Establish a correspondence between the symbol of a chemical element (in the given order) and the number of electrons in the external energy level of its atom. From the letters

Corresponding to the correct answers, you will make up the name of the installation, which will allow humanity to know the structure of the atom even more deeply (9 letters).

Number e per element symbol

Energy

Mg Si I F C Ba Sn Ca Br

2 cap o l s e m

4 a o v k a t d h i

7 v y l l n g o l r

1 Periodic repetition of the number of electrons at the outer level of an atom explains _______________ 2. The number of energy levels of an atom can be

determine by:
A. group number;
B. period number;
B. serial number.

4. Which of the characteristics chemical elements does not change in the main subgroups:
And the radius of the atom;
B number of electrons in the outer level;
B. the number of energy levels.

5. Common structure of atoms of elements with serial numbers 7 and 15:

A. the number of electrons in the outer level, B. the charge of the nucleus;

B. number of energy levels.

1 (2 points). The distribution of electrons by energy levels in the potassium atom:

A. 2e, 8e, 8e, 1e B. . 2nd, 8th,

18th, 8th, 1st
B. 2e, 1e D. 2e, 8e, 1e

2 (2 points). The number of electrons on the outer electron layer of an aluminum atom:

A. 1 B. 2 C. 3 D.4

3 (2 points). A simple substance with the most pronounced metallic properties:

A. Calcium B. Barium C. Strontium G. Radium

4 (2 points). View chemical bond V simple matter- aluminum:

A. Ionic B. Covalent polar

C. Metallic D. Covalent non-polar

5 (2 points). The number of energy levels for the elements of one subgroup from top to bottom:

A. Changes periodically. B. Does not change.

B. Increases. G. Decreases.

6 (2 points). The lithium atom differs from the lithium ion:

A. 3 next to the nucleus. B. The number of electrons in the outer energy level.

B. The number of protons. D. The number of neutrons.

7 (2 points). Reacts least vigorously with water:

A. Barium. B. Magnesium.

B. Calcium. G. Strontium

8 (2 points). Does not interact with sulfuric acid solution:

A. Aluminum. B. sodium

B. Magnesium. G. Copper

9 (2 points). Potassium hydroxide does not interact with a substance whose formula is:

A. Na2O B. AlCl3

B. Р2O5 D. Zn(NO3)2

10 (2 points). A series in which all substances react with iron:

A. Hcl, CO2, CO

B. CO2, HCl, S

B. H2, O2, CaO

G. O2, CuSO4, H2SO4

11 (9 points). Suggest three methods for producing sodium hydroxide. Support your answer with reaction equations.

12 (6 points). Carry out a chain of chemical transformations, composing the reaction equations in molecular and ionic forms, name the reaction products:

FeCl2 → Fe(OH)2 → FeSO4 → Fe(OH)2

13 (6 points). How, using any reagents (substances) and zinc, to get its oxide, base, salt? Write the reaction equations in molecular form.

14 (4 points). Write an equation for the chemical reaction between lithium and nitrogen. Identify the reducing agent and oxidizing agent in this reaction

What happens to the atoms of elements during chemical reactions? What are the properties of the elements? One answer can be given to both of these questions: the reason lies in the structure of the external In our article, we will consider the electronic of metals and nonmetals and find out the relationship between the structure of the external level and the properties of the elements.

Special properties of electrons

When a chemical reaction occurs between the molecules of two or more reagents, changes occur in the structure of the electron shells of atoms, while their nuclei remain unchanged. First, let's get acquainted with the characteristics of electrons located at the most distant levels of the atom from the nucleus. Negatively charged particles are arranged in layers at a certain distance from the nucleus and from each other. The space around the nucleus where electrons are most likely to be found is called the electron orbital. It contains about 90% of the negatively charged electron cloud. The electron itself in the atom exhibits the property of duality, it can simultaneously behave both as a particle and as a wave.

