The main types of chemical bonds. Chemistry

4. Nature and types of chemical bonds. covalent bond

4.6. Characteristics of a covalent bond

The most important characteristics of a covalent bond are: length l, energy E, directivity, saturation, polarity.

Chemical bond length is the distance between the nuclei of chemically bonded atoms. The longer the bond length, the larger the radii of the interacting atoms. In addition, the bond length depends on its multiplicity: in a series of molecules of the same type, the single bond has the longest bond, and the triple bond has the shortest. The values of chemical bond lengths vary within 0.1–0.3 nm (1 nm = 10 −9 m).

Under chemical bond energy the energy that is released during its formation (or spent to break the bond) is understood. The binding energy is measured in kilojoules per mole. The bond energy is a measure of its strength: the greater the bond energy, the stronger the bond.

The bond energy depends on:

on the multiplicity (in the series single, double, triple bond energy increases);
lengths (the longer the bond, the less the AOs overlap, the weaker it is);
the method of overlapping AO (as already noted, σ-bonds are stronger than π-bonds);
Polarity: As a rule, more polar bonds are stronger.

Example 4.3. Specify the formula of the molecule with the strongest carbon-oxygen bond:

Solution. Let us depict the structural formulas of these molecules:

The strongest carbon-oxygen bond is in the composition of the CO molecule, since in this case it is triple.

Answer: 2).

The energy of covalent bonds is about 100–1000 kJ/mol. The strongest triple bonds are in N 2 (940 kJ/mol) and CO (1076 kJ/mol) molecules.

With an increase in the multiplicity of the bond, its length decreases, and the energy increases

Saturation of a chemical bond means that the ability of a given atom to form covalent bonds is not unlimited, but is limited to a well-defined maximum number. For example, a hydrogen atom can form only one covalent bond, and a carbon atom can form a maximum of four. covalent bonds.

The saturation of a covalent bond is due to a limited number of valence electrons (more precisely, limited valence capabilities, given the formation of bonds by the donor-acceptor mechanism) for a given atom (there is one such electron in a hydrogen atom, and four in a carbon atom).

Orientation of covalent bonds means that each molecule has a certain spatial structure (geometry, stereochemistry). The geometry of a molecule is determined by the bond bond angles, i.e. angles between imaginary straight lines passing through the nuclei of atoms. Each molecule has its own structure, since the interaction of AO, having a certain shape and mutual orientation, is carried out not arbitrarily, but in the direction of their maximum overlap. It is easy to explain the angular shape of the H 2 Se molecule (the s-AO of the H atom overlap with the 4p-AO of the Se atom directed at an angle of 90° relative to each other) and the pyramidal structure of the phosphine PH 3 molecule (the s-AO of the H atom overlap with the 3p-AO of the P atom located along the x, y, z axes):

In table. 4.1 are given structural characteristics(spatial configuration, type of bonds, polarity) of some molecules and ions, as well as substances.

Table 4.1

The structure of some molecules, ions and substances

Formula (name)	Spatial Configuration	Characteristics of bonds, structure of molecules
H 2 O (water)		The molecule has an angular structure (α = 105°), polar (dipole), 2σ-bonds by the exchange mechanism
NH 3 (ammonia)		The molecule has a pyramidal structure (α = 107°), polar (dipole), 3σ-bonds by the exchange mechanism
CO 2 (carbon monoxide (IV))		The molecule has a linear structure 1 (α = 180°), non-polar, 4 bonds (2σ + 2π) by the exchange mechanism
CH 4 (methane)		The molecule has a tetrahedral structure 2 (α = 109°), non-polar, 4σ-bonds by the exchange mechanism
H 2 O 2 (hydrogen peroxide)		The molecule is polar, 3 σ-bonds by the exchange mechanism, 2 of them are polar (Н–О bonds)
P 4 (white phosphorus)		Tetrahedral structure (α = 60°), non-polar molecule, 6 σ-bonds by exchange mechanism
S 8 (rhombic and monoclinic sulfur)		Structure in the form of a "crown", non-polar molecule, 8 σ-bonds by the exchange mechanism
N 2 H 4 (hydrazine)		The molecule is polar, 5 σ-bonds, 4 of them are polar (all by the exchange mechanism)
NH 2 OH (hydroxylamine)		The molecule is polar. 4 σ-bonds (all by exchange mechanism)
CS 2 (carbon disulfide)		The molecule has a linear structure (α = 180°), non-polar, 4 bonds (2σ + 2π), all by the exchange mechanism
COF 2		The molecule is triangular (the nuclei of all atoms are in the same plane), polar, 4 bonds (3σ + 1π), all by the exchange mechanism
SO 2 (sulfur(IV) oxide)		The molecule has an angular structure (α = 120°), polar, 4 bonds (2σ + 2π), all by the exchange mechanism
SO 3 (sulfur oxide (VI))		The molecule has the form of a triangle (α = 120°), all atoms lie in the same plane 4 , non-polar, 6 bonds (3σ + 3π), all by the exchange mechanism
HCN (hydrogen cyanide)		The molecule has a linear structure (α = 180°), polar, 4 bonds (2σ + 2π), all by the exchange mechanism
H 3 O + (hydronium ion)		The ion has a pyramidal structure (like NH 3), α \u003d 107 °, 3 σ-bonds: one according to the donor-acceptor, two - according to the exchange mechanism
NH 4 + (ammonium ion)		The ion has a tetrahedral structure (α = 109°), 4 σ-bonds: one according to the donor-acceptor, three - according to the exchange mechanism
C 6 H 6 (benzene)		The bond angle α is 120°. Molecule non-polar
SiC (Carborundum)		Tetrahedral arrangement of atoms in space 5 (bond angle 109°)
Graphite		In graphite, the C–C bond length is 0.142 nm, the bond angle is 120°
Carbine		Bond angle 180°, carbon - carbon bond length 0.120 nm

