Types of chemical bonds assignments. Types of chemical bond
Atoms can combine with each other to form both simple and complex substances. In this case, various types chemical bonds: ionic, covalent (non-polar and polar), metallic.
One of the most essential properties of atoms of elements, which determines what kind of bond is formed between them, is electronegativity, i.e. the ability of atoms in a compound to attract electrons.
The more an atom attracts electrons to itself, the higher its electronegativity. Electronegativity depends on the size of the atom and the charge of its nucleus. The sizes of atoms of elements of the same period decrease with increasing nuclear charge. This happens because the charge of the atomic nucleus increases from element to element, but the number of electron layers remains the same. In this case, the atom becomes more compact, the size of the atom decreases towards the end of the period, and the force of attraction of electrons by the nucleus increases. Therefore, the electronegativity of elements increases in a period.
For elements of the main subgroups, as the nuclear charges increase, the number of electronic layers also increases, and therefore the size of the atoms increases. The attraction of outer electrons decreases. Therefore, the electronegativity of elements in a group decreases.
Non-metal elements have the greatest electronegativity: fluorine, oxygen, nitrogen and others. Metal elements have lower electronegativity. The lowest electronegativity is found in elements such as potassium, sodium, and calcium. In descending order of electronegativity, elements can be arranged in a row:
F, O, N, Cl, Br, S, I, C, Se, P, H, B, Si, Cu. Fe, Zn. Al, Mg, Li, Ca, Na, K
The electronegativity of fluorine is conventionally taken to be 4.0; The electronegativity of potassium is 0.8.
The type of chemical bond depends on how large the difference in electronegativity values of the connecting atoms of elements is. The more the atoms of the elements forming the bond differ in electronegativity, the more polar the chemical bond.
1. An ionic bond is formed by the interaction of atoms that differ sharply from each other in electronegativity. For example, the typical metals lithium (Li), sodium (Na), potassium (K), calcium (Ca), strontium (Sr), barium (Ba) form ionic bonds with typical nonmetals. This produces a metal ion with a positive charge and a non-metal ion with a negative charge.
2. Covalent is a bond between non-metal atoms, as a result of which common electron pairs are formed.
There are non-polar and polar covalent bonds.
When atoms with the same electronegativity interact, molecules with a covalent nonpolar bond are formed. Such a connection exists in the molecules of simple substances: hydrogen, oxygen, nitrogen, chlorine, etc. Chemical bonds in these are formed through shared electron pairs, i.e. when the corresponding electron clouds overlap, due to electron-nuclear interaction when atoms approach each other.
When atoms whose electronegativity values differ, but not sharply, interact, the common electron pair shifts to a more electronegative atom and a polar covalent bond is formed. In this case, partial charges are formed. This is the most common type of chemical bond, found in both inorganic and organic compounds.
3. Metallic is a bond that is formed as a result of the interaction of relatively free electrons with metal ions. This type of bond is characteristic of simple substances - metals and their alloys. The essence of the process of metal bond formation 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. A metallic bond arises between them.
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 a chemical bond is closer in nature, it is classified as either an ionic or a covalent polar bond.
Basic types of chemical bond.
You know that atoms can combine with each other to form both simple and complex substances. In this case, various types of chemical bonds are formed: ionic, covalent (non-polar and polar), metallic and hydrogen. One of the most essential properties of atoms of elements, which determine what kind of bond is formed between them - ionic or covalent - This is electronegativity, i.e. the ability of atoms in a compound to attract electrons.
A conditional quantitative assessment of electronegativity is given by the relative electronegativity scale.
In periods, there is a general tendency for the electronegativity of elements to increase, and in groups - for their decrease. Elements are arranged in a row according to their electronegativity, on the basis of which the electronegativity of elements located in different periods can be compared.
The type of chemical bond depends on how large the difference in electronegativity values of the connecting atoms of elements is. The more the atoms of the elements forming the bond differ in electronegativity, the more polar the chemical bond. 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 a chemical bond is closer in nature, it is classified 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, the typical metals lithium (Li), sodium (Na), potassium (K), calcium (Ca), strontium (Sr), barium (Ba) form ionic bonds with typical non-metals, mainly halogens.