Rules for filling the electron shell of an atom

The number of energy levels on which the particles are located is equal to the number of the period where the element is located. What does the electronic composition indicate? It turned out that on the external energy level for s- and p-elements of the main subgroups of small and large periods corresponds to the number of the group. For example, lithium atoms of the first group, which have two layers, have one electron in the outer shell. Sulfur atoms contain six electrons at the last energy level, since the element is located in main subgroup the sixth group, etc. If we are talking about d-elements, then for them there is the following rule: the number of external negative particles is 1 (for chromium and copper) or 2. This is explained by the fact that as the charge of the nucleus of atoms increases, the internal d-sublevel is first filled and the external energy levels remain without changes.

Why do the properties of elements of small periods change?

Periods 1, 2, 3 and 7 are considered small. The smooth change in the properties of elements as nuclear charges increase, starting from active metals and ending with inert gases, is explained by a gradual increase in the number of electrons at the external level. The first elements in such periods are those whose atoms have only one or two electrons that can easily break away from the nucleus. In this case, a positively charged metal ion is formed.

Amphoteric elements, such as aluminum or zinc, fill their external energy levels with a small amount of electrons (1 for zinc, 3 for aluminum). Depending on the conditions of the chemical reaction, they can exhibit both the properties of metals and non-metals. Non-metallic elements of small periods contain from 4 to 7 negative particles on the outer shells of their atoms and complete it to an octet, attracting electrons from other atoms. For example, a non-metal with the highest electronegativity index - fluorine, has 7 electrons on the last layer and always takes one electron not only from metals, but also from active non-metallic elements: oxygen, chlorine, nitrogen. Small periods end, as well as large ones, with inert gases, whose monatomic molecules have completely completed external energy levels up to 8 electrons.

Features of the structure of atoms of large periods

The even rows of 4, 5, and 6 periods consist of elements whose outer shells contain only one or two electrons. As we said earlier, they fill the d- or f- sublevels of the penultimate layer with electrons. Usually these are typical metals. Physical and Chemical properties they change very slowly. Odd rows contain such elements, in which the external energy levels are filled with electrons according to the following scheme: metals - amphoteric element - non-metals - inert gas. We have already observed its manifestation in all small periods. For example, in an odd series of 4 periods, copper is a metal, zinc is an amphoterene, then from gallium to bromine, non-metallic properties are enhanced. The period ends with krypton, the atoms of which have a completely completed electron shell.

How to explain the division of elements into groups?

Each group - and there are eight of them in the short form of the table, is also divided into subgroups, called main and secondary. This classification reflects the different positions of electrons on the external energy level of the atoms of elements. It turned out that the elements of the main subgroups, for example, lithium, sodium, potassium, rubidium and cesium, the last electron is located on the s-sublevel. Elements of the 7th group of the main subgroup (halogens) fill their p-sublevel with negative particles.

For representatives side subgroups, such as chromium, filling the d-sublevel with electrons will be typical. And for the elements included in the family, the accumulation of negative charges occurs at the f-sublevel of the penultimate energy level. Moreover, the group number, as a rule, coincides with the number of electrons capable of forming chemical bonds.

In our article, we found out what structure the external energy levels of atoms of chemical elements have and determined their role in interatomic interactions.

E.N.FRENKEL

Chemistry tutorial

A guide for those who do not know, but want to learn and understand chemistry

Part I. Elements general chemistry
(first level of difficulty)

Continuation. See the beginning in No. 13, 18, 23/2007

Chapter 3. Elementary information about the structure of the atom.
Periodic law of D.I. Mendeleev

Remember what an atom is, what an atom consists of, whether an atom changes in chemical reactions.

An atom is an electrically neutral particle consisting of a positively charged nucleus and negatively charged electrons.

The number of electrons during chemical processes can change, but nuclear charge always stays the same. Knowing the distribution of electrons in an atom (the structure of an atom), one can predict many properties of a given atom, as well as the properties of simple and complex substances, of which it is included.

The structure of the atom, i.e. the composition of the nucleus and the distribution of electrons around the nucleus, it is easy to determine by the position of the element in periodic system.

In the periodic system of D.I. Mendeleev, chemical elements are arranged in a certain sequence. This sequence is closely related to the structure of the atoms of these elements. Each chemical element in the system is assigned serial number, in addition, for it you can specify the period number, group number, subgroup type.