Notes: 1. BeH 2 , BeCl 2 , BeF 2 molecules have a linear structure. 2. The molecules SiH 4 , CCl 4 , CF 4 , CBr 4 have a similar structure. 3. The COCl 2 molecule has a similar structure. 4. Plane-triangular structure have molecules BH 3 , BF 3 , BCl 3 . 5. The same spatial arrangement of silicon and diamond atoms (the C–C bond length in diamond is 0.154 nm).

Example 4.4. Draw the electronic formula of the CO 2 molecule.

Solution. The graphic formula of the O=C=O molecule (see Table 4.1). Considering that each bond (regardless of the σ- or π-type) is formed by a pair of electrons, and the oxygen atom has two lone pairs of electrons (of the six valence electrons, only two participate in the formation of bonds with the carbon atom, and four remain, this is just there are two pairs), the electronic formula of CO 2 has the form

You know that atoms can combine with each other to form both simple and complex substances. At the same time, they form various types chemical bonds: ionic, covalent (non-polar and polar), metallic and hydrogen. One of the most essential properties of the atoms of elements, which determine what kind of bond is formed between them - ionic or covalent, - is the electronegativity, i.e. the ability of atoms in a compound to attract electrons to itself.

A conditional quantitative assessment of electronegativity is given by the scale of relative electronegativity.

In periods, there is a general tendency for the growth of the electronegativity of the elements, and in groups - their decline. Electronegativity elements are arranged in a row, on the basis of which it is possible to compare the electronegativity of elements in different periods.

The type of chemical bond depends on how large the difference in the electronegativity values of the connecting atoms of the elements is. The more the atoms of the elements forming the bond differ in electronegativity, the more polar the chemical bond is. It is impossible to draw a sharp boundary between the types of chemical bonds. In most compounds, the type of chemical bond is intermediate; for example, a highly polar covalent chemical bond is close to an ionic bond. Depending on which of the limiting cases is closer in nature to the chemical bond, it is referred to as either an ionic or a covalent polar bond.

Ionic bond.

An ionic bond is formed by the interaction of atoms that differ sharply from each other in electronegativity. For example, typical metals lithium (Li), sodium (Na), potassium (K), calcium (Ca), strontium (Sr), barium (Ba) form an ionic bond with typical non-metals, mainly halogens.

In addition to alkali metal halides, ionic bonds are also formed in compounds such as alkalis and salts. For example, in sodium hydroxide (NaOH) and sodium sulfate (Na 2 SO 4), ionic bonds exist only between sodium and oxygen atoms (the rest of the bonds are covalent polar).

Covalent non-polar bond.

When atoms interact with the same electronegativity, molecules are formed with a covalent non-polar bond. Such a bond exists in the molecules of the following simple substances: H 2 , F 2 , Cl 2 , O 2 , N 2 . Chemical bonds in these gases are formed through common electron pairs, i.e. when the corresponding electron clouds overlap, due to the electron-nuclear interaction, which occurs when the atoms approach each other.