In addition to alkali metal halides, ionic bonds also form 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 remaining bonds are polar covalent).
Covalent nonpolar bond.
When atoms with the same electronegativity interact, molecules with a covalent nonpolar bond are formed. 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 shared electron pairs, i.e. when the corresponding electron clouds overlap, due to the electron-nuclear interaction, which occurs when atoms approach each other.
Composing electronic formulas substances, it should be remembered that each common electron pair is a conventional image of increased electron density resulting from the overlap of the corresponding electron clouds.
Covalent polar bond.
When atoms interact, the electronegativity values of which differ, but not sharply, the common electron pair shifts to a more electronegative atom. This is the most common type of chemical bond, found in both inorganic and organic compounds.
Covalent bonds also fully include those bonds that are formed by a 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 characteristic of simple substances - metals.
The essence of the process of metal bond formation 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. A metallic bond arises between them, i.e. Electrons, as it were, cement the positive ions of the crystal lattice of metals.
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 does hydrogen form such a specific chemical bond?
This is explained by the fact that the atomic radius of hydrogen is very small. In addition, when displacing or completely donating its only electron, 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 goes into the composition of other molecules (HF, H 2 O, NH 3) .
Let's look at some examples. Usually we depict the composition of water 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 = 2,3,4, etc. This is explained by the fact that individual water molecules are connected to each other through hydrogen bonds.
Hydrogen bonds are usually denoted by dots. It is much weaker than ionic or covalent bonds, but stronger than ordinary intermolecular interactions.
The presence of hydrogen bonds explains the increase in water volume 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 arose: why are the boiling points of alcohols much higher than the corresponding hydrocarbons? This is explained by the fact that hydrogen bonds also form between alcohol molecules.
An increase in the boiling point of alcohols also occurs due to the enlargement of their molecules.
Hydrogen bonding 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.
MUNICIPAL EDUCATIONAL INSTITUTION
"SECONDARY SCHOOL No. 63, BRYANSK"
HANDOUT ON THE TOPIC
"CHEMICAL BOND"
chemistry
8th grade
Chemistry teacher
MBOU Secondary School No. 63, Bryansk
Gaidukova Alexandra Pavlovna
Chemical bond. Basic types of chemical bonds.
Remember!- What is electronegativity? How does the electronegativity of elements change within a period? How does the electronegativity of elements change within the main subgroups?
Task 2. Determine which of the two elements has less ability to attract electrons from other atoms. Please mark your answer with a tick. a) NaP; b) O and Se; c) Cl and Rb; d) Ca and Ba; e) Сs and Al
Task 3. Specify a pair of elements that have the same EO value: Li – K; F – Br; Cl – Cl; Na–Cl Explore! Chemical bond– such interaction of atoms of chemical elements that leads to the formation of stable structures (molecules, ions, crystals).
Types of Chemical Bonds
- Covalent bond. Occurs between atoms of non-metal elements. There are two types of covalent bonds: a) covalent nonpolar bonds arise between atoms of non-metal elements with the same value EO; b) covalent polar bonds arise between atoms of non-metal elements with different meaning EO. Ionic bond. Occurs between atoms of a metal element and a non-metal element, the EO values of which differ sharply. Metal connection. Occurs between atoms of a given metal. Hydrogen bond. Occurs between hydrogen atom one molecule
And more electronegative element another molecule
.
Task 5. Complete Table 1 and make a conclusion about the type of chemical bond in each compound.*cm. table 1 on the adjacent side
Task 6. I option). Determine the type of chemical bond in compounds whose formulas are given: SO 3 _________________________________________
ClF 3 ________________________________________
Br 2 ________________________________________
(H 2 O) 3 ________________________________________________
CaCl 2 _______________________________________________
Cu__________________________________________
Task 7. (Complete this task if you are on II option). Determine the type of chemical bond in the compounds whose formulas are given: N 2 _________________________________________
CO 2 ________________________________________
KI__________________________________________
(NH 3) 2 ________________________________________________
HBr__________________________________________
Mg__________________________________________
Teacher rating
Covalent chemical bond
Remember!- What is a chemical bond? List all types of chemical bonds. What chemical bond is called covalent? Name two types of covalent chemical bonds. Define them.
