The chemical bond in the fluorine molecule is ionic. Types of chemical bonds. Covalent chemical bond
Chemistry preparation for cancer and DPA
Comprehensive edition
PART AND
GENERAL CHEMISTRY
CHEMISTRY OF ELEMENTS
HALOGENS
Simple substances
Chemical properties of fluorine
Fluorine is the strongest oxidizing agent in nature. It does not react directly only with helium, neon and argon.
During the reaction with metals, fluorides, ionic compounds, are formed:
Fluorine reacts vigorously with many nonmetals, even with some inert gases:
Chemical properties of Chlorine. Interaction with complex substances
Chlorine is a stronger oxidizer than bromine or iodine, so chlorine displaces heavy halogens from their salts:
Dissolving in water, chlorine partially reacts with it, resulting in the formation of two acids: chloride and hypochlorite. In this case, one Chlorine atom increases the oxidation state, and the other atom decreases it. Such reactions are called disproportionation reactions. Disproportionation reactions are self-healing-self-oxidation reactions, i.e. reactions in which one element exhibits the properties of both an oxidizer and a reducing agent. During disproportionation, compounds are simultaneously formed in which the element is in a more oxidized and reduced state compared to the original one. The oxidation state of the Chlorine atom in the hypochlorite acid molecule is +1:
The interaction of chlorine with alkali solutions proceeds similarly. In this case, two salts are formed: chloride and hypochlorite.
Chlorine interacts with various oxides:
Chlorine oxidizes some salts in which the metal is not in its maximum oxidation state:
Molecular chlorine reacts with many organic compounds. In the presence of ferrum(III) chloride as a catalyst, chlorine reacts with benzene to form chlorobenzene, and when irradiated with light, the same reaction results in the formation of hexachlorocyclohexane:
Chemical properties bromine and iodine
Both substances react with hydrogen, fluorine and alkalis:
Iodine is oxidized by various strong oxidizing agents:
Methods for extracting simple substances
Fluoride extraction
Since fluorine is the strongest chemical oxidizer, it is impossible to isolate it using chemical reactions from compounds in free form, and therefore fluorine is extracted by the physicochemical method - electrolysis.
To extract fluorine, potassium fluoride melt and nickel electrodes are used. Nickel is used due to the fact that the metal surface is passivated by fluorine due to the formation of insoluble
NiF2, therefore, the electrodes themselves are not destroyed by the substance that is released on them:Chlorine extraction
Chlorine is produced on an industrial scale by electrolysis of a sodium chloride solution. As a result of this process, sodium hydroxide is also produced:
In no large quantities Chlorine is produced from the oxidation of hydrogen chloride solution using various methods:
Chlorine is a very important product of the chemical industry.
Its global production amounts to millions of tons.
Extracts of bromine and iodine
For industrial use, bromine and iodine are obtained from the oxidation of bromides and iodides, respectively. For oxidation, molecular chlorine, concentrated sulfate acid or manganese dioxide are most often used:
Fluorine and some of its compounds are used as an oxidizer for rocket fuel. Large quantities of fluorine are used to extract various refrigerants (freons) and some polymers that are characterized by chemical and thermal resistance (Teflon and some others). Fluorine is used in nuclear technology to separate uranium isotopes.
Most chlorine is used to produce hydrochloric acid, and also as an oxidizing agent for the production of other halogens. In industry it is used to bleach fabrics and paper. In larger quantities than fluorine, it is used for the production of polymers (PVC and others) and refrigerants. Chlorine is used to disinfect drinking water. It is also needed for the extraction of certain solvents, such as chloroform, methylene chloride, and carbon tetrachloride. It is also used for the production of many substances, such as potassium chlorate (Berthollet salt), bleach and many other compounds containing Chlorine atoms.
Bromine and iodine are not used in industry on the same scale as chlorine or fluorine, but the use of these substances is increasing every year. Bromine is used in the production of various sedative medications. Iodine is used in the manufacture of antiseptic drugs. Bromine and Iodine compounds are widely used in the quantitative analysis of substances. Some metals are purified with the help of iodine (this process is called iodine refining), such as titanium, vanadium and others.
Atom, molecule, nuclear properties
Structure of the fluorine atom.
At the center of the atom is a positively charged nucleus. There are 9 negatively charged electrons spinning around.
Electronic formula: 1s2;2s2;2p5
m prot. = 1.00783 (amu)
m neutr.= 1.00866 (a.m.u.)
m proton = m electron
Fluorine isotopes.
Isotope: 18F
a brief description of: Prevalence in nature: 0%
The number of protons in the nucleus is 9. The number of neutrons in the nucleus is 9. The number of nucleons is 18.E bonds = 931.5(9*m pr.+9*m neutron-M(F18)) = 138.24 (MEV)E specific = E bonds/N nucleons = 7.81 (MEV/nucleon)
Alpha decay is impossible Beta minus decay is impossible Positron decay: F(Z=9,M=18)-->O(Z=8,M=18)+e(Z=+1,M=0)+0.28( MeV)Electron capture: F(Z=9,M=18)+e(Z=-1,M=0)-->O(Z=8,M=18)+1.21(MeV)
Isotope: 19F
Brief characteristics: Prevalence in nature: 100%
Fluorine molecule.
Free fluorine consists of diatomic molecules. From the chemical point of view, fluorine can be characterized as a monovalent non-metal, and, moreover, the most active of all non-metals. This is due to a number of reasons, including the ease of decomposition of the F2 molecule into individual atoms - the energy required for this is only 159 kJ/mol (versus 493 kJ/mol for O2 and 242 kJ/mol for C12). Fluorine atoms have significant electron affinity and relatively small sizes. Therefore, their valence bonds with atoms of other elements turn out to be stronger than similar bonds of other metalloids (for example, the H-F bond energy is - 564 kJ/mol versus 460 kJ/mol for the H-O bond and 431 kJ/mol for the H-C1 bond).