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Knowing the exact "address" of a chemical element - a group, subgroup and period number, one can unambiguously determine the structure of its atom.

Period is a horizontal row of chemical elements. There are seven periods in the modern periodic system. The first three periods small, because they contain 2 or 8 elements:

1st period - H, He - 2 elements;

2nd period - Li ... Ne - 8 elements;

3rd period - Na ... Ar - 8 elements.

Other periods - large. Each of them contains 2-3 rows of elements:

4th period (2 rows) - K ... Kr - 18 elements;

6th period (3 rows) - Cs ... Rn - 32 elements. This period includes a number of lanthanides.

Group is a vertical row of chemical elements. There are eight groups in total. Each group consists of two subgroups: main subgroup And secondary subgroup. For example:

The main subgroup is formed by chemical elements of small periods (for example, N, P) and large periods (for example, As, Sb, Bi).

A side subgroup is formed by chemical elements of only large periods (for example, V, Nb,
Ta).

Visually, these subgroups are easy to distinguish. The main subgroup is “high”, it starts from the 1st or 2nd period. The secondary subgroup is “low”, starting from the 4th period.

So, each chemical element of the periodic system has its own address: period, group, subgroup, ordinal number.

For example, vanadium V is a chemical element of the 4th period, group V, secondary subgroup, serial number 23.

Task 3.1. Specify the period, group and subgroup for chemical elements with serial numbers 8, 26, 31, 35, 54.

Task 3.2. Specify the serial number and name of the chemical element, if it is known that it is located:

a) in the 4th period, group VI, secondary subgroup;

b) in the 5th period, group IV, main subgroup.

How can information about the position of an element in the periodic system be related to the structure of its atom?

An atom is made up of a nucleus (positively charged) and electrons (negatively charged). In general, the atom is electrically neutral.

Positive charge of the nucleus of an atom equal to the atomic number of the chemical element.

The nucleus of an atom complex particle. Almost all the mass of an atom is concentrated in the nucleus. Since a chemical element is a collection of atoms with the same nuclear charge, the following coordinates are indicated near the symbol of the element:

Based on these data, the composition of the nucleus can be determined. The nucleus is made up of protons and neutrons.

Proton p has a mass of 1 (1.0073 amu) and a charge of +1. Neutron n it has no charge (neutral), and its mass is approximately equal to the mass of a proton (1.0087 amu).

The nuclear charge is determined by the protons. And the number of protons is(by size) charge of the nucleus of an atom, i.e. serial number.

Number of neutrons N determined by the difference between the quantities: "mass of the nucleus" A and "serial number" Z. So, for an aluminum atom:

N = A – Z = 27 –13 = 14n,

Task 3.3. Determine composition nuclei of atoms if the chemical element is in:

a) 3rd period, group VII, main subgroup;

b) 4th period, group IV, secondary subgroup;

c) 5th period, group I, main subgroup.

Attention! When determining the mass number of the nucleus of an atom, it is necessary to round off the atomic mass indicated in the periodic system. This is done because the masses of the proton and neutron are practically integer, and the mass of electrons can be neglected.

Let us determine which of the nuclei below belong to the same chemical element:

A (20 R + 20n),

B (19 R + 20n),

IN 20 R + 19n).

Atoms of the same chemical element have nuclei A and B, since they contain the same number protons, i.e., the charges of these nuclei are the same. Studies show that the mass of an atom does not significantly affect its chemical properties.

Isotopes are called atoms of the same chemical element (the same number of protons), which differ in mass (a different number of neutrons).

Isotopes and their chemical compounds differ from each other in physical properties, but the chemical properties of isotopes of one chemical element are the same. Thus, isotopes of carbon-14 (14 C) have the same chemical properties as carbon-12 (12 C), which enter the tissues of any living organism. The difference is manifested only in radioactivity (isotope 14 C). Therefore, isotopes are used to diagnose and treat various diseases, for scientific research.