When compiling the electronic formulas of substances, it should be remembered that each common electron pair is a conditional image of an increased electron density resulting from the overlap of the corresponding electron clouds.

covalent polar bond.

During the interaction of atoms, the values of the electronegativity of which differ, but not sharply, there is a shift of the common electron pair to a more electronegative atom. This is the most common type of chemical bond found in both inorganic and organic compounds.

Covalent bonds fully include those bonds that are formed by the donor-acceptor mechanism, for example, in hydronium and ammonium ions.

Metal connection.

The bond that is formed as a result of the interaction of relatively free electrons with metal ions is called a metallic bond. This type of bond is typical for simple substances - metals.

The essence of the process of formation of a metallic bond is as follows: metal atoms easily give up valence electrons and turn into positively charged ions. Relatively free electrons, detached from the atom, move between positive metal ions. Between them there is metallic bond, i.e. Electrons, as it were, cement the positive ions of the crystal lattice of metals.

Hydrogen bond.

A bond that forms between the hydrogen atoms of one molecule and an atom of a strongly electronegative element(O, N, F) another molecule is called a hydrogen bond.

The question may arise: why exactly does hydrogen form such a specific chemical bond?

This is explained by atomic radius very little hydrogen. In addition, when a single electron is displaced or completely donated, hydrogen acquires a relatively high positive charge, due to which the hydrogen of one molecule interacts with atoms of electronegative elements that have a partial negative charge that is part of other molecules (HF, H 2 O, NH 3) .

Let's look at some examples. Usually we represent the composition of water with the chemical formula H 2 O. However, this is not entirely accurate. It would be more correct to denote the composition of water by the formula (H 2 O) n, where n \u003d 2.3.4, etc. This is due to the fact that individual water molecules are interconnected through hydrogen bonds.

Hydrogen bonds are usually denoted by dots. It is much weaker than an ionic or covalent bond, but stronger than the usual intermolecular interaction.

The presence of hydrogen bonds explains the increase in the volume of water with decreasing temperature. This is due to the fact that as the temperature decreases, the molecules become stronger and therefore the density of their “packing” decreases.

When studying organic chemistry The following question also arose: why are the boiling points of alcohols much higher than those of the corresponding hydrocarbons? This is explained by the fact that hydrogen bonds are also formed between alcohol molecules.

An increase in the boiling point of alcohols also occurs due to the enlargement of their molecules.

The hydrogen bond is also characteristic of many other organic compounds (phenols, carboxylic acids, etc.). From courses in organic chemistry and general biology, you know that the presence of a hydrogen bond explains the secondary structure of proteins, the structure of the double helix of DNA, i.e., the phenomenon of complementarity.

According to the nature of the distribution of electron density in a molecule, chemical bonds are divided into covalent, ionic, metallic.

1. covalent bond - a chemical bond between two atoms, carried out by a common pair of electrons for these atoms.

There are three mechanisms for the formation of a covalent bond: exchange, donor-acceptor and dative.

In the exchange mechanism, a covalent bond is formed by two electrons with oppositely directed spins and belonging to different atoms.

The donor-acceptor mechanism for the formation of a covalent bond occurs when one of the atoms (donor) represents a pair of electrons for the bond, and the other (acceptor) represents a vacant orbital.

If the atoms that form a bond simultaneously perform the functions of both a donor and an acceptor, then one speaks of a dative mechanism for the formation of a covalent bond.

To assess the ability of an atom of a given element to attract electrons to itself, making a bond, use the value of relative electronegativity ( EO). When a covalent bond is formed between atoms of different elements, the electron cloud shifts to an atom with a large value EO. The greater the difference in electronegativity, the greater the polarity of the bond. The displacement of the common electron cloud causes the negative charge density to be higher near a more electronegative atom and lower near a less electronegative atom. Thus, the first atom acquires an excess negative charge, and the second atom acquires an excess positive charge of the same absolute value. Such charges are called efficient . A system of two equal in magnitude but opposite in sign charges located at a certain distance from each other is called electric dipole . Dipole moment of bond  (Clm) is determined from the ratio

 = ql,

where q is the absolute value of the charge, C; l is the length of the dipole, m (vector directed from the center of the positive charge to the center of the negative charge).

Debye serves as an off-system unit for measuring the value of the dipole moment (1D = 3.3310 -30 Cm).

The dipole moment of a polyatomic molecule is considered as the vector sum of the bond dipole moments, i.e. it depends not only on the polarities of the bonds, but also on their mutual arrangement.