F-F communication characterized by a nuclear distance of 1.42 A. For the thermal dissociation of fluorine, the following data were obtained by calculation:
Temperature, °C 300 500 700 900 1100 1300 1500 1700
Degree of dissociation, % 5 10-3 0.3 4.2 22 60 88 97 99
The fluorine atom in its ground state has the structure of the outer electron layer 2s22p5 and is monovalent. The excitation of the trivalent state associated with the transfer of one 2p electron to the 3s level requires a cost of 1225 kJ/mol and is practically not realized. The electron affinity of a neutral fluorine atom is estimated at 339 kJ/mol. The F- ion is characterized by an effective radius of 1.33 A and a hydration energy of 485 kJ/mol. The covalent radius of fluorine is usually taken to be 71 pm (i.e., half the internuclear distance in the F2 molecule).
Chemical properties of fluorine.
Since fluorine derivatives of metalloid elements are usually highly volatile, their formation does not protect the surface of the metalloid from further action of fluorine. Therefore, the interaction is often much more energetic than with many metals. For example, silicon, phosphorus and sulfur ignite in fluorine gas. Amorphous carbon (charcoal) behaves similarly, while graphite reacts only at red heat. Fluorine does not combine directly with nitrogen and oxygen.
Fluorine removes hydrogen from hydrogen compounds of other elements. Most oxides are decomposed by it, displacing oxygen. In particular, water interacts according to the scheme F2 + H2O --> 2 HF + O
Moreover, the displaced oxygen atoms combine not only with each other, but also partially with water and fluorine molecules. Therefore, in addition to oxygen gas, this reaction always produces hydrogen peroxide and fluorine oxide (F2O). The latter is a pale yellow gas similar in smell to ozone.
Fluorine oxide (otherwise known as oxygen fluoride - ОF2) can be obtained by passing fluorine in 0.5 N. NaOH solution. The reaction proceeds according to the equation: 2 F2 + 2 NaOH = 2 NaF + H2O + F2О. The following reactions are also characteristic of fluorine:
H2 + F2 = 2HF (with explosion)
Themes Unified State Exam codifier: Covalent chemical bond, its varieties and mechanisms of formation. Characteristics covalent bond(polarity and binding energy). Ionic bond. Metal connection. Hydrogen bond
Intramolecular chemical bonds
First, let's look at the bonds that arise between particles within molecules. Such connections are called intramolecular.
Chemical bond between atoms chemical elements has an electrostatic nature and is formed due to interaction of external (valence) electrons, in more or less degree held by positively charged nuclei bonded atoms.
The key concept here is ELECTRONEGATIVITY. It is she who determines the type chemical bond between atoms and the properties of this bond.
is the ability of an atom to attract (hold) external(valence) electrons. Electronegativity is determined by the degree of attraction of outer electrons to the nucleus and depends primarily on the radius of the atom and the charge of the nucleus.
Electronegativity is difficult to determine unambiguously. L. Pauling compiled a table of relative electronegativities (based on the bond energies of diatomic molecules). The most electronegative element is fluorine with meaning 4 .
It is important to note that in different sources you can find different scales and tables of electronegativity values. This should not be alarmed, since the formation of a chemical bond plays a role atoms, and it is approximately the same in any system.
If one of the atoms in the A:B chemical bond attracts electrons more strongly, then the electron pair moves towards it. The more electronegativity difference atoms, the more the electron pair shifts.
If the electronegativities of interacting atoms are equal or approximately equal: EO(A)≈EO(B), then the common electron pair does not shift to any of the atoms: A: B. This connection is called covalent nonpolar.
If the electronegativities of the interacting atoms differ, but not greatly (the difference in electronegativity is approximately from 0.4 to 2: 0,4<ΔЭО<2 ), then the electron pair is displaced to one of the atoms. This connection is called covalent polar .
If the electronegativities of interacting atoms differ significantly (the difference in electronegativity is greater than 2: ΔEO>2), then one of the electrons is almost completely transferred to another atom, with the formation ions. This connection is called ionic.
Basic types of chemical bonds − covalent, ionic And metal communications. Let's take a closer look at them.
Covalent chemical bond
Covalent bond – it's a chemical bond , formed due to formation of a common electron pair A:B . Moreover, two atoms overlap atomic orbitals. A covalent bond is formed by the interaction of atoms with a small difference in electronegativity (usually between two non-metals) or atoms of one element.
Basic properties of covalent bonds
- focus,
- saturability,
- polarity,
- polarizability.
These bonding properties influence the chemical and physical properties of substances.
Communication direction characterizes the chemical structure and form of substances. The angles between two bonds are called bond angles. For example, in a water molecule the bond angle H-O-H is 104.45 o, therefore the water molecule is polar, and in a methane molecule the bond angle H-C-H is 108 o 28′.
Saturability is the ability of atoms to form a limited number of covalent chemical bonds. The number of bonds that an atom can form is called.
Polarity bonding occurs due to the uneven distribution of electron density between two atoms with different electronegativity. Covalent bonds are divided into polar and nonpolar.
Polarizability connections are the ability of bond electrons to shift under the influence of an external electric field(in particular, the electric field of another particle). Polarizability depends on electron mobility. The further the electron is from the nucleus, the more mobile it is, and accordingly the molecule is more polarizable.
