium. They can be cut with a knife; The hardest chrome scratches glass. density Metals are divided into light (density 5 g/cm) and heavy (density more than 5 g/cm). fusibility Metals are divided into fusible and refractory electrical conductivity, thermal conductivity Chaotically moving electrons under the influence electrical voltage acquire directional movement, resulting in the generation of electric current. metallic luster Electrons filling the interatomic space reflect light rays, and do not transmit plasticity like glass. Mechanical impact on the crystal with metal grille causes only displacement of layers of atoms and is not accompanied by bond rupture, and therefore the metal is characterized by high ductility.

Check your knowledge in the lesson by testing 1) Electronic formula of calcium. A) 1S 2 2S 2 2Р 6 3S 1 B) 1S 2 2S 2 2 Р 6 3 S 2 C) 1S 2 2S 2 2 Р 6 3 S 2 3S 6 4S 1 D) 1S 2 2S 2 2 Р 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 by: a ) mass of atoms b) melting point of metals c) structure of metal atoms d) presence of unpaired electrons

Test tasks 4 and 5 4) Metals, when interacting with non-metals, exhibit a) oxidizing properties; b) restorative; c) both oxidative and reductive; 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 Variant of correct answer 1 D 2 B 3 C 4 B 5 D

Preview:

Purpose and objectives of the lesson:

1. Based on the position of metals in the PSHE, lead students to an understanding of the structural features of their atoms and crystals (metallic chemical bonds and crystalline metal lattice), and study the general physical properties of metals. Review and generalize knowledge about chemical bonding and the metal crystal lattice.
2. Develop the ability to analyze and draw conclusions about the structure of atoms based on the position of metals in the PSHE.
3. Develop the ability to master chemical terminology, clearly formulate and express your thoughts.
4. Foster independent thinking during educational activities.
5. Generate interest in your future profession.

Lesson format:

combined lesson using 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 table 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 PSHE”
   

DURING THE CLASSES

I. Organizing time lesson.

II. Setting and announcing 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.

Message from 1 student. Slide 3

In the beginning there was the Copper Age.

Towards 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 Chalcolithic or Chalcolithic , which means “copper” in Greek. Copper was processed using stone tools using the method cold forging. Copper nuggets were turned into products under heavy hammer blows. At the beginning of the Copper Age, only soft tools, jewelry, and objects were made from copper. household utensils. It was with the discovery of copper and other metals that the profession of a blacksmith began to emerge.

Later, casting appeared, and then man began to add tin or antimony to copper, making bronze, which was more durable, strong, and fusible.

Posted by student 2. 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. until the beginning of the 1st millennium BC.

Student Message 3. Slide 4

Third and last period The primitive era is characterized by the spread of iron metallurgy and iron tools and marks iron age. IN modern meaning this term was introduced into use in the middle of the 9th century by the Danish archaeologist K. Yu. Thomson and soon spread in the literature along with the terms “ stone Age" and "Bronze Age".

Unlike other metals, iron, except meteorite, is almost never found in 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 “stone of heaven.” The largest meteorite was found in Africa; it weighed about sixty tons. And an iron meteorite weighing thirty-three tons was found in the ice of Greenland.

And the Iron Age continues today. 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 manufacturing jewelry, as well as parts in electronics, aerospace, 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 mercury), etc.

The teacher asks students a key question: what determines these properties?

Expected response:the properties of substances are determined by 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 PSHE, add representatives of the groups that are metals in your notebook.

Listening to student responses selectively.

Teacher: metals will be the elements located in the lower left corner of the PSHE.

The teacher emphasizes that in PSHE 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), since they have a large radius.

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

Teacher: the position of an element in the PSCE reflects the atomic structure of the element. 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.
Show slide 8.

What is a sodium atom? Look at a close-up model of the sodium atom, showing the nucleus and electrons moving in orbits.

Demonstration of Slide 9.Model of the sodium atom.

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

Show slide 10.You should get the following diagram of the electronic structure of the sodium atom.