Task 2. From the formulas of substances below, write down the formulas of compounds with a covalent nonpolar bond: I 2 ; HCl, O 2, NH 3, H 2 O, N 2, Cl 2, Ag.
____________________________________________________________________ Explore! A covalent chemical bond is a bond that arises between atoms of non-metal elements due to the formation of one or more shared electron pairs. Electron pairs between atoms are formed by combining the unpaired electrons of each atom. The number of unpaired electrons in a nonmetal atom ( VA – VIIA group, IVA – in excited state) can be calculated using the formula:
Number of unpaired e = 8 – N G ,
where N g is the number of the group in which the element is located
Do it! Task 3. Fill the table:Non-metal element
Keep exploring!
Mechanism of formation of a covalent nonpolar bond
Let us consider the mechanism of formation of a covalent nonpolar bond using the example of a hydrogen molecule H2. (Explain why there is a covalent nonpolar bond in the hydrogen molecule?). The H2 molecule contains two hydrogen atoms: H and H. Draw electron graphic formulas for the structure of each atom:
N N
As can be seen from the electron-graphical formulas you constructed, the number of unpaired electrons in each hydrogen atom is ________. Connect the unpaired electrons of each atom with a wavy line. You have obtained a schematic representation of the formation of a covalent nonpolar bond in a hydrogen molecule.
Summarize! Each hydrogen atom has ______ unpaired electron located at _____ energy level. This energy level can only hold two electrons. Therefore, a hydrogen atom needs another ______ electron to complete its energy level. During the formation of a chemical bond, a common electron pair is formed between hydrogen atoms, which belongs equally to each hydrogen atom. As a result, each atom has ______ electrons. Since both hydrogen atoms have the same EO value, the shared electron pair does not shift towards either atom. Therefore, this type of bond is called covalent non-polar communication Electronic circuit the formation of a covalent nonpolar bond in a hydrogen molecule looks like this:
N . + . N N : N.If you replace a common electron pair with a bar, you will get the structural formula of the molecule: H – H. If there are several common electron pairs, each pair is replaced with a bar.
Do it!
Task 4. Draw the mechanism of formation of covalent nonpolar bonds in molecules Cl 2 , O 2 using electron-graphical, electronic and structural formulas. Next to the diagrams, indicate: a) the number of unpaired electrons of each atom; b) the number of electrons in the outer level of each atom; c) the number of common electron pairs in each molecule.
Complete the task on blank page 4
Keep exploring!
Mechanism of formation of a polar covalent bond
Let us consider the mechanism of formation of a covalent nonpolar bond using the example of a hydrogen chloride molecule HCl (Explain why there is a covalent polar bond in the hydrogen chloride molecule?). The HCl molecule contains two atoms: _____ and ______. Draw electron graphic formulas for the structure of each atom:
As can be seen from the formulas you constructed, the hydrogen atom has _____unpaired electron, and the chlorine atom has _____unpaired electron. Connect the unpaired electrons of each atom with a wavy line. You have obtained a schematic representation of the formation of a covalent field bond in a hydrogen chloride molecule.
Summarize! The hydrogen atom has______ an unpaired electron located at the_____ energy level, and the chlorine atom has______an unpaired electron located at the _____ energy level. Therefore, a hydrogen atom and a chlorine atom need another ______ electron to complete the energy level. During the formation of a chemical bond, a common electron pair is formed between hydrogen atoms, which belongs to both the hydrogen atom and the chlorine atom. As a result, each atom has a complete electron shell. The shared electron pair in the case of a polar covalent bond is shifted towards the more electronegative element. Since from two atoms, H and Cl, the _______ atom has the greatest EO, then the common electron pair shifts towards the _______ atom. Electronic circuit the formation of a covalent nonpolar bond in a hydrogen molecule looks like this:
N . + . Cl N : Cl ( on electronic circuit the shared electron pair is depicted closer to the more EO atom). If you replace the shared electron pair with a line, you get the structural formula of the molecule: H – Cl . In the structural formula, the displacement of a shared electron pair is shown using an arrow: HCl . As a result of the displacement of the electron pair, each atom in the molecule acquires a partial charge: hydrogen - a partial positive charge (it is easier for it to “breathe” after the displacement of the electron pair), chlorine - a partial negative charge (it pulls the “extra load” onto itself), i.e. two “poles” are formed. Therefore, this type of bond is called covalentpolar communication
P.S. If the number of unpaired electrons of atom1 is greater than the number of unpaired electrons of atom2, it is necessary to take such a number of atoms2 that the number of unpaired electrons coincides.