Covalent nonpolar chemical bond
There are 2 types of covalent bonding – POLAR And NON-POLAR .
Example . Let's consider the structure of the hydrogen molecule H2. Each hydrogen atom in its outer energy level carries 1 unpaired electron. To display an atom, we use the Lewis structure - this is a diagram of the structure of the outer energy level of an atom, when electrons are indicated by dots. Lewis point structure models are quite helpful when working with elements of the second period.
H. + . H = H:H
Thus, a hydrogen molecule has one shared electron pair and one H–H chemical bond. This electron pair does not shift to any of the hydrogen atoms, because Hydrogen atoms have the same electronegativity. This connection is called covalent nonpolar .
Covalent nonpolar (symmetric) bond is a covalent bond formed by atoms with equal electronegativity (usually the same nonmetals) and, therefore, with a uniform distribution of electron density between the nuclei of atoms.
The dipole moment of non-polar bonds is 0.
Examples: H 2 (H-H), O 2 (O=O), S 8.
Covalent polar chemical bond
Covalent polar bond is a covalent bond that occurs between atoms with different electronegativity (usually, various non-metals) and is characterized displacement shared electron pair to a more electronegative atom (polarization).
The electron density is shifted to the more electronegative atom - therefore, a partial negative charge (δ-) appears on it, and a partial positive charge (δ+, delta +) appears on the less electronegative atom.
The greater the difference in electronegativity of atoms, the higher polarity connections and more dipole moment . Additional attractive forces act between neighboring molecules and charges of opposite sign, which increases strength communications.
Bond polarity affects the physical and chemical properties of compounds. The reaction mechanisms and even the reactivity of neighboring bonds depend on the polarity of the bond. The polarity of the connection often determines molecule polarity and thus directly affects such physical properties as boiling point and melting point, solubility in polar solvents.
Examples: HCl, CO 2, NH 3.
Mechanisms of covalent bond formation
Covalent chemical bonds can occur by 2 mechanisms:
1. Exchange mechanism the formation of a covalent chemical bond is when each particle provides one unpaired electron to form a common electron pair:
A . + . B= A:B
2. Covalent bond formation is a mechanism in which one of the particles provides a lone pair of electrons, and the other particle provides a vacant orbital for this electron pair:
A: + B= A:B
In this case, one of the atoms provides a lone pair of electrons ( donor), and the other atom provides a vacant orbital for that pair ( acceptor). As a result of the formation of both bonds, the energy of the electrons decreases, i.e. this is beneficial for the atoms.
A covalent bond formed by a donor-acceptor mechanism is not different in properties from other covalent bonds formed by the exchange mechanism. The formation of a covalent bond by the donor-acceptor mechanism is typical for atoms either with a large number of electrons at the external energy level (electron donors), or, conversely, with a very small number of electrons (electron acceptors). The valence capabilities of atoms are discussed in more detail in the corresponding section.
A covalent bond is formed by a donor-acceptor mechanism:
- in a molecule carbon monoxide CO(the bond in the molecule is triple, 2 bonds are formed by the exchange mechanism, one by the donor-acceptor mechanism): C≡O;
- V ammonium ion NH 4 +, in ions organic amines, for example, in the methylammonium ion CH 3 -NH 2 + ;
- V complex compounds, a chemical bond between the central atom and ligand groups, for example, in sodium tetrahydroxoaluminate Na bond between aluminum and hydroxide ions;
- V nitric acid and its salts- nitrates: HNO 3, NaNO 3, in some other nitrogen compounds;
- in a molecule ozone O3.
Basic characteristics of covalent bonds
Covalent bonds typically form between nonmetal atoms. The main characteristics of a covalent bond are length, energy, multiplicity and directionality.
Multiplicity of chemical bond
Multiplicity of chemical bond - This number of shared electron pairs between two atoms in a compound. The multiplicity of a bond can be determined quite easily from the values of the atoms that form the molecule.
For example , in the hydrogen molecule H 2 the bond multiplicity is 1, because Each hydrogen has only 1 unpaired electron in its outer energy level, hence one shared electron pair is formed.
In the O 2 oxygen molecule, the bond multiplicity is 2, because Each atom at the outer energy level has 2 unpaired electrons: O=O.
In the nitrogen molecule N2, the bond multiplicity is 3, because between each atom there are 3 unpaired electrons at the outer energy level, and the atoms form 3 common electron pairs N≡N.
Covalent bond length
Chemical bond length
is the distance between the centers of the nuclei of the atoms forming the bond. It is determined by experimental physical methods. The bond length can be estimated approximately using the additivity rule, according to which the bond length in the AB molecule is approximately equal to half the sum of the bond lengths in molecules A 2 and B 2: 
The length of a chemical bond can be roughly estimated by atomic radii forming a bond, or by communication multiplicity, if the radii of the atoms are not very different.
As the radii of the atoms forming a bond increase, the bond length will increase.
For example
As the multiplicity of bonds between atoms increases (the atomic radii of which do not differ or differ only slightly), the bond length will decrease.
For example . In the series: C–C, C=C, C≡C, the bond length decreases.
Communication energy
A measure of the strength of a chemical bond is the bond energy. Communication energy determined by the energy required to break a bond and remove the atoms forming that bond to an infinitely large distance from each other.
A covalent bond is very durable. Its energy ranges from several tens to several hundred kJ/mol. The higher the bond energy, the greater the bond strength, and vice versa.
The strength of a chemical bond depends on the bond length, bond polarity, and bond multiplicity. The longer a chemical bond, the easier it is to break, and the lower the bond energy, the lower its strength. The shorter the chemical bond, the stronger it is, and the greater the bond energy.