Slide 11. Task 2. Draw up a diagram of the electronic structure of the calcium and aluminum atom in your notebook yourself, 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?

There are 1-3 electrons in the outer energy level. We remember that when entering into chemical compounds, atoms strive to restore the full 8-electron shell of the outer energy level. To do this, metal atoms easily give up 1-3 electrons from the outer level, turning into positively charged ions. At the same time, they exhibit restorative properties.

Show slide 12. Metals – these are chemical elements whose atoms give up 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 and the large radius of the atoms, as a result of which these electrons are weakly retained with the nucleus.

Let's consider simple substances - metals.

Show slide 13.

First, let's summarize information about the type of chemical bond formed by metal atoms and the structure 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 metal bond lacks directionality and saturation.

Demonstration

Slide 14 " Types of metal crystal lattices»

Slide 15 Video of the crystal lattice of metals.

Students conclude that in accordance with this structure, metals are characterized by general 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 solid substances under normal conditions. The softest ones are sodium and potassium. They can be cut with a knife; the hardest chrome scratches glass (demonstration).

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

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

G) electrical conductivity, thermal conductivitymetals is determined by their structure. Chaotically moving electrons under the influence of electrical voltage acquire directional movement, resulting in an electric current.

As the temperature rises, the amplitude of movement of atoms and ions located at 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 for some non-metals, the electrical conductivity increases with increasing temperature, for example, for graphite, while with increasing temperature some of them are destroyed. covalent bonds, and the number of freely moving electrons increases.

d) metallic shine– electrons filling the interatomic space reflect light rays, and do not transmit them, like glass.

Therefore, all metals in crystalline state have a metallic luster. For most metals, all rays of the visible part of the spectrum are scattered equally, 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, and therefore have yellow light. The most shiny metals are mercury, silver, palladium. In powder, all metals, except AI and Mg, lose their luster and have a black or dark gray color.

e) plasticity . Mechanical action on a crystal with a metal lattice causes only displacement of layers of atoms and is not accompanied by bond rupture, 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 table of chemical elements D.I. Mendeleev. Now, to consolidate, we suggest performing 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) Ca
3. c) Cu
4. d) Zn

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

1. a) mass of metal
2. b) 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) oxidative;
2. b) restorative;
3. c) both oxidative and reductive;
4. d) do not participate in redox reactions;

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

1. a) the top part;
VI. Homework.

The structure of metal atoms, their physical properties




1. Position of metals in the table of elements

Metals are located mainly in the left and lower parts of the PSHE. These include:




2. Structure of metal atoms

Metal atoms usually have 1-3 electrons in their outer energy level. Their atoms have a large radius and easily give up valence electrons, i.e. exhibit restorative properties.



3. Physical properties of metals





Changes in the electrical conductivity of a metal when it is heated and cooled


Metal connection - this is the bond that free electrons carry out between cations in a metal crystal lattice.

4. Obtaining metals




1. Reduction of metals from oxides with coal or carbon monoxide

Me x O y + C = CO 2 + Me or Me x O y + CO = CO 2 + Me

2. Roasting of sulfides followed by reduction

Stage 1 – Me x S y +O 2 =Me x O y +SO 2

Stage 2 -Me x O y + C = CO 2 + Me or Me x O y + CO = CO 2 + Me

3 Aluminothermy (reduction with a more active metal)

Me x O y + Al = Al 2 O 3 + Me

4. Hydrothermy - for the production of high purity metals

Me x O y + H 2 = H 2 O + Me

5. Reduction of metals by electric current (electrolysis)

1) Alkali and alkaline earth metals obtained in industry by electrolysis molten salts (chlorides):

2NaCl – melt, elect. current. → 2 Na + Cl 2

CaCl 2 – melt, elect. current.→ Ca+Cl2

hydroxide melts:

4NaOH – melt, elect. current.→ 4 Na + O 2 + 2 H 2 O

2) Aluminum in industry it is obtained by electrolysis aluminum oxide melt I in Na 3 AlF 6 cryolite (from bauxite):

2Al 2 O 3 – melt in cryolite, electr. current.→ 4 Al + 3 O 2

3) Electrolysis of aqueous salt solutions use to obtain metals of intermediate activity and inactive:

2CuSO 4 +2H 2 O – solution, elect. current.→ 2 Cu + O 2 + 2 H 2 SO 4




5. Finding metals in nature

The most common in earth's crust metal - aluminum. Metals are found both in compounds and in free form.

