D element 4 of the period of the periodic system corresponds. General characteristics of d-elements

This article is missing links to sources of information. Information must be verifiable, otherwise it can be questioned and removed. You can ... Wikipedia

Period is a line of the periodic table of chemical elements, a sequence of atoms according to increasing nuclear charge and filling the outer electron shell with electrons. The periodic table has seven periods. The first period containing 2 elements ... Wikipedia

104 Lawrence ← Rutherfordium → Dubnium ... Wikipedia

DI Mendeleev, the natural classification of chemical elements, which is a tabular (or other graphic) expression of Mendeleev's periodic law (See Mendeleev's periodic law). P. s. e. developed by D.I.Mendeleev in 1869 ... ... Great Soviet Encyclopedia

Dmitry Mendeleev- (Dmitry Ivanovich Mendeleyev) Biography of Mendeleev, scientific activity of Mendeleyev Information about the biography of Mendeleev, scientific activity of Mendeleyev Contents Contents 1. Biography 2. Member of the Russian people 3. Scientific activity Periodic ... Investor encyclopedia

Periodic table of chemical elements (periodic table) classification of chemical elements, establishing the dependence of various properties of elements on the charge of the atomic nucleus. The system is a graphic expression of the periodic law, ... ... Wikipedia

Chemical elements (periodic table) classification of chemical elements, establishing the dependence of various properties of elements on the charge of the atomic nucleus. The system is a graphic expression of the periodic law established by the Russian ... ... Wikipedia

DEFINITION

Potassium- the first element of the fourth period. It is located in group I of the main (A) subgroup of the Periodic Table.

Refers to elements of the s - family. Metal. The metal elements included in this group are collectively referred to as alkaline. Designation - K. Serial number - 19. Relative atomic mass - 39.102 amu.

The electronic structure of the potassium atom

A potassium atom consists of a positively charged nucleus (+19), inside which there are 19 protons and 20 neutrons, and around, in 4 orbits, 19 electrons move.

Fig. 1. Schematic structure of the potassium atom.

The orbital distribution of electrons is as follows:

1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 .

The external energy level of a potassium atom contains 1 electron, which is valence. The oxidation state of potassium is +1. The energy diagram of the ground state takes the following form:

Excited state despite vacancies 3 p- and 3 d- no orbitals.

Examples of problem solving

EXAMPLE 1

Exercise

An atom of an element has the following electronic configuration 1 s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 3. Indicate: a) the charge of the nucleus; b) the number of completed energy levels in the electron shell of this atom; c) the highest possible oxidation state; d) the valence of the atom in conjunction with hydrogen.

Solution

In order to answer the questions posed, you first need to determine the total number of electrons in an atom of a chemical element. This can be done by adding up all the electrons present in the atom, disregarding their distribution over energy levels:

2+2+6+2+6+10+2+3 = 33.

This is arsenic (As). Now let's answer the questions:

a) the charge of the nucleus is +33;

b) the atom has four levels, of which three are complete;

c) we write down the energy diagram for the valence electrons of the arsenic atom in the ground state.

Arsenic is capable of going into an excited state: electrons s- the sublevels are steamed and one of them goes to the vacant one d-orbital.

Five unpaired electrons indicate that the maximum possible oxidation state of arsenic is +5;

d) The valency of arsenic in combination with hydrogen is III (AsH 3).

The purpose of this work is to study the chemical properties of some transition metals and their compounds.

Metals of side subgroups, the so-called transition elements, belong to d - elements, since in their atoms they are filled with d - orbital electrons.

In transition metals, valence electrons are located on the d - orbital of the pre-external level and S - orbital of the external electronic level. The metallicity of the transition elements is explained by the presence of one or two electrons in the outer electron layer.

The incomplete d-sublevel of the pre-outer electron layer causes a variety of valence states of metals of side subgroups, which in turn explains the existence of a large number of their compounds.