For example, in the series of compounds HF, HCl, HBr from left to right, the strength of the chemical bond decreases, because The connection length increases.
Ionic chemical bond
Ionic bond is a chemical bond based on electrostatic attraction of ions.
Ions are formed in the process of accepting or donating electrons by atoms. For example, atoms of all metals weakly hold electrons from the outer energy level. Therefore, metal atoms are characterized by restorative properties- ability to donate electrons.
Example. The sodium atom contains 1 electron at energy level 3. By easily giving it up, the sodium atom forms the much more stable Na + ion, with the electron configuration of the noble gas neon Ne. The sodium ion contains 11 protons and only 10 electrons, so the total charge of the ion is -10+11 = +1:
+11Na) 2 ) 8 ) 1 - 1e = +11 Na +) 2 ) 8
Example. A chlorine atom in its outer energy level contains 7 electrons. To acquire the configuration of a stable inert argon atom Ar, chlorine needs to gain 1 electron. After adding an electron, a stable chlorine ion is formed, consisting of electrons. The total charge of the ion is -1:
+17Cl) 2 ) 8 ) 7 + 1e = +17 Cl — ) 2 ) 8 ) 8
Note:
- The properties of ions are different from the properties of atoms!
- Stable ions can form not only atoms, but also groups of atoms. For example: ammonium ion NH 4 +, sulfate ion SO 4 2-, etc. Chemical bonds formed by such ions are also considered ionic;
- Ionic bonds are usually formed between each other metals And nonmetals(non-metal groups);
The resulting ions are attracted due to electrical attraction: Na + Cl -, Na 2 + SO 4 2-.
Let us visually summarize difference between covalent and ionic bond types:
Metal chemical bond
Metal connection is a connection that is formed relatively free electrons between metal ions, forming a crystal lattice.
Metal atoms are usually located on the outer energy level one to three electrons. The radii of metal atoms, as a rule, are large - therefore, metal atoms, unlike non-metals, give up their outer electrons quite easily, i.e. are strong reducing agents
Intermolecular interactions
Separately, it is worth considering the interactions that arise between individual molecules in a substance - intermolecular interactions . Intermolecular interactions are a type of interaction between neutral atoms in which no new covalent bonds appear. The forces of interaction between molecules were discovered by Van der Waals in 1869, and named after him Van dar Waals forces. Van der Waals forces are divided into orientation, induction And dispersive . The energy of intermolecular interactions is much less than the energy of chemical bonds.
Orientation forces of attraction occur between polar molecules (dipole-dipole interaction). These forces occur between polar molecules. Inductive interactions is the interaction between a polar molecule and a non-polar one. A nonpolar molecule is polarized due to the action of a polar one, which generates additional electrostatic attraction.
A special type of intermolecular interaction is hydrogen bonds. - these are intermolecular (or intramolecular) chemical bonds that arise between molecules that have highly polar covalent bonds - H-F, H-O or H-N. If there are such bonds in a molecule, then between the molecules there will be additional attractive forces .
Education mechanism hydrogen bonding is partly electrostatic and partly donor-acceptor. In this case, the electron pair donor is an atom of a strongly electronegative element (F, O, N), and the acceptor is the hydrogen atoms connected to these atoms. Hydrogen bonds are characterized by focus in space and saturation
Hydrogen bonds can be indicated by dots: H ··· O. The greater the electronegativity of the atom connected to hydrogen, and the smaller its size, the stronger the hydrogen bond. It is typical primarily for connections fluorine with hydrogen , as well as to oxygen and hydrogen , less nitrogen with hydrogen .
Hydrogen bonds occur between the following substances:
— hydrogen fluoride HF(gas, solution of hydrogen fluoride in water - hydrofluoric acid), water H 2 O (steam, ice, liquid water):
— solution of ammonia and organic amines- between ammonia and water molecules;
— organic compounds in which O-H or N-H bonds: alcohols, carboxylic acids, amines, amino acids, phenols, aniline and its derivatives, proteins, solutions of carbohydrates - monosaccharides and disaccharides.
Hydrogen bonding affects the physical and chemical properties of substances. Thus, additional attraction between molecules makes it difficult for substances to boil. Substances with hydrogen bonds exhibit an abnormal increase in boiling point.
For example As a rule, with increasing molecular weight, an increase in the boiling point of substances is observed. However, in a number of substances H 2 O-H 2 S-H 2 Se-H 2 Te we do not observe a linear change in boiling points.
Namely, at water boiling point is abnormally high - no less than -61 o C, as the straight line shows us, but much more, +100 o C. This anomaly is explained by the presence of hydrogen bonds between water molecules. Therefore, under normal conditions (0-20 o C) water is liquid by phase state.
(first electron)
(according to Pauling)
| F | 9 |
| 18,9984 | |
| 2s 2 2p 5 | |
| Fluorine | |
Chemical properties
The most active non-metal, it interacts violently with almost all substances (rare exceptions are fluoroplastics), and with most of them - with combustion and explosion. Contact of fluorine with hydrogen leads to ignition and explosion even at very low temperatures (down to −252°C). Even water and platinum:uranium for the nuclear industry burn in a fluorine atmosphere.
chlorine trifluoride ClF 3 - a fluorinating agent and a powerful oxidizer of rocket fuel
sulfur hexafluoride SF 6 - gaseous insulator in the electrical industry
metal fluorides (such as W and V), which have some beneficial properties
freons are good refrigerants
teflon - chemically inert polymers
sodium hexafluoroaluminate - for subsequent production of aluminum by electrolysis
various fluorine compounds
Rocketry
Fluorine compounds are widely used in rocket technology as an oxidizer for rocket fuel.Application in medicine
Fluorine compounds are widely used in medicine as blood substitutes.