The triatomic AB 2 molecule can have a linear (a) or angular (b) structure:

The four-atomic AB 3 molecule can be built in the form of a regular triangle (c), a trigonal pyramid (d), or in a T-shaped

form (d).

AB 4 molecules can have a tetrahedral and square structure.

In linear AB 2, triangular AB 3, tetrahedral and square AB 4 molecules, the dipole moments of the A–B bonds mutually compensate each other, so that the total dipole moments are zero, i.e., such molecules are nonpolar, despite the polarity of individual bonds.

In angular, pyramidal, and T-shaped molecules, compensation of the dipole moments of individual bonds does not occur; the dipole moments of such molecules are not equal to zero.

To predict the geometric structure of molecules, the idea of hybridization of atomic orbitals (AO) of the central atom (CA) is used.

Hybridization is the averaging of the AO energies of the central atom before the chemical interaction, which leads to the formation of hybrid orbitals directed towards the formed bond. Due to this, the overlap of the CA electron clouds and interacting atoms increases, which leads to the strengthening of the chemical bond.

The number of hybrid AOs is equal to the number of initial AOs involved in hybridization. So, if one s- and one p-orbitals participate in hybridization (sp-hybridization), then two equivalent sp-orbitals are formed; from one s- and two p-orbitals (sp 2 -hybridization) three sp 2 -orbitals are formed

Each type of AO hybridization corresponds to a certain geometric shape of the molecule:

2. Ionic bond - the result of the electrostatic interaction of oppositely charged ions with separate electron shells. This bond can be considered as the limiting case of the polarity of a chemical covalent bond, which corresponds to a significant shift of a pair of bond electrons to the most electronegative atom. The larger this shift, the closer the bond is to a purely ionic one.

3. Hydrogen bond occurs when a hydrogen atom bonded to atoms of a strongly electronegative element is capable of forming another chemical bond. The presence of hydrogen bonds leads to a noticeable polymerization of water, hydrogen fluoride, and many organic compounds.

In substances with a molecular structure, intermolecular interaction. The forces of intermolecular interaction, also called forces Van der Waals , are weaker than the forces leading to the formation of a covalent bond, but they appear on long distances. The main role in their formation is played by the interaction of molecular dipoles.

Example 1 Which of the connections H – N, H – S, H – Te, H – Li most polar? To which of the atoms is the electron cloud shifted in each of the given examples?

Solution. To determine the nature of the bond, it is necessary to find the difference in electronegativity ( EO) in these pairs of atoms:

a)  EO H - N = 3,0 – 2,1 = 0,9;

b)  EO H - S = 2,5 – 2,1 = 0,4;

c)  EO H - Te = 2,1 – 2,1 = 0;

d)  EO H - Li = 2,1 – 1,0 = 1,1.

The more  EO the more polar the bond. The most polar bond H – Li. The electron cloud is shifted towards the atom with higher electronegativity, i.e. towards nitrogen in the first example, sulfur in the second and hydrogen in the fourth. In the third example, the connection H – Te is not polar, the electron cloud is at an equal distance from hydrogen and tellurium.

Example 2 What valency can fluorine and chlorine atoms exhibit in their compounds?

Solution. Both elements F and Cl, are located in the VII A group, are electronic analogues and have the structure of the external energy level n s2 n p 5 . But for the fluorine atom, the second energy level is external, which has only 2 sublevels: s- and p-, while the external electrons of the chlorine atom occupy the third energy level, which contains the d- sublevel:

9 F 17 Cl

2s 2 2p 5 3s 2 3p 5 3d

The valency of both elements, determined by the number of unpaired electrons, in unexcited atoms is 1. But upon excitation, the electrons of chlorine atoms can transfer to free 3 d-orbitals, and, accordingly, the valency of this element can be equal to 3, 5, 7:

Example 3 Explain the mechanism of formation of a molecule SiF 4 and ion SiF 6 2 - . Can an ion exist? CF 6 2 - ?

Solution. The electronic configuration of the silicon atom is 1s 2 2s 2 2p 6 3s 2 3p 2 . The electronic structure of its external energy level can be represented by the following graphical diagram:

When excited, the silicon atom goes into the state 1s 2 2s 2 2p 6 3s 1 3p 3 , and the electronic state of its outer energy level corresponds to the scheme

Four unpaired electrons of an excited atom can participate in the formation of four covalent bonds by the exchange mechanism with fluorine atoms having one paired electron each, with the formation of a molecule SiF 4 .