The electrons of the d - orbitals are involved in chemical reactions after the S - electrons of the outer orbital are used up. All or part of the electrons of the d - orbitals of the penultimate electronic level can participate in the formation of chemical compounds. In this case, compounds are formed corresponding to different valence states. The variable valence of transition metals is their characteristic property (with the exception of metals of II and III side subgroups). Metals of the side subgroups IV, V, VI, VII of groups can be included in the composition of compounds both in the highest valence state (which corresponds to the group number) and in lower valence states. So, for example, titanium is characterized by 2-, 3-, 4-valence states, and for manganese 2-, 3-, 4-, 6- and 7-valence states.

Oxides and hydroxides of transition metals, in which the latter are in the lowest valence state, usually exhibit basic properties, for example, Fe (OH) 2. Higher oxides and hydroxides are characterized by amphoteric properties, for example TiO 2, Ti (OH) 4, or acidic, for example
and
.

The redox properties of the compounds of the metals under consideration are also associated with the valence state of the metal. Compounds with the lowest oxidation state usually exhibit reducing properties, while those with the highest oxidation state exhibit oxidizing properties.

For example, for manganese oxides and hydroxides, the redox properties change as follows:

Complex compounds.

A characteristic feature of transition metal compounds is the ability to form complexes, which is explained by the presence of a sufficient number of free orbitals in the external and pre-external electronic levels of metal ions.

In the molecules of such compounds, a complexing agent is located in the center. Around it, ions, atoms or molecules called ligands are coordinated. Their number depends on the properties of the complexing agent, its degree of oxidation and is called the coordination number:

The complexing agent coordinates two types of ligandrs around itself: anionic and neutral. Complexes are formed when several different molecules combine into one more complex:

copper (II) sulfotetraamine potassium hexacyanoferrate (III).

In aqueous solutions, complex compounds dissociate, forming complex ions:

The complex ions themselves are also capable of dissociation, but usually to a very small extent. For instance:

This process is reversible and its balance is sharply shifted to the left. Therefore, according to the law of mass action,

The constant Kn in such cases is called the constant of instability of complex ions. The larger the value of the constant, the stronger the ability of the ion to dissociate into its constituent parts. Kn values are given in the table:

Experiment 1. Oxidation of Mn 2+ ions into ions
.

Pour a little lead dioxide into the tube so that only the bottom of the tube is covered, add a few drops of concentrated
and one drop of solution
... Heat the solution and observe the appearance of ions
... Write the reaction equation. A solution of manganese salt should be taken in a small amount, since an excess of ions
restores
before
.

Experiment 2. Oxidation by ions
in acidic, neutral and alkaline solutions.

Ion reduction products
are different and depend on the pH of the solution. So, in acidic solutions, the ion
reduced to ions
.

In neutral, weakly acidic and weakly alkaline solutions, i.e. in the range of pH from 5 to 9, ion
reduced to form permanganous acid:

In strongly alkaline solutions and in the absence of a reducing agent, the ion
reduced to ion
.

Pour 5-7 drops of potassium permanganate solution into three test tubes
... Add the same volume of diluted sulfuric acid to one of them, add nothing to the other, and add a concentrated alkali solution to the third. Add to all three test tubes drop by drop, shaking the contents of the test tube, a solution of potassium or sodium sulfite until the solution becomes discolored in the first test tube, a brown precipitate appears in the second, and the solution turns green in the third. Write the reaction equation, keeping in mind that the ion
turns into ions
... Give an estimate of the oxidative capacity
in various environments according to the table of redox potentials.

Experience 3. Interaction of potassium permanganate with hydrogen peroxide. Place 1 ml in a test tube. hydrogen peroxide, add a few drops of sulfuric acid solution and a few drops of potassium permanganate solution. What gas is emitted? Test it with a smoldering torch. Write a reaction equation and explain it in terms of redox potentials.

Experience 4. Complex compounds of iron.

A) Obtaining Prussian blue. To 2-3 drops of iron (III) salt solution, add a drop of acid, a few drops of water and a drop of a solution of hexation - (P) potassium ferrate (yellow blood salt). Watch the Prussian Blue sediment appear. Write the reaction equation. This reaction is used to detect ions
... If
taken in excess, its colloidal soluble form can be formed instead of the Prussian blue sediment.