1. Active – in the form of salts (sulfates, nitrates, chlorides, carbonates)

2. Moderate activity – in the form of oxides, sulfides ( Fe 3 O 4 , FeS 2 )

3. Noble – in free form ( Au, Pt, Ag)

CHEMICAL PROPERTIES OF METALS

Are common Chemical properties metals are presented in the table:







ASSIGNMENT TASKS

No. 1. Finish equations practicable reactions, name the reaction products

Li+ H 2 O =


Cu + H2O =


Al + H 2 O =


Ba + H2O =


Mg + H2O =

Ca+HCl=

Na + H 2 SO 4 (K) =


Al + H 2 S=

Ca + H3PO4 =


HCl + Zn =

H 2 SO 4 (k)+ Cu=


H 2 S + Mg =


HCl + Cu =


HNO 3 (K)+ С u =


H2S+Pt=

H3PO4 + Fe =


HNO 3 (p)+ Na=


Fe + Pb(NO 3) 2 =

No. 2. Complete the CRM, arrange the coefficients using the electronic balance method, indicate the oxidizing agent (reducing agent):

Al + O 2 =

Li + H 2 O =

Na + HNO 3 (k) =

Mg + Pb(NO 3) 2 =

Ni + HCl =

Ag + H 2 SO 4 (k) =

No. 3. Insert missing characters instead of dots (<, >or =)

Core charge	Li…Rb	Na…Al	Ca…K
Number of energy levels	Li…Rb	Na…Al	Ca…K
Number of outer electrons	Li…Rb	Na…Al	Ca…K
Atomic radius	Li…Rb	Na…Al	Ca…K
Restorative properties	Li…Rb	Na…Al	Ca…K

No. 4. Complete the CRM, arrange the coefficients using the electronic balance method, indicate the oxidizing agent (reducing agent):

K+ O 2 =

Mg+ H 2 O =

Pb+ HNO 3 (p) =

Fe+ CuCl 2 =

Zn + H 2 SO 4 (p) =

Zn + H 2 SO 4 (k) =


No. 5. Solve test problems

1.Select a group of elements that contains only metals: A) Al, As, P; B) Mg, Ca, Si; B ) K, Ca, Pb 2. Select a group that contains only simple substances - non-metals: A) K 2 O, SO 2, SiO 2; B) H 2, Cl 2, I 2; B )Ca, Ba, HCl; 3. Indicate the common features in the structure of the K and Li atoms: A) 2 electrons in the last electron layer; B) 1 electron in the last electron layer; IN) same number electronic layers. 4. Calcium metal exhibits the following properties: A) oxidizing agent; B) reducing agent; C) an oxidizing agent or a reducing agent, depending on the conditions. 5. Metallic properties sodium is weaker than - A) magnesium; B) potassium; C) lithium. 6. Inactive metals include: A) aluminum, copper, zinc; B) mercury, silver, copper; C) calcium, beryllium, silver. 7. What is the physical property is not common to all metals: A) electrical conductivity, B) thermal conductivity, B) hard state of aggregation under normal conditions, D) metallic shine

Part B. The answer to the tasks in this part is a set of letters that should be written down Match. With an increase in the ordinal number of the element in main subgroup Group II of the Periodic System, the properties of the elements and the substances they form change as follows:




In the periodic table, more than 3/4 of the places are occupied by: they are in groups I, II, III, in secondary subgroups of all groups. In addition, the heaviest elements of groups IV, V, VI and VII are metals. It should be noted, however, that many have amphoteric properties and can sometimes behave like non-metals.
A feature of the structure of metal atoms is the small number of electrons in the outer electronic layer, not exceeding three.
Metal atoms, as a rule, have large atomic radii. In periods, alkali metals have the largest atomic radii. Hence their highest chemical activity, i.e. metal atoms easily give up electrons, and are good reducing agents. The best reducing agents are groups I and II of the main subgroups.
In compounds, metals always exhibit a positive oxidation state, usually from +1 to +4.