To form an ion SiF 6 2- to the molecule SiF 4 two ions must join F - (1s 2 2s 2 2p 6), all of whose ions are paired. The bond in this case is carried out according to the donor-acceptor mechanism due to a pair of electrons of fluoride ions and two vacant 3d orbitals of the silicon atom.

And he CF 6 2- cannot be formed, because carbon, as an element of the second period, does not have free d-orbitals that could be electron pair acceptors.

Example 4 The dipole moment of the ammonia molecule is 1.48 D. Calculate the length of the dipole. Can we assume that the molecule has the shape of a regular triangle?

Solution.

 = 1.48 D = 1.483.3310 -30 Cm = 4.9310 -30 Cm;

q= 1.6010 -19 Cl.

dipole length,
m = 0.0308 nm.

Molecule NH 3 cannot have the shape of a regular triangle, since in this case its dipole moment would be equal to zero. This molecule is built in the form of a trigonal pyramid, at the top of which there is a nitrogen atom, and at the tops of the base there are hydrogen atoms.

What is the nature of bonds in molecules NCl 3 , CS 2 , ICl 5 , NF 3 , OF 2 , ClF, CO 2 ? Indicate for each of them the direction of displacement of the common electron pair.

Explain why the maximum valence of phosphorus can be equal to five, while nitrogen does not have such a valence state.

H – O – X, (where X -Cl, Br, I) and determine: a) which of the bonds in each molecule is characterized by a greater degree of ionicity; b) what is the nature of the dissociation of molecules in an aqueous solution.

Based on the difference in the electronegativity of the atoms of the elements, indicate how the degree of bond ionicity in compounds changes HF, HCl, HBr, HI.

Determine in which of the oxides of the elements of the third period of the periodic system of elements D.I. Mendeleev connection E - O approaches ionic.

Compare the ways in which covalent bonds are formed in molecules CH 4 , NH 3 and in ion NH 4 + . Can ions exist? CH 5 + and NH 5 2+ ?

Which atom or ion is an electron pair donor in the formation of an ion BH 4 - ?

The ionization energies of fluorine and chlorine atoms are 17.4 and 13.0 eV, respectively. Which of these elements is most likely to form ionic compounds?

Calculate the difference in the relative electronegativity of atoms for bonds H – O and O – As. Which bond is more polar? What type of hydroxide is As(Oh) 3 ?

What valency can sulfur show in its compounds? What is the structure of the external electronic level of sulfur in the normal and excited states?

Determine the polarity of the molecule HBr, if the length of the dipole of the molecule is 0.1810 -10 m.

The dipole length of a hydrogen fluoride molecule is 410 -11 m. Calculate its dipole moment in debyes and in coulomb meters.

Dipole moments of molecules H 2 O and H 2 S are equal to 1.84 and 0.94 D, respectively. Calculate the lengths of the dipoles. In which molecule is the bond more polar? Indicate the directions of dipole moments of bonds in these molecules.

Dipole moment of a molecule CS 2 equals zero. What type of carbon AO hybridization describes the formation of this molecule?

According to the data below for compounds with sp-, sp 2 - and sp 3-hybridization of electron clouds, establish in which case the connection will be the strongest.

Dipole moments of molecules bf 3 and NF 3 are equal to 0 and

0.2 D. What types of hybridizations of boron and nitrogen AO describe the formation of this molecule?

What type of hybridization of electron clouds in molecules BeH 2 , SiH 4 , CS 2 , BBr 3 ? What is the spatial configuration of these molecules?

What hybrid clouds of a carbon atom are involved in the formation of a chemical bond in molecules CCl 4 , CO 2 , COCl 2 ?

What is the reason for the different spatial structure of molecules BCl 3 and NH 3 ?

Specify the type of silicon AO hybridization in molecules SiH 4 and SiF 4 . Are these molecules polar?

What shape can molecules like AB 2 have? Look at examples of molecules BeCl 2 , ZnBr 2 , CO 2 , H 2 O.

What type of hybridization takes place during the formation of molecules NH 3 and H 2 O? What explains the change in the angle H -N- H and N - O - N compared with the value of the bond angle corresponding to this type of hybridization?

in molecules SO 2 and SO 3 the sulfur atom is in a state of sp 2 hybridization. Are these molecules polar? What is their spatial structure?

When interacting SiF 4 With HF a strong acid is formed H 2 SiF 6 , dissociating into ions H + and SiF 6 2 - . Can a reaction proceed in this way? CF 4 and HF?

Task number 1

From the proposed list, select two compounds in which there is an ionic chemical bond.