Let us return to the description of the structure of the atom. As you know, the nucleus of an atom does not change in chemical processes. What is changing? The variable turns out to be total number electrons in an atom and the distribution of electrons. General number of electrons in a neutral atom it is easy to determine - it is equal to the serial number, i.e. charge of the nucleus of an atom:

Electrons have a negative charge of -1, and their mass is negligible: 1/1840 of the mass of a proton.

Negatively charged electrons repel each other and are at different distances from the nucleus. Wherein electrons having an approximately equal amount of energy are located at an approximately equal distance from the nucleus and form an energy level.

The number of energy levels in an atom is equal to the number of the period in which the chemical element is located. Energy levels are conventionally designated as follows (for example, for Al):

Task 3.4. Determine the number of energy levels in the atoms of oxygen, magnesium, calcium, lead.

Each energy level can contain a limited number of electrons:

On the first - no more than two electrons;

On the second - no more than eight electrons;

On the third - no more than eighteen electrons.

These numbers show that, for example, the second energy level can have 2, 5, or 7 electrons, but not 9 or 12 electrons.

It is important to know that regardless of the energy level number on external level(last) cannot be more than eight electrons. The outer eight-electron energy level is the most stable and is called complete. Such energy levels are found in the most inactive elements - the noble gases.

How to determine the number of electrons in the outer level of the remaining atoms? There is a simple rule for this: number of outer electrons equals:

For elements of the main subgroups - the number of the group;

For elements of secondary subgroups, it cannot be more than two.

For example (Fig. 5):

Task 3.5. Specify the number of external electrons for chemical elements with serial numbers 15, 25, 30, 53.

Task 3.6. Find chemical elements in the periodic table, in the atoms of which there is a completed external level.

It is very important to correctly determine the number of external electrons, because It is with them that the most important properties of the atom are associated. Yes, in chemical reactions atoms tend to acquire a stable, complete external level (8 e). Therefore, atoms, on the outer level of which there are few electrons, prefer to give them away.

Chemical elements whose atoms can only donate electrons are called metals. Obviously, there should be few electrons at the outer level of the metal atom: 1, 2, 3.

If there are many electrons on the external energy level of an atom, then such atoms tend to accept electrons before the completion of the external energy level, that is, up to eight electrons. Such elements are called non-metals.

Question. Do the chemical elements of the secondary subgroups belong to metals or non-metals? Why?

Answer. Metals and non-metals of the main subgroups in the periodic table are separated by a line that can be drawn from boron to astatine. Above this line (and on the line) are non-metals, below - metals. All elements of secondary subgroups are below this line.

Task 3.7. Determine whether metals or non-metals include: phosphorus, vanadium, cobalt, selenium, bismuth. Use the position of the element in the periodic table of chemical elements and the number of electrons in the outer level.

In order to compose the distribution of electrons over the remaining levels and sublevels, the following algorithm should be used.

1. Determine the total number of electrons in the atom (by serial number).

2. Determine the number of energy levels (by period number).

3. Determine the number of external electrons (according to the type of subgroup and group number).

4. Indicate the number of electrons at all levels except the penultimate one.

For example, according to points 1–4 for the manganese atom, it is determined:

Total 25 e; distributed (2 + 8 + 2) = 12 e; so, on the third level is: 25 - 12 = 13 e.

The distribution of electrons in the manganese atom was obtained:

Task 3.8. Work out the algorithm by drawing up atomic structure diagrams for elements No. 16, 26, 33, 37. Indicate whether they are metals or non-metals. Explain the answer.

When compiling the above diagrams of the structure of the atom, we did not take into account that the electrons in the atom occupy not only levels, but also certain sublevels each level. Types of sublevels are indicated with Latin letters: s, p, d.

The number of possible sublevels is equal to the level number. The first level consists of one
s-sublevel. The second level consists of two sublevels - s And R. The third level - from three sublevels - s, p And d.

Each sublevel can contain a strictly limited number of electrons:

at the s-sublevel - no more than 2e;

at the p-sublevel - no more than 6e;

at the d-sublevel - no more than 10e.

Sublevels of one level are filled in a strictly defined order: spd.