Figure 70. Education scheme metal connection in a piece of metal

In compounds with non-metals, typical metals form a chemical bond of an ionic nature. In simple form, metal atoms are connected to each other by a so-called metallic bond.

Write this term down in your notebook.

Metallic bond is a special type of bond unique to metals. Its essence is that electrons are constantly detached from metal atoms, which move throughout the entire mass of a piece of metal (Fig. 70). Metal atoms, deprived of electrons, turn into positive ions, which tend to again attract freely moving electrons. At the same time, other metal atoms give up electrons. Thus, the so-called electron gas constantly circulates inside a piece of metal, which firmly binds all the metal atoms together. The electrons turn out to be, as it were, shared simultaneously by all the atoms of the metal. This special type of chemical bond between metal atoms determines both the physical and chemical properties of metals.

■ 1. How to explain the low electronegativity of metals?
2. How does a metallic bond occur?
3. What is the difference between a metallic bond and a covalent bond?



Rice. 71. Comparison of melting points of different metals

Metals have a number of similar physical properties that distinguish them from non-metals. The more valence electrons a metal has, the stronger the metal bond, the stronger the crystal lattice, the stronger and harder the metal, the higher its melting and boiling point, etc. The features of the physical properties of metals are discussed below.
All of them have a more or less pronounced luster, which is commonly called metallic. A metallic sheen is characteristic of a piece of metal as a whole. The powder contains dark-colored metals, with the exception of magnesium and aluminum, which retain a silvery-white color, and therefore aluminum dust is used to make “silver” paint. Many nonmetals have a greasy or glassy luster.
The color of the metals is quite uniform: it is either silver-white (,) or silver-gray (,). Only yellow color, a - red. Non-metals have a very diverse color: - lemon yellow, - red-brown, - red or white, - black.

Thus, according to color, metals are conventionally divided into ferrous and non-ferrous. Ferrous metals also include it. All other metals are called non-ferrous.

Under normal conditions, metals are solids with a crystalline structure. Among non-metals there are both solid (,), and liquid () and gaseous (,).
All metals, with the exception of mercury, are solid substances, so their melting point is above zero, only the melting point of mercury is -39°. The most refractory metal is , whose melting point is 3370°. The melting point of other metals lies within these limits (Fig. 71).
The melting points of non-metals are much lower than those of metals, for example oxygen -219°, hydrogen -259.4°, fluorine -218°, chlorine -101°, bromine -5.7°.



Rice. 72. Comparison of the hardness of metals with the hardness of diamond.

Metals have different hardness, which is compared to the hardness of diamond. The metal hardness index is determined special device- hardness tester. In this case, a steel ball or, in the case of greater hardness of the metal, a diamond cone is pressed into the mass of metal. The hardness of the metal is determined by the force of pressure and the depth of the formed hole.
Most hard metal is . Soft metals - , - are easily cut with a knife. The hardness of individual metals on the generally accepted ten-point hardness scale is shown in Fig. 72.

Metals, to a greater or lesser extent, have plasticity (malleability). Non-metals do not have this property. The most malleable metal is. It can be forged into gold foil 0.0001 mm thick - 500 times thinner than a human hair. At the same time, it is very fragile; You can even grind it into powder in a mortar.
Plasticity is the ability to undergo strong deformation without compromising mechanical strength. The plasticity of metals is used during their rolling, when huge hot metal bars are passed between crimping shafts, preparing sheets from them, during drawing, when wire is pulled out of them, during pressing, stamping, when under the influence of



Rice. 73. Comparison of metals by density.

pressure is applied to the heated metal a certain form, which it retains when cooled. Plasticity depends on the structure of the crystal lattice of metals.
All metals are insoluble in water, but soluble in each other in melts. A solid solution of one metal in another is called an alloy.