Explore the relationship of Prussian Blue to alkali. What is being observed? Which dissociates better. Fe (OH) 2 or complex ion
?

B) Obtaining iron thiocyanate III. Add a drop of potassium or ammonium thiocyanate solution to a few drops of iron salt solution
... Write the reaction equation.

Explore the Thiocyanate Attitude
to alkalis and explain the observed phenomenon. This reaction, like the previous one, is used to detect the ion
.

Experience 5. Obtaining a complex compound of cobalt.

Place in a test tube 2 drops of a saturated solution of cobalt salt and add 5-6 drops of a saturated solution of ammonium: take into account that this forms a solution of a complex salt
... Complex ions
colored blue, and hydrated ions
- in pink. Describe the observed phenomena:

1. Equation of obtaining complex cobalt salt.

2. Equation of dissociation of complex cobalt salt.

3. Equation of dissociation of a complex ion.

4. Expression of the constant of instability of a complex ion.

Test questions and tasks.

1. What properties (oxidizing or reducing) do compounds with the highest oxidation state of an element exhibit? Write down the electron-ion and molecular reaction equation:

2. What properties are shown by compounds with an intermediate oxidation state of an element? Make up the electron-ion and molecular reaction equations:

3. Indicate the distinctive and similar properties of iron, cobalt, nickel. Why did D.I.Mendeleev place cobalt between iron and nickel in the periodic table of elements, despite the value of its atomic weight?

4. Write the formulas of complex compounds of iron, cobalt, nickel. What explains the good complexing ability of these elements?

5. How does the character of manganese oxides change? What is the reason for this? What oxidation numbers can manganese have in compounds?

6. Are there any similarities in the chemistry of manganese and chromium? How is it expressed.

7. On what properties of manganese, iron, cobalt, nickel, chromium is their application in technology based?

8. Give an estimate of the oxidizing ability of ions
and reducing ability of ions
.

9. How to explain that the oxidation numbers of Cu, Ag, Au are more than +17.

10. Explain the blackening of silver over time in air, greening of copper in air.

11. Make an equation of the reactions proceeding according to the scheme.

Elements of the 4th period of the Periodic Table

n eh	Element electronic configuration	KR	t pl, o C	D N pl, kJ / mol	HB, MPa	t kip, o C	D N bale, kJ / mol
	K	s 1	Bcc	63,55	2,3	-		89,4
	Ca	s 2	HCC		8,4
	Sc	s 2 d 1	Hex.		14,1
	Ti	s 2 d 2	GPU
	V	s 2 d 3	Bcc		23,0
	Cr	s 1 d 5	Bcc		21,0
	Mn	s 2 d 5	Bcc		12,6	-
	Fe	s 2 d 6	Bcc		13,77
	Co	s 2 d 7	Hex.		16,3
	Ni	s 2 d 8	HCC		17,5
	Cu	s 1 d 10	HCC		12,97
	Zn	s 2 d 10	GPU	419,5	7,24	-
	Ga	s 2 d 10 p 1	Rhombus.	29,75	5,59
	Ge	s 2 d 10 p 2	PC	958,5		-
	As	s 2 d 10 p 3	Hex.		21,8	-	Subl.
	Se	s 2 d 10 p 4	Hex.		6,7		685,3
	Br	s 2 d 10 p 5		-7,25	10,6	-	59,8	29,6
	Kr	s 2 d 10 p 6		-157	1,64	-	-153	9,0

Table 3.4 and fig. 3.8 shows data on changes in some physical and chemical characteristics of simple substances of the fourth period of the table D.I. Mendeleev (the first period containing d-elements) based on the number of external electrons. All of them are associated with the energy of interaction between atoms in the condensed phase and regularly change in the period. The nature of the change in the characteristics of the number of electrons at the external level makes it possible to single out individual regions the region of increase (approximately 1-6), the region of relative constancy (6-10), the region of decreasing values (10-13), an abrupt increase (14) and a monotonic decrease ( 14-18).