Biological and physiological role
Fluorine is a vital element for the body. In the human body, fluorine is mainly found in tooth enamel in the composition of fluorapatite - Ca 5 F (PO 4) 3. With insufficient (less than 0.5 mg/liter of drinking water) or excessive (more than 1 mg/liter) consumption of fluoride, the body can develop dental diseases: caries and fluorosis (mottling of enamel) and osteosarcoma, respectively.
To prevent caries, it is recommended to use toothpastes with fluoride additives or drink fluoridated water (up to a concentration of 1 mg/l), or use local applications of a 1-2% solution of sodium fluoride or stannous fluoride. Such actions can reduce the likelihood of tooth decay by 30-50%.
The maximum permissible concentration of bound fluorine in the air of industrial premises is 0.0005 mg/liter.
Additional Information
Fluorine, Fluorum, F(9)
Fluorine (Fluorine, French and German Fluor) was obtained in a free state in 1886, but its compounds have been known for a long time and were widely used in metallurgy and glass production. The first mention of fluorite (CaP) under the name fluorspar (Fliisspat) dates back to the 16th century. One of the works attributed to the legendary Vasily Valentin mentions stones painted in various colors - flux (Fliisse from the Latin fluere - to flow, pour), which were used as fluxes in the smelting of metals. Agricola and Libavius write about this. The latter introduces special names for this flux - fluorspar (Flusspat) and mineral fluors. Many authors of chemical and technical works of the 17th and 18th centuries. describe different types of fluorspar. In Russia these stones were called fin, spalt, spat; Lomonosov classified these stones as selenites and called them spar or flux (crystal flux). Russian craftsmen, as well as collectors of mineral collections (for example, in the 18th century, Prince P.F. Golitsyn) knew that some types of spar when heated (for example, in hot water) glow in the dark. However, Leibniz, in his history of phosphorus (1710), mentions thermophosphorus (Thermophosphorus) in this regard.
Apparently, chemists and artisan chemists became acquainted with hydrofluoric acid no later than the 17th century. In 1670, the Nuremberg artisan Schwanhard used fluorspar mixed with sulfuric acid to etch patterns on glass goblets. However, at that time the nature of fluorspar and hydrofluoric acid was completely unknown. It was believed, for example, that silicic acid had a pickling effect in the Schwanhard process. This erroneous opinion was eliminated by Scheele, who proved that when fluorspar reacts with sulfuric acid, silicic acid is obtained as a result of the corrosion of a glass retort by the resulting hydrofluoric acid. In addition, Scheele established (1771) that fluorspar is a combination of calcareous earth with a special acid, which was called “Swedish acid”.
Lavoisier recognized the hydrofluoric acid radical as a simple body and included it in his table of simple bodies. Hydrofluoric acid was obtained in more or less pure form in 1809. Gay-Lussac and Thénard by distilling fluorspar with sulfuric acid in a lead or silver retort. During this operation, both researchers were poisoned. The true nature of hydrofluoric acid was established in 1810 by Ampere. He rejected Lavoisier's opinion that hydrofluoric acid should contain oxygen, and proved the analogy of this acid with hydrochloric acid. Ampere reported his findings to Davy, who had recently established the elemental nature of chlorine. Davy completely agreed with Ampere's arguments and spent a lot of effort on obtaining free fluorine by electrolysis of hydrofluoric acid and other ways. Taking into account the strong corrosive effect of hydrofluoric acid on glass, as well as on plant and animal tissues, Ampere proposed calling the element contained in it fluorine (Greek - destruction, death, pestilence, plague, etc.). However, Davy did not accept this name and proposed another - Fluorine, by analogy with the then name of chlorine - Chlorine, both names are still used in English. The name given by Ampere has been preserved in Russian.
Numerous attempts to isolate free fluorine in the 19th century. did not lead to successful results. Only in 1886 did Moissan manage to do this and obtain free fluorine in the form of a yellow-green gas. Since fluorine is an unusually aggressive gas, Moissan had to overcome many difficulties before he found a material suitable for equipment in experiments with fluorine. The U-tube for electrolysis of hydrofluoric acid at 55°C (cooled with liquid methyl chloride) was made of platinum with fluorspar plugs. After the chemical and physical properties of free fluorine were studied, it found wide application. Now fluorine is one of the most important components in the synthesis of a wide range of organofluorine substances. In Russian literature of the early 19th century. fluorine was called differently: hydrofluoric acid base, fluorin (Dvigubsky, 1824), fluoricity (Iovsky), fluor (Shcheglov, 1830), fluor, fluorine, fluoride. Hess introduced the name fluorine in 1831.
The work contains tasks on chemical bonds.