Based on their density, metals are divided into heavy and light. Those whose density is more than 3 g/cm3 are considered heavy (Fig. 73). The heaviest metal is . The lightest metals - , .- have a density even less than one. Great Application light metals were obtained in industry - and.
Metals are characterized by high electrical and thermal conductivity (Fig. 74), while non-metals have these properties to a weak extent. It has the greatest electrical and thermal conductivity, and is in second place. These properties of aluminum are quite high.



Rice. 74. Comparison of electrical conductivity and thermal conductivity of different metals

It should be noted that metals with high electrical conductivity also have high thermal conductivity.
Metals exhibit magnetic properties. If, upon contact with a magnet, a metal is attracted to it and then becomes a magnet itself, we say that the metal is magnetized. They are well magnetized, too. Such metals are called ferromagnetic. Nonmetals do not have magnetic properties.

■ 4. Make and fill out the following table:

Chemical properties of metals. Corrosion

The chemical and physical properties of metals are determined by the atomic structure and characteristics of the metal bond. All metals are distinguished by their ability to easily give up valence electrons. In this regard, they exhibit pronounced restorative properties. The degree of reduction activity of metals reflects the electrochemical series of voltages (see Appendix III, paragraph 6).
Knowing the position of the metal in this series, we can draw a conclusion about the comparative amount of energy spent on removing valence electrons from the atom. The closer to the beginning of the row, the easier the metal oxidizes. The most active metals are displaced from water under normal conditions to form an alkali:
2Na + 2H2O = 2NaOH + H2
Less active metals are displaced from water in the form of superheated steam and form
2Fe + 4H2O = Fe3O4 + 4H2
react with dilute and oxygen-free acids, displacing hydrogen from them:
Zn + 2HCl = ZnCl2 + H2
Metals coming after hydrogen cannot displace it from water and acids, but enter into redox reactions with acids without displacing hydrogen:
Cu + 2H2SO4 = CuSO4 + SO2 + H2O
All preceding metals displace subsequent metals from their salts:
Fe + CuSO4 = FeSO4 + Cu

Fe0 + Cu2+ = Fe2+ + Cu0
In all cases, the reacting metals are oxidized. Oxidation of metals is also observed in the direct interaction of metals with non-metals:
2Na + S = Na2S
2Fe + 3Сl2 = 2FeCl3
Most metals react actively with oxygen, forming different compositions (see page 38).

■ 5. How can the reduction activity of a metal be characterized using a range of stresses?

6. Give examples of metals that react with water like sodium and iron. Support your answer with reaction equations.

7. Compare the interaction of active metals and active nonmetals with water.
8. List the chemical properties of metals, supporting your answer with reaction equations.
9. Which of the following substances will iron react with: a) , b) slaked lime, c) copper carbonate, d) , e) zinc sulfate, f) ?
10. What gas and in what volume can be obtained by treating 5 kg of a mixture of copper and copper oxide with concentrated nitric acid, if the copper oxide in the mixture is 20%?

Oxidation of metals often leads to their destruction. Destruction of metals under the influence environment called corrosion.

Write down the definition of corrosion in your notebook.

Occurs under the influence of oxygen, moisture and carbon dioxide, as well as nitrogen oxides, etc. Corrosion caused by the direct interaction of a metal with the substance of its environment is called chemical or gas corrosion. For example, in chemical production, metal sometimes comes into contact with oxygen, chlorine, nitrogen oxides, etc., resulting in the formation of metal salts:
2Сu + О2 = 2СuО
In addition to gas or chemical corrosion, there is also electrochemical corrosion, which is much more common. In order to understand the scheme of electrochemical corrosion, consider a galvanic couple -.