Do it!
Task 5. Draw the mechanism for the formation of polar covalent bonds in molecules HBr, H 2 S using electron-graphical, electronic and structural formulas. Next to the diagrams, indicate: a) the number of unpaired electrons of each atom; b) the number of electrons in the outer level of each atom; c) towards which atom the common electron pairs are displaced. Explain your answer.
If there is not enough space, use the reverse side of the sheet.
Teacher ratingIonic chemical bond
Explore!
An ionic bond is a chemical bond that occurs between ions due to the forces of electrostatic attraction.Ions – charged particles that are formed when an atom gives up or gains electrons. Atoms of a chemical element give up electrons only from the external energy level, and accordingly, they also accept electrons to the external energy level. If an atom of a chemical element gives up electrons, it turns into a positively charged ion (“rejoices” that it has thrown off its “burden”) For example: Na 0 – 1е Na + . Positively charged ions are calledcations . Charge of the cation equal to the number donated electrons.(!Atoms everyone metals always only give away electrons and always turn intocations !) If an atom of a chemical element gains electrons, it turns into a negatively charged ion (it has taken on an “extra load” and is therefore “upset”). For example: S 0 + 2 eS -2 . Negatively charged ions are calledanions . The charge of the anion is equal to the number of electrons accepted.
Do it!
Exercise 1. Write down the definitions in your notebook: a) ionic bond; b) ions. Make a diagram “Classification of ions”. Write down your explanations.
Task 2. Write down the cations and anions from the proposed series of ions in the diagram: Na+; S-2; N +5 ; Cl - ; Ca+2; Al+3; P-3; O-2; S +4 ; F - .
Task 3. Draw in your notebook and fill out Table 1.
Table 1.Atom of a chemical element
Explore!
Mechanism of ionic bond formation
Let us consider the mechanism of ionic bond formation using the example of lithium chloride LiCl. This compound is formed by lithium ions and chlorine ions. Let us show the formation of these ions using electron graphic formulas:
Li 0 Li +
1 s 2 2s 1 1s 2 (electronic configuration of the noble gas atom helium)
Cl 0 Cl - - 1е
Cl 0 Cl -
1 s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 3s 2 3p 6
An ionic bond occurs between the resulting lithium ions Li + and chlorine Cl - . It is clear that oppositely charged particles are attracted to each other and held together due to the forces of electrostatic attraction. The entire mechanism of ionic bond formation can be shown in the form of a brief diagram:
Li 0 – 1 eLi + ionic bond
Cl 0 +1 eCl -
Do it! Complete the tasks given on the back. in the notebook
Task 4.(Complete this task if you are on I option). Show the formation of an ionic bond between the Na and S atoms. Pay attention to the number of electrons that sodium will give up and the number of electrons that sulfur will accept... One sodium atom is clearly not enough... (This was a hint). After completing this task, answer the following questions:
How many sodium atoms are needed to form an ionic bond between it and sulfur? Why?
What noble gas configuration does the sulfur ion take?
Explain why the sodium atom gives up electrons? Why does a sulfur atom accept electrons?
Task 5.(Complete this task if you are on II option). Show the formation of an ionic bond between the Na and N atoms. Pay attention to the number of electrons that sodium will give up and the number of electrons that nitrogen will accept...One sodium atom is clearly not enough...(This was a hint). After completing this task, answer the following questions:
How many sodium atoms are needed to form an ionic bond between it and nitrogen? Why?
What noble gas configuration does the sodium ion take?
What noble gas configuration does the nitrogen ion take?
Explain why the sodium atom gives up electrons? Why does the nitrogen atom accept electrons?