Pugacheva Elena Vladimirovna
Description of the development
6. Covalent nonpolar bond is characteristic of
1) Cl 2 2) SO3 3) CO 4) SiO 2
1) NH 3 2) Cu 3) H 2 S 4) I 2
3) ionic 4) metal
15. Three common electron pairs form a covalent bond in a molecule
16. Hydrogen bonds form between molecules
1) HI 2) HCl 3) HF 4) HBr
1) water and diamond 2) hydrogen and chlorine 3) copper and nitrogen 4) bromine and methane
19. Hydrogen bond not typical for substance
1) fluorine 2) chlorine 3) bromine 4) iodine
1)СF 4 2)CCl 4 3)CBr 4 4)CI 4
1) 1 2) 2 3) 3 4) 4
1) 1 2) 2 3) 3 4) 4
32. Atoms of chemical elements of the second period of the periodic table D.I. Mendeleev form compounds with ionic chemical bonds of the composition 1) LiF 2) CO 2 3) Al 2 O 3 4) BaS
1) ionic 2) metal
43. An ionic bond is formed by 1) H and S 2) P and C1 3) Cs and Br 4) Si and F
when interacting
1) ionic 2) metal
1) ionic 2) metal
NAME OF SUBSTANCE TYPE OF COMMUNICATION
1) zinc A) ionic
2) nitrogen B) metal
62. Match
COMMUNICATION TYPE CONNECTION
1) ionic A) H 2
2) metal B) Va
3) covalent polar B) HF
66. The strongest chemical bond occurs in the molecule 1) F 2 2) Cl 2 3) O 2 4) N 2
67. Bond strength increases in the series 1) Cl 2 -O 2 -N 2 2) O 2 - N 2- Cl 2 3) O 2 - Cl 2 -N 2 4) Cl 2 -N 2 -O 2
68. Indicate a series characterized by an increase in the length of a chemical bond
1) O 2 , N 2 , F 2 , Cl 2 2) N 2 , O 2 , F 2 , Cl 2 3) F 2 , N 2 , O 2 , Cl 2 4) N 2 , O 2 , Cl 2 , F 2
Let's look at task No. 3 from the Unified State Exam options for 2016.
Tasks with solutions.
Task No. 1.
Compounds with a covalent nonpolar bond are located in the series:
1. O2, Cl2, H2
2. HCl, N2, F2
3. O3, P4, H2O
4.NH3, S8, NaF
Explanation: we need to find a series in which there will only be simple substances, since a covalent nonpolar bond is formed only between atoms of the same element. The correct answer is 1.
Task No. 2.
Substances with covalent polar bonds are listed in the following series:
1. CaF2, Na2S, N2
2. P4, FeCl2, NH3
3. SiF4, HF, H2S
4. NaCl, Li2O, SO2
Explanation: here you need to find a series in which only complex substances and, moreover, all non-metals. The correct answer is 3.
Task No. 3.
Hydrogen bonding is characteristic of
1. Alkanov 2. Arenov 3. Alcohols 4. Alkinov
Explanation: A hydrogen bond is formed between a hydrogen ion and an electronegative ion. Among those listed, only alcohols have such a set.
The correct answer is 3.
Task No. 4.
Chemical bond between water molecules
1. Hydrogen
2. Ionic
3. Covalent polar
4. Covalent nonpolar
Explanation: A polar covalent bond is formed between the O and H atoms in water, since these are two non-metals, but there is a hydrogen bond between water molecules. The correct answer is 1.
Task No. 5.
Each of the two substances has only covalent bonds:
1. CaO and C3H6
2. NaNO3 and CO
3. N2 and K2S
4. CH4 and SiO2
Explanation: connections must consist only of non-metals, that is the correct answer is 4.
Task No. 6.
A substance with a polar covalent bond is
1. O3 2. NaBr 3. NH3 4. MgCl2
Explanation: A polar covalent bond is formed between atoms of different nonmetals. The correct answer is 3.
Task No. 7.
A nonpolar covalent bond is characteristic of each of two substances:
1. Water and diamond
2. Hydrogen and chlorine
3. Copper and nitrogen
4. Bromine and methane
Explanation: a non-polar covalent bond is characteristic of the connection of atoms of the same non-metal element. The correct answer is 2.
Task No. 8.
What chemical bond is formed between atoms of elements with atomic numbers 9 and 19?
1. Ionic
2. Metal
3. Covalent polar
4. Covalent nonpolar
Explanation: these are the elements - fluorine and potassium, that is, a non-metal and a metal, respectively, only an ionic bond can form between such elements. The correct answer is 1.
Task No. 9.
A substance with an ionic type of bond corresponds to the formula
1. NH3 2. HBr 3. CCl4 4. KCl
Explanation: an ionic bond is formed between a metal atom and a non-metal atom, that is the correct answer is 4.
Task No. 10.
Hydrogen chloride and
1. Ammonia
2. Bromine
3. Sodium chloride
4. Magnesium oxide
Explanation: Hydrogen chloride has a covalent polar bond, that is, we need to find a substance consisting of two different non-metals - this is ammonia.
The correct answer is 1.
Tasks for independent solution.
1. Hydrogen bonds form between molecules
1. Hydrofluoric acid
2. Methane chloride
3. Dimethyl ether
4. Ethylene
2. A compound with a covalent bond corresponds to the formula
1. Na2O 2. MgCl2 3. CaBr2 4. HF
3. A substance with a covalent nonpolar bond has the formula
1. H2O 2. Br2 3. CH4 4. N2O5
4. A substance with an ionic bond is
1. CaF2 2. Cl2 3. NH3 4. SO2
5. Hydrogen bonds form between molecules
1. Methanol
3. Acetylene
4. Methyl formate
6. A covalent nonpolar bond is characteristic of each of two substances:
1. Nitrogen and ozone
2. Water and ammonia
3. Copper and nitrogen
4. Bromine and methane
7. A covalent polar bond is characteristic of a substance
1. KI 2. CaO 3. Na2S 4. CH4
8. Covalent nonpolar bond is characteristic of
1. I2 2. NO 3. CO 4. SiO2
9. A substance with a covalent polar bond is
1. Cl2 2. NaBr 3. H2S 4. MgCl2
10. A covalent nonpolar bond is characteristic of each of two substances:
1. Hydrogen and chlorine
2. Water and diamond
3. Copper and nitrogen
4. Bromine and methane
This note uses tasks from the 2016 Unified State Exam collection edited by A.A. Kaverina.