Let's take zinc and copper plates (Fig. 75) and lower them into a solution of sulfuric acid, which, as we know, is contained in the solution in the form of ions:
H2SO4 = 2H+ + SO 2 4 —
By connecting zinc and copper plates through a galvanometer, we will detect the presence of electric current. This is explained by the fact that zinc atoms, giving up electrons, pass into solution in the form of ions:
Zn 0 - 2 e— → Zn +2
Electrons pass through the conductor to copper, and from copper to hydrogen ions:
N + + e— → Н 0

Hydrogen in the form of neutral atoms is released on the copper plate and gradually dissolves. Thus, copper, as if drawing electrons from zinc, causes the latter to dissolve faster, i.e., promotes oxidation. At the same time, a completely pure substance can remain in acid for some time without being affected by it at all.



Rice. 75. Scheme of formation of a galvanic couple during electrochemical corrosion. 1 - zinc; 2 - copper; 3 - hydrogen bubbles on the copper electrode; 4 - galvanometer

According to the same scheme, corrosion of a metal such as iron occurs, only the electrolyte in air is, and impurities in the iron play the role of the second electrode of the galvanic pair. These vapors are microscopic, so the destruction of the metal is much slower. The more active metal is usually subject to destruction. Thus, electrochemical corrosion is the oxidation of a metal, accompanied by the formation of galvanic couples. causes great damage to the national economy.

12. Define corrosion.
11. Can something that quickly oxidizes in air be considered corrosion, the interaction of zinc with hydrochloric acid, the interaction of aluminum with iron oxide during thermite welding, the production of hydrogen by the interaction of iron with superheated water vapor.

13. What is the difference between chemical and electrochemical corrosion?
There are many ways to combat corrosion. Metals (particularly iron) cover oil paint, forming a dense film on the metal surface that does not allow water vapor to pass through. Can coat metals, e.g. copper wire, a varnish that simultaneously protects the metal from corrosion and serves as an insulator.

Burnishing is a process in which iron is exposed to strong oxidizing agents, as a result of which the metal is covered with a film of oxides impermeable to gases, protecting it from exposure external environment. Most often this is magnetic oxide Fe304, which penetrates deeply into the metal layer and protects it from oxidation better than any paint. Ural roofing iron, blued, lasted on the roof without rusting for more than 100 years. The better the metal is polished, the denser and stronger the oxide film formed on its surface.

Enameling is very good view protection against corrosion of various utensils. Enamel is resistant not only to oxygen and water, but even to strong acids and alkalis. Unfortunately, enamel is very fragile and cracks quite easily upon impact and rapid temperature changes.
Very in interesting ways protection of metals from corrosion are, as well as nickel plating and tinning.
- This is a coating of metal with a layer of zinc (this is how iron is mainly protected). With such a coating, in the event of a violation of the surface film of zinc, zinc, as a more active metal, is first exposed to corrosion, but zinc resists corrosion well, since its surface is covered with a protective film of oxide, impermeable to water and oxygen.
With nickel plating (nickel plating) and tinning (tin plating), rusting of the iron does not occur until the layer of metal covering it is damaged. As soon as it is broken, corrosion of iron begins as the most active metal. But is a metal that is relatively susceptible to corrosion, so its film remains on the surface for a very long time. Copper objects are most often tinned, and then the galvanic couple of copper always leads to corrosion of tin, not copper, which is less active as a metal. By tinning iron, “tinplate” is obtained for the canning industry.

To protect against corrosion, you can influence not only the metal, but also the environment that surrounds it. If a certain amount of sodium chromate is added to hydrochloric acid, the reaction of hydrochloric acid with iron it will slow down so much that practically the acid can be transported in iron tanks, whereas this is usually impossible. Substances that slow down corrosion, and sometimes almost completely stop it, are called inhibitors - retarders (from Latin word inhibere - to slow down).