Thus, R- sublevel can't start to fill if not full s-sublevel of a given energy level, etc. Based on this rule, it is easy to compose the electronic configuration of the manganese atom:

Generally electronic configuration of an atom manganese is written like this:

25 Mn 1 s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 2 .

Task 3.9. Make electronic configurations of atoms for chemical elements No. 16, 26, 33, 37.

Why is it necessary to make electronic configurations of atoms? To determine the properties of these chemical elements. It should be remembered that in chemical processes participate only valence electrons.

Valence electrons are in the outer energy level and incomplete
d-sublevel of the pre-outer level.

Let's determine the number of valence electrons for manganese:

or abbreviated: Mn ... 3 d 5 4s 2 .

What can be determined by the formula for the electronic configuration of an atom?

1. What element is it - metal or non-metal?

Manganese is a metal, because the outer (fourth) level contains two electrons.

2. What process is typical for metal?

Manganese atoms always donate electrons in reactions.

3. What electrons and how many will give a manganese atom?

In reactions, the manganese atom gives up two outer electrons (they are farthest from the nucleus and are weaker attracted by it), as well as five pre-outer d-electrons. The total number of valence electrons is seven (2 + 5). In this case, eight electrons will remain at the third level of the atom, i.e. complete outer level is formed.

All these reasoning and conclusions can be reflected using the scheme (Fig. 6):

The resulting conditional charges of an atom are called oxidation states.

Considering the structure of the atom, in a similar way it can be shown that the typical oxidation states for oxygen are -2, and for hydrogen +1.

Question. With which of the chemical elements can manganese form compounds, if we take into account the degrees of its oxidation obtained above?

Answer: Only with oxygen, tk. its atom has the opposite charge in its oxidation state. The formulas of the corresponding manganese oxides (here the oxidation states correspond to the valences of these chemical elements):

The structure of the manganese atom suggests that manganese cannot have a higher degree of oxidation, because in this case, one would have to touch upon the stable, now completed, pre-outer level. Therefore, the +7 oxidation state is the highest, and the corresponding Mn 2 O 7 oxide is the highest manganese oxide.

To consolidate all these concepts, consider the structure of the tellurium atom and some of its properties:

As a non-metal, the Te atom can accept 2 electrons before the completion of the outer level and donate "extra" 6 electrons:

Task 3.10. Draw the electronic configurations of Na, Rb, Cl, I, Si, Sn atoms. Determine the properties of these chemical elements, the formulas of their simplest compounds (with oxygen and hydrogen).

Practical Conclusions

1. Only valence electrons participate in chemical reactions, which can only be in the last two levels.

2. Metal atoms can only donate valence electrons (all or a few), taking positive oxidation states.

3. Non-metal atoms can accept electrons (missing - up to eight), while acquiring negative oxidation states, and donate valence electrons (all or a few), while they acquire positive oxidation states.

Let us now compare the properties of the chemical elements of one subgroup, for example, sodium and rubidium:
Na...3 s 1 and Rb...5 s 1 .

What is common in the structure of the atoms of these elements? At the outer level of each atom, one electron is active metals. metal activity associated with the ability to donate electrons: the easier an atom gives off electrons, the more pronounced its metallic properties.

What holds electrons in an atom? attraction to the nucleus. The closer the electrons are to the nucleus, the stronger they are attracted by the nucleus of the atom, the more difficult it is to “tear them off”.

Based on this, we will answer the question: which element - Na or Rb - gives away an external electron more easily? Which element is more active metal? Obviously, rubidium, because its valence electrons are farther away from the nucleus (and are less strongly held by the nucleus).

Conclusion. In the main subgroups, from top to bottom, the metallic properties are enhanced, because the radius of the atom increases, and valence electrons are weaker attracted to the nucleus.

Let's compare the properties of chemical elements of group VIIa: Cl …3 s 2 3p 5 and I...5 s 2 5p 5 .

Both chemical elements are non-metals, because. one electron is missing before the completion of the outer level. These atoms will actively attract the missing electron. Moreover, the stronger the missing electron attracts the nonmetal atom, the stronger its manifestations are. non-metallic properties(ability to accept electrons).