1. Ca(ClO 2) 2
2. HClO 3
3.NH4Cl
4. HClO 4
5.Cl2O7

Answer: 13

In the vast majority of cases, the presence of an ionic type of bond in a compound can be determined by the fact that its structural units simultaneously include atoms of a typical metal and non-metal atoms.

On this basis, we establish that there is an ionic bond in compound number 1 - Ca(ClO 2) 2, because in its formula, one can see atoms of a typical calcium metal and atoms of non-metals - oxygen and chlorine.

However, there are no more compounds containing both metal and non-metal atoms in this list.

Among the compounds indicated in the assignment there is ammonium chloride, in which the ionic bond is realized between the ammonium cation NH 4 + and the chloride ion Cl − .

Task number 2

From the proposed list, select two compounds in which the type of chemical bond is the same as in the fluorine molecule.

1) oxygen

2) nitric oxide (II)

3) hydrogen bromide

4) sodium iodide

Write down the numbers of the selected connections in the answer field.

Answer: 15

The fluorine molecule (F 2) consists of two atoms of one non-metal chemical element, therefore the chemical bond in this molecule is covalent non-polar.

A covalent non-polar bond can only be realized between atoms of the same chemical element of a non-metal.

Of the proposed options, only oxygen and diamond have a covalent non-polar type of bond. The oxygen molecule is diatomic, consists of atoms of one chemical element of a non-metal. Diamond has an atomic structure and in its structure each carbon atom, which is a non-metal, is bonded to 4 other carbon atoms.

Nitric oxide (II) is a substance consisting of molecules formed by atoms of two different non-metals. Since the electronegativity of different atoms is always different, the shared electron pair in the molecule is shifted towards the more electronegative element, in this case oxygen. Thus, the bond in the NO molecule is covalent polar.

Hydrogen bromide also consists of diatomic molecules made up of hydrogen and bromine atoms. The shared electron pair forming the H-Br bond is shifted to the more electronegative bromine atom. The chemical bond in the HBr molecule is also covalent polar.

Sodium iodide is an ionic substance formed by a metal cation and an iodide anion. The bond in the NaI molecule is formed due to the transfer of an electron from 3 s-orbitals of the sodium atom (the sodium atom turns into a cation) to an underfilled 5 p-orbital of the iodine atom (the iodine atom turns into an anion). Such a chemical bond is called ionic.

Task number 3

From the proposed list, select two substances between the molecules of which hydrogen bonds are formed.

1. C 2 H 6
2.C2H5OH
3.H2O
4. CH 3 OCH 3
5. CH 3 COCH 3

Write down the numbers of the selected connections in the answer field.

Answer: 23

Explanation:

Hydrogen bonds take place in substances molecular structure, in which there are covalent H-O bonds, H-N, H-F. Those. covalent bonds of the hydrogen atom with the atoms of the three chemical elements with the highest electronegativity.

Thus, obviously, there are hydrogen bonds between molecules:

2) alcohols

3) phenols

4) carboxylic acids

5) ammonia

6) primary and secondary amines

7) hydrofluoric acid

Task number 4

From the proposed list, select two compounds with an ionic chemical bond.

1. PCl 3
2.CO2
3.NaCl
4. H 2 S
5. MgO

Write down the numbers of the selected connections in the answer field.

Answer: 35

Explanation:

In the overwhelming majority of cases, it can be concluded that there is an ionic type of bond in a compound by the fact that the composition of the structural units of a substance simultaneously includes atoms of a typical metal and non-metal atoms.

On this basis, we establish that there is an ionic bond in compound number 3 (NaCl) and 5 (MgO).

Note*

In addition to the above feature, the presence of an ionic bond in a compound can be said if its structural unit contains an ammonium cation (NH 4 +) or its organic analogs - cations of alkylammonium RNH 3 + , dialkylammonium R 2 NH 2 + , trialkylammonium R 3 NH + or tetraalkylammonium R 4 N + , where R is some hydrocarbon radical. For example, the ionic type of bond takes place in the compound (CH 3) 4 NCl between the cation (CH 3) 4 + and the chloride ion Cl - .

Task number 5

From the proposed list, select two substances with the same type of structure.

4) table salt

Write down the numbers of the selected connections in the answer field.

Answer: 23

Task number 8

From the proposed list, select two substances of non-molecular structure.

2) oxygen

3) white phosphorus

5) silicon

Write down the numbers of the selected connections in the answer field.

Answer: 45