The nature of the action of inhibitors is different. They either create on the surface of metals protective film, or reduce the aggressiveness of the environment. The first type includes, for example, NaNO2, which slows down the corrosion of steel in water and salt solutions, which slows down the corrosion of aluminum in sulfuric acid, the second - organic compound CO(NH2)2 - urea, which very slows down dissolution in nitric acid copper and other metals. Animal proteins, some dried plants - celandine, buttercup, etc. have inhibitory properties.
Sometimes, in order to increase the resistance of a metal to corrosion, as well as to give it some more valuable properties, alloys with other metals are made from it.

■ 14. Write down in your notebook the listed methods of protecting metal from corrosion.
15. What determines the choice of method of protecting metal from corrosion?
16. What is an inhibitor? How is an inhibitor different from a catalyst?

Methods for smelting metals from ores

Metals can occur in nature in a native state. This is basically eg. It is extracted by mechanical washing from surrounding rocks. However, the vast majority of metals occur in nature in the form of compounds. At the same time, not everyone natural mineral suitable for obtaining the metal it contains. Consequently, not every mineral can be called a metal ore.
Rocks or minerals containing a particular metal in an amount that makes its industrial production economically profitable are called ores of that metal.

Write down the definition of ores.

Metals are obtained from ores in various ways.
1. If the ore is an oxide, then it is reduced with some reducing agent - most often carbon or carbon monoxide CO, less often - hydrogen, for example:
FesO4 + 4СО = 3Fe + 4CO2
2. If the ore is a sulfur compound, then it is first roasted:
2PbS + 3O2 = 2PbO + 2SO2
then the resulting oxide is reduced with coal:
РbО + С = РbО + CO
Metals are separated from chlorides by electrolysis from melts. For example, when sodium chloride NaCl melts, thermal dissociation of the substance occurs.
NaCl ⇄ Na + + Cl —
When a direct electric current is passed through this melt, the following processes occur:
a) at the cathode:
Na++ e— → Na 0
b) at the anode
Сl — - e— → Cl 0
Metals can also be obtained from other salts using this method.
4. Sometimes metals can be reduced from oxides by displacement at high temperature another, more active metal. This method has become especially widespread in the reduction of metals with aluminum and therefore was first called aluminothermy:
2Al + Fe2O3 = Al2O3 + 2Fe.
Aluminothermy will be discussed in more detail below.
In many cases, the ore may be mixed with big amount waste rock, for the removal of which, i.e. for the “enrichment” of ore, there are various methods, in particular the froth flotation method. For this purpose, mineral oils that have the property of selective adsorption are used. This means that they absorb ore particles, but not waste rock. The ore, crushed together with waste rock, is placed in huge vats of water and mineral oil. After this, the water is strongly foamed with air. The oil surrounds the air bubbles, forming a film on them. The result is a stable foam. Particles and ores are adsorbed and, together with air bubbles, rise to the top. The foam along with the ore is drained, and the waste rock remains at the bottom of the vat. Subsequently, the ore is easily freed from oil, which is again used for flotation.

■ 17. What is foam?
18. What properties must a metal have in order to be in a native state in nature?
19. Can any mineral or rock containing this or that metal?
20. List what types of metal ores you know.
21. Zinc occurs naturally as the mineral zinc blende, which contains zinc sulfide. Suggest a method for obtaining zinc from zinc blende.
22. From 2 tons of magnetic iron ore containing 80% magnetic iron oxide Fe3O4, 1.008 tons of iron are obtained. Calculate the practical yield of iron.
23. What metals can be obtained by electrolysis of salt solutions?
24. An alloy containing 4% carbon was prepared from iron obtained by reducing 5 tons of magnetic iron ore containing 13% impurities. How much alloy were you able to obtain?
25. What amount of zinc and sulfuric acid can be obtained from 242.5 tons of zinc blende ZnS containing 20% ​​waste rock?

31

Rationale for the periodic system of elements Since electrons in an atom are located at different energy levels and form quantum layers, it is logical to assume that...

2. Second group of the periodic table