What causes the attraction of an electron? Due to the positive charge of the nucleus of the atom. In addition, the closer the electron to the nucleus, the stronger their mutual attraction, the more active the non-metal.

Question. Which element has more pronounced non-metallic properties: chlorine or iodine?

Answer: Obviously, chlorine, because. its valence electrons are closer to the nucleus.

Conclusion. The activity of non-metals in subgroups decreases from top to bottom, because the radius of the atom increases and it is more and more difficult for the nucleus to attract the missing electrons.

Let us compare the properties of silicon and tin: Si …3 s 2 3p 2 and Sn…5 s 2 5p 2 .

Both atoms have four electrons at the outer level. Nevertheless, these elements in the periodic table are on opposite sides of the line connecting boron and astatine. Therefore, for silicon, the symbol of which is above the B–At line, nonmetallic properties are more pronounced. On the contrary, tin, whose symbol is below the B–At line, has stronger metallic properties. This is due to the fact that in the tin atom, four valence electrons are removed from the nucleus. Therefore, the attachment of the missing four electrons is difficult. At the same time, the return of electrons from the fifth energy level occurs quite easily. For silicon, both processes are possible, with the first (acceptance of electrons) predominating.

Conclusions on chapter 3. The fewer external electrons in an atom and the farther they are from the nucleus, the stronger the metallic properties are manifested.

The more external electrons in an atom and the closer they are to the nucleus, the more non-metallic properties are manifested.

Based on the conclusions formulated in this chapter, for any chemical element of the periodic system, you can make a "characteristic".

Property Description Algorithm
chemical element by its position
in the periodic system

1. Draw up a diagram of the structure of the atom, i.e. determine the composition of the nucleus and the distribution of electrons by energy levels and sublevels:

Determine the total number of protons, electrons and neutrons in an atom (by serial number and relative atomic mass);

Determine the number of energy levels (by period number);

Determine the number of external electrons (by type of subgroup and group number);

Indicate the number of electrons at all energy levels except the penultimate one;

2. Determine the number of valence electrons.

3. Determine which properties - metal or non-metal - are more pronounced for a given chemical element.

4. Determine the number of given (received) electrons.

5. Determine the highest and lowest oxidation states of a chemical element.

6. Compose for these oxidation states chemical formulas the simplest compounds with oxygen and hydrogen.

7. Determine the nature of the oxide and write an equation for its reaction with water.

8. For the substances indicated in paragraph 6, draw up equations of characteristic reactions (see Chapter 2).

Task 3.11. According to the above scheme, make descriptions of the atoms of sulfur, selenium, calcium and strontium and the properties of these chemical elements. What are the general properties of their oxides and hydroxides?

If you have completed exercises 3.10 and 3.11, then it is easy to see that not only the atoms of the elements of one subgroup, but also their compounds have common properties and a similar composition.

Periodic law of D.I. Mendeleev:the properties of chemical elements, as well as the properties of simple and complex substances formed by them, are in a periodic dependence on the charge of the nuclei of their atoms.

The physical meaning of the periodic law: the properties of chemical elements are periodically repeated because the configurations of valence electrons (the distribution of electrons of the outer and penultimate levels) are periodically repeated.

So, the chemical elements of the same subgroup have the same distribution of valence electrons and, therefore, similar properties.

For example, the chemical elements of the fifth group have five valence electrons. At the same time, in the atoms of chemical elements of the main subgroups- all valence electrons are in the outer level: ... ns 2 np 3 , where n– period number.

At atoms elements of secondary subgroups only 1 or 2 electrons are in the outer level, the rest are in d- sublevel of the pre-external level: ... ( n – 1)d 3 ns 2 , where n– period number.

Task 3.12. Make brief electronic formulas for atoms of chemical elements No. 35 and 42, and then make up the distribution of electrons in these atoms according to the algorithm. Make sure your prediction comes true.

Exercises for chapter 3

1. Formulate the definitions of the concepts "period", "group", "subgroup". What do the chemical elements that make up: a) period; b) a group; c) subgroup?