A4 Chemical bond.
Chemical bond: covalent (polar and non-polar), ionic, metallic, hydrogen. Methods for forming covalent bonds. Characteristics of a covalent bond: length and bond energy. Formation of ionic bond.
Option 1 – 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61,65
Option 2 – 2,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,66
Option 3 – 3,7,11,15,19,23,27,31,35,39,43,47,51,55,59,63,67
Option 4 – 4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68
1. In ammonia and barium chloride, the chemical bond is respectively
1) ionic and covalent polar
2) covalent polar and ionic
3) covalent nonpolar and metallic
4) covalent nonpolar and ionic
2. Substances with only ionic bonds are listed in the following series:
1) F 2, CCl 4, KCl 2) NaBr, Na 2 O, KI 3) SO 2 .P 4 .CaF 2 4) H 2 S, Br 2, K 2 S
3. A compound with an ionic bond is formed by interaction
1) CH 4 and O 2 2) SO 3 and H 2 O 3) C 2 H 6 and HNO 3 4) NH 3 and HCI
4. In which series do all substances have a polar covalent bond?
1) HCl,NaCl,Cl 2 2) O 2,H 2 O,CO 2 3) H 2 O,NH 3,CH 4 4) NaBr,HBr,CO
5. In which series are the formulas of substances with only a polar covalent bond written?
1) Cl 2, NO 2, HCl 2) HBr,NO,Br 2 3) H 2 S,H 2 O,Se 4) HI,H 2 O,PH 3
6. Covalent nonpolar bond is characteristic of
1) Cl 2 2) SO3 3) CO 4) SiO 2
7. A substance with a polar covalent bond is
1) C1 2 2) NaBr 3) H 2 S 4) MgCl 2
8. A substance with a covalent bond is
1) CaCl 2 2) MgS 3) H 2 S 4) NaBr
9. A substance with a covalent nonpolar bond has the formula
1) NH 3 2) Cu 3) H 2 S 4) I 2
10. Substances with non-polar covalent bonds are
11. A chemical bond is formed between atoms with the same electronegativity
1) ionic 2) covalent polar 3) covalent nonpolar 4) hydrogen
12. Covalent polar bonds are characteristic of
1) KCl 2) HBr 3) P 4 4) CaCl 2
13. A chemical element in the atom of which the electrons are distributed among the layers as follows: 2, 8, 8, 2 forms a chemical bond with hydrogen
1) covalent polar 2) covalent nonpolar
3) ionic 4) metal
14. In the molecule of which substance does the bond between carbon atoms have the longest length?
1) acetylene 2) ethane 3) ethene 4) benzene
15. Three common electron pairs form a covalent bond in a molecule
1) nitrogen 2) hydrogen sulfide 3) methane 4) chlorine
16. Hydrogen bonds form between molecules
1) dimethyl ether 2) methanol 3) ethylene 4) ethyl acetate
17. Bond polarity is most pronounced in the molecule
1) HI 2) HCl 3) HF 4) HBr
18. Substances with non-polar covalent bonds are
1) water and diamond 2) hydrogen and chlorine 3) copper and nitrogen 4) bromine and methane
19. Hydrogen bond not typical for substance
1) H 2 O 2) CH 4 3) NH 3 4) CH3OH
20. A covalent polar bond is characteristic of each of the two substances whose formulas are
1) KI and H 2 O 2) CO 2 and K 2 O 3) H 2 S and Na 2 S 4) CS 2 and PC1 5
21. The weakest chemical bond in a molecule
22. Which substance has the longest chemical bond in its molecule?
1) fluorine 2) chlorine 3) bromine 4) iodine
23. Each of the substances indicated in the series has covalent bonds:
1) C 4 H 10, NO 2, NaCl 2) CO, CuO, CH 3 Cl 3) BaS, C 6 H 6, H 2 4) C 6 H 5 NO 2, F 2, CCl 4
24. Each of the substances indicated in the series has a covalent bond:
1) CaO, C 3 H 6, S 8 2) Fe, NaNO 3, CO 3) N 2, CuCO 3, K 2 S 4) C 6 H 5 N0 2, SO 2, CHC1 3
25. Each of the substances indicated in the series has a covalent bond:
1) C 3 H 4, NO, Na 2 O 2) CO, CH 3 C1, PBr 3 3) P 2 Oz, NaHSO 4, Cu 4) C 6 H 5 NO 2, NaF, CCl 4