Rice. 3.8. Melting temperature dependence ( t pl) and boiling ( t kip), enthalpy of melting (D N pl) and boiling (D N kip), the Brinell hardness of simple substances of the 4th period on the number of electrons at the external energy level (the number of electrons in excess of the completely filled shell of the noble gas Ar)

As noted, the valence bond method can be used to describe the chemical bond between metal atoms. The approach to the description can be illustrated by the example of a potassium crystal. The potassium atom has one electron at the external energy level. In an isolated potassium atom, this electron is located at 4 s-orbital. At the same time, the potassium atom contains not very different in energy from 4 s-orbitals are free, not occupied by electrons, orbitals belonging to 3 d, 4p-sub-levels. It can be assumed that during the formation of a chemical bond, the valence electron of each atom can be located not only at 4 s-orbitals, but also in one of the free orbitals. One valence electron of an atom allows it to realize one single bond with the nearest neighbor. The presence in the electronic structure of the atom of free orbitals slightly differing in energy suggests that the atom can `` capture '' an electron from its neighbor to one of the free orbitals and then it will be able to form two single bonds with the nearest neighbors. Due to the equality of the distances to the nearest neighbors and the indistinguishability of atoms, various variants of the realization of chemical bonds between neighboring atoms are possible. If we consider a fragment of the crystal lattice of four neighboring atoms, then the possible options are shown in Fig. 3.9.

Elements of the 4th period of the Periodic Table - concept and types. Classification and features of the category "Elements of the 4th period of the Periodic table" 2015, 2017-2018.

Concept transition element commonly used to refer to any element with d- or f-valence electrons. These elements occupy a transitional position in the periodic table between electropositive s-elements and electronegative p-elements.

d-Elements are usually called the main transition elements. Their atoms are characterized by internal building up of d-subshells. The point is that the s-orbital of their outer shell is usually filled before the filling of the d-orbitals in the previous electron shell begins. This means that each new electron added to the electron shell of the next d-element, in accordance with the filling principle, falls not on the outer shell, but on the inner subshell preceding it. The chemical properties of these elements are determined by the participation of electrons in the reactions of both of these shells.

d-Elements form three transitional rows - in the 4th, 5th and 6th periods, respectively. The first transition series contains 10 elements, from scandium to zinc. It is characterized by internal building up of 3d orbitals. 4s orbital fills up earlier than 3d orbital, because it has less energy (Klechkovsky's rule).

However, the existence of two anomalies should be noted. Chromium and copper have only one electron in their 4s orbitals. This is because semi-filled or fully-filled subshells are more stable than partially filled subshells.

The chromium atom has one electron in each of the five 3d orbitals that form the 3d subshell. This subshell is half full. The copper atom has a pair of electrons in each of the five 3d orbitals. A similar anomaly is observed for silver.

All d-elements are metals.

Electronic configurations of elements of the fourth period from scandium to zinc:

Chromium

Chromium is in the 4th period, in the VI group, in a secondary subgroup. It is a medium active metal. In its compounds, chromium exhibits oxidation states +2, +3 and +6. CrO is a typical basic oxide, Cr 2 O 3 is an amphoteric oxide, CrO 3 is a typical acidic oxide with the properties of a strong oxidizing agent, that is, an increase in the oxidation state is accompanied by an increase in acidic properties.

Iron

Iron is in the 4th period, in the VIII group, in a side subgroup. Iron is a metal of medium activity; in its compounds it exhibits the most characteristic oxidation states of +2 and +3. Iron compounds are also known, in which it exhibits an oxidation state of +6, which are strong oxidizing agents. FeO exhibits basic, and Fe 2 O 3 - amphoteric with a predominance of basic properties.

Copper

Copper is in the 4th period, in the 1st group, in the secondary subgroup. Its most stable oxidation states are +2 and +1. In the series of metal voltages, copper is found after hydrogen; its chemical activity is not very high. Copper oxides: Cu2O CuO. The latter and copper hydroxide Cu (OH) 2 exhibit amphoteric properties with a predominance of basic ones.

Zinc

Zinc is in the 4th period, in group II, in a secondary subgroup. Zinc belongs to metals of average activity, in its compounds it exhibits the only oxidation state +2. Zinc oxide and hydroxide are amphoteric.