2. What are isotopes? What properties - physical or chemical - do isotopes have in common? Why?

3. Formulate periodic law D.I. Mendeleev. Explain it physical meaning and illustrate with examples.

4. What are the metallic properties of chemical elements? How do they change in a group and in a period? Why?

5. What are the non-metallic properties of chemical elements? How do they change in a group and in a period? Why?

6. Make brief electronic formulas of chemical elements No. 43, 51, 38. Confirm your assumptions by describing the structure of the atoms of these elements according to the above algorithm. Specify the properties of these elements.

7. By short electronic formulas

a) ...4 s 2 4p 1 ;

b) …4 d 1 5s 2 ;

at 3 d 5 4s 1

determine the position of the corresponding chemical elements in the periodic system of D.I. Mendeleev. Name these chemical elements. Confirm your assumptions with a description of the structure of the atoms of these chemical elements according to the algorithm. Specify the properties of these chemical elements.

To be continued

The outer energy level of iron, cobalt and nickel atoms has 2 electrons each. At the d-sublevel of the penultimate energy level, iron, cobalt and nickel have 6, 7 and 8 electrons, respectively. The characteristic oxidation states of metals of the iron family are +2 and +3 (compounds are known in which they exhibit an oxidation state of +1, +4 and +6, for example, potassium ferrate K 2 FeO 4, but there are few such compounds and they are not typical). For iron, compounds with an oxidation state (+3) are more stable, and for nickel and cobalt - (+2). Therefore, Fe 2+ is a fairly strong reducing agent, while Ni 2+ and Co 2+ do not have these properties to a noticeable extent, cobalt and nickel compounds are quite stable in air. In the +3 oxidation state, iron, cobalt, nickel exhibit oxidizing properties, the oxidizing capacity increases in the series Fe 3+ - Ni 3+ - Co 3+ .

The properties of iron, cobalt and nickel are very similar to each other (ferromagnetism, catalytic activity, ability to form colored ions, complex formation). However, there are also differences between them: iron in its magnetic properties stands out in the triad, the reducing activity of iron is much greater than that of cobalt and nickel, which, in terms of their electrode potentials, are closer to tin than to iron.

When heated, metals of the iron family interact vigorously with metalloids, for example, with chlorine, bromine, oxygen, sulfur, etc. Chemically pure iron, cobalt and nickel do not change under the influence of air and water. However, ordinary iron contains various impurities, so it corrodes in moist air. The resulting rust layer is brittle and porous; it does not prevent metal from contacting environment and does not protect it from further oxidation. At high temperature iron reacts with water, displacing hydrogen from it. Iron readily dissolves in dilute acids; cobalt, nickel - much more difficult.

At a high concentration of acids in the cold, iron is passivated, becoming covered with a thin film of oxides. The oxides of all three metals (FeO, CoO, NiO) are insoluble in water. Their hydrates are obtained by the action of alkali on soluble salts. Oxide hydrates exhibit basic properties. Fe (OH) 2 hydroxide, interacting with atmospheric oxygen and water, quickly oxidizes:

4Fe (OH) 2 + O 2 + 2H 2 O \u003d 4Fe (OH) 3.

The oxidation of Co 2+ and especially Ni 2+ ions is a little more difficult. Of the oxides and hydroxides of Fe, Co, Ni, only Fe 2 O 3 and Fe (OH) 3 are amphoteric with a predominance of basic properties. The oxides and hydroxides of cobalt and nickel are strong oxidizers; when interacting with acids, they are reduced to divalent metal salts:

Co 2 O 3 + 6HC1 \u003d 2CoC1 2 + Cl 2 + 3H 2 O;

4Ni(OH) 3 + 4H 2 SO 4 = 4NiSO 4 + O 2 + 10H 2 O

Fe 3+ compounds are weak oxidizing agents and, under the action of reducing agents, transform into Fe 2+ derivatives:

H 2 S + Fe 2 (SO 4) 3 = S + 2FeSO 4 + H 2 SO 4

Many simple and complex ions of the elements iron, cobalt and nickel are colored. So, hydrated ions Co 2+ are pink, Ni 2+ are green, Fe 3+ in aqueous solution due to hydrolysis has a brown-yellow color.