26. Each of the substances indicated in the series has covalent bonds:
1) C 3 H a, NO 2, NaF 2) KCl, CH 3 Cl, C 6 H 12 0 6 3) P 2 O 5, NaHSO 4, Ba 4) C 2 H 5 NH 2, P 4, CH 3 OH
27. Bond polarity is most pronounced in molecules
1) hydrogen sulfide 2) chlorine 3) phosphine 4) hydrogen chloride
28. In the molecule of which substance are the chemical bonds the strongest?
1)СF 4 2)CCl 4 3)CBr 4 4)CI 4
29. Among the substances NH 4 Cl, CsCl, NaNO 3, PH 3, HNO 3 - the number of compounds with ionic bonds is equal
1) 1 2) 2 3) 3 4) 4
30. Among the substances (NH 4) 2 SO 4, Na 2 SO 4, CaI 2, I 2, CO 2 - the number of compounds with a covalent bond is equal
1) 1 2) 2 3) 3 4) 4
31. In substances formed by joining identical atoms, a chemical bond
1) ionic 2) covalent polar 3) hydrogen 4) covalent nonpolar
32. Atoms of chemical elements of the second period of the periodic table D.I. Mendeleev form compounds with ionic chemical bonds of the composition 1) LiF 2) CO 2 3) Al 2 O 3 4) BaS
33. Compounds with covalent polar and covalent nonpolar bonds are, respectively, 1) water and hydrogen sulfide 2) potassium bromide and nitrogen 3) ammonia and hydrogen 4) oxygen and methane
34. Covalent nonpolar bonds are characteristic of 1) water 2) ammonia 3) nitrogen 4) methane
35. Chemical bond in a hydrogen fluoride molecule
1) covalent polar 3) ionic
2) covalent nonpolar 4) hydrogen
36. Select a pair of substances in which all bonds are covalent:
1) NaCl, HCl 2) CO 2, BaO 3) CH 3 Cl, CH 3 Na 4) SO 2, NO 2
37. In potassium iodide the chemical bond
1) covalent nonpolar 3) metallic
2) covalent polar 4) ionic
38. In carbon disulfide CS 2 chemical bond
1) ionic 2) metal
3) covalent polar 4) covalent nonpolar
39. A covalent nonpolar bond is realized in a compound
1) CrO 3 2) P 2 O 5 3) SO 2 4) F 2
40. A substance with a covalent polar bond has the formula 1) KCl 2) HBr 3) P 4 4) CaCl 2
41. Compound with an ionic chemical bond
1) phosphorus chloride 2) potassium bromide 3) nitrogen oxide (II) 4) barium
42. In ammonia and barium chloride, the chemical bond is respectively
1) ionic and covalent polar 2) covalent polar and ionic
3) covalent non-polar and metallic 4) covalent non-polar and ionic
43. An ionic bond is formed by 1) H and S 2) P and C1 3) Cs and Br 4) Si and F
44. What type of bond is in the H2 molecule?
1) Ionic 2) Hydrogen 3) Covalent nonpolar 4) Donor-acceptor
45. Substances with a covalent polar bond are
1) sulfur oxide (IV) 2) oxygen 3) calcium hydride 4) diamond
46. There is a chemical bond in the fluorine molecule
1) covalent polar 2) ionic 3) covalent nonpolar 4) hydrogen
47. Which series lists substances with only covalent polar bonds:
1) CH 4 H 2 Cl 2 2) NH 3 HBr CO 2 3) PCl 3 KCl CCl 4 4) H 2 S SO 2 LiF
48. In which series do all substances have a polar covalent bond?
1) HCl, NaCl, Cl 2 2) O 2 H 2 O, CO 2 3) H 2 O, NH 3, CH 4 4) KBr, HBr, CO
49. Which series lists substances with only ionic bonds:
1) F 2 O LiF SF 4 2) PCl 3 NaCl CO 2 3) KF Li 2 O BaCl 2 4) CaF 2 CH 4 CCl 4
50. A compound with an ionic bond is formed when interacting
1) CH 4 and O 2 2) NH 3 and HCl 3) C 2 H 6 and HNO 3 4) SO 3 and H 2 O
51. A hydrogen bond is formed between the molecules of 1) ethane 2) benzene 3) hydrogen 4) ethanol
52. Which substance has hydrogen bonds? 1) Hydrogen sulfide 2) Ice 3) Hydrogen bromide 4) Benzene
53. The connection formed between elements with serial numbers 15 and 53
1) ionic 2) metal
3) covalent non-polar 4) covalent polar
54. The connection formed between elements with serial numbers 16 and 20
1) ionic 2) metal
3) covalent polar 4) hydrogen
55. A bond arises between atoms of elements with serial numbers 11 and 17
1) metallic 2) ionic 3) covalent 4) donor-acceptor
56. Hydrogen bonds form between molecules
1) hydrogen 2) formaldehyde 3) acetic acid 4) hydrogen sulfide
57. In which series are the formulas of substances with only a polar covalent bond written?
1) Cl 2, NH 3, HCl 2) HBr, NO, Br 2 3) H 2 S, H 2 O, S 8 4) HI, H 2 O, PH 3
58.Which substance contains both ionic and covalent chemical bonds?
1) Sodium chloride 2) Hydrogen chloride 3) Sodium sulfate 4) Phosphoric acid
59. A chemical bond in a molecule has a more pronounced ionic character
1) lithium bromide 2) copper chloride 3) calcium carbide 4) potassium fluoride
60. In which substance are all chemical bonds covalent nonpolar?
1) Diamond 2) Carbon monoxide (IV) 3) Gold 4) Methane
61. Establish a correspondence between a substance and the type of connection of atoms in this substance.
NAME OF SUBSTANCE TYPE OF COMMUNICATION
1) zinc A) ionic
2) nitrogen B) metal
3) ammonia B) covalent polar
4) calcium chloride D) covalent nonpolar
62. Match
COMMUNICATION TYPE CONNECTION
1) ionic A) H 2
2) metal B) Va
3) covalent polar B) HF
4) covalent nonpolar D) BaF 2
63. In which compound is a covalent bond between atoms formed by a donor-acceptor mechanism? 1) KCl 2) CCl 4 3) NH 4 Cl 4) CaCl 2
64. Indicate the molecule in which the binding energy is the highest: 1) N≡N 2) H-H 3) O=O 4) H-F
65. Indicate the molecule in which the chemical bond is the strongest: 1) HF 2) HCl 3) HBr 4) HI