Task 6. Draw the structure diagrams for the following ions: Mg +2; O-2; Ca+2; F - . Write abbreviated electronic formulas for them and indicate which noble gas configurations correspond to the configurations of these ions. Write formulas for all possible compounds that can be formed by these ions.
Task 7. What ions can have configuration 1 s 2 2s 2 2p 6 (electronic configuration of the neon atom). Give examples of at least three cations and three anions.
Homework! Learn the topic “Ionic chemical bonding”. Prepare for s/r on the topics “Electronegativity of chemical elements”, “Covalent chemical bond”, “Ionic bond”.
LIST OF REFERENCES USED
- Chemistry. Inorganic chemistry. 8th grade: textbook for general education. institutions/Rudzitis, Feldman - 13th edition-M: education, 2009- 176s
Problems for the section Chemical bonding and molecular structure are collected here.
Task 1. For sodium hydrogen sulfate, construct graphic formula and indicate the types of chemical bonds in the molecule: ionic, covalent, polar, covalent nonpolar, coordination, metallic, hydrogen.
Task 2. Construct a graphical formula for ammonium nitrite and indicate the types of chemical bonds in this molecule. Show which (which) connections are “broken” during dissociation. Explain what it is ? Give examples of its influence on the properties of a substance.
Solution. Ammonium nitrite - ionic bond
NH 4 NO 2 = NH 4 + +NO 2 -
N–H– covalently polar bond
Between NH 4 + and NO 2 — — ionic bond
Solution. CH3Br — . Covalent bond occurs between atoms with similar or equal electronegativity values. This bond can be thought of as the electrostatic attraction of the nuclei of two atoms to a common electron pair.
Unlike ionic compounds, molecules of covalent compounds are held together by "intermolecular forces", which are much weaker than chemical bonds. In this regard, covalent bonds are characterized saturability – formation of a limited number of connections.
It is known that atomic orbitals are oriented in space in a certain way, therefore, when a bond is formed, the overlap of electron clouds occurs in a certain direction. Those. such a property of a covalent bond is realized as focus.
Solution: Cloud overlap may occur different ways, in view of them various shapes. Distinguish σ-, π- and δ-bonds.
Sigma - communications are formed when clouds overlap along a line passing through the nuclei of atoms.
Pi – connections occur when clouds overlap on either side of the line connecting the nuclei of atoms.
Delta - connections are carried out by overlapping all four blades d - electron clouds located in parallel planes.
Sigma - communication more durable than Pi – connection.
C2H6 –sp 3 hybridization.
S-S— σ-bond (overlap 2sp 3 -2sp 3)
S–H— σ-bond (overlap of 2sp 3 -AO of carbon and 1s-AO of hydrogen)
C2H4 – sp 2 hybridization.
Double bond implemented by the presence of 2 types of communication - σ- and π-bonds(although it is depicted by two identical lines, their disparity should always be taken into account). σ-Bond is formed by the central overlap of sp 2 -hybridized orbitals, and π bond– with lateral overlap of the p-orbital lobes of neighboring sp 2 -hybridized carbon atoms. The formation of bonds in an ethylene molecule can be represented by the following diagram:
C=C- σ-bond (overlap 2sp 2 -2sp 2) and π-bond (2рz-2рz)
S–H— σ-bond (overlap of 2sp 2 -AO of carbon and 1s-AO of hydrogen)
C2H2 — sp hybridization
Triple bond is realized by a combination of σ- and two π-bonds formed by two sp-hybridized atoms.
σ-Bond occurs when the sp-hybridized orbitals of neighboring carbon atoms overlap centrally; π bonds are formed when the lobes overlap laterally ry-orbitals and pz-orbitals. The formation of bonds in the acetylene molecule H–C≡C–H can be depicted in the form of a diagram:
C≡C— σ-bond (2sp-2sp overlap);
π - connection (2рy-2рy);
π - connection (2рz-2рz);
S–H— σ-bond (overlap of 2sp-AO of carbon and 1s-AO of hydrogen).
Problem 5. What forces of intermolecular interaction are called dipole-dipole (orientational), inductive and dispersive? Explain the nature of these forces. What is the nature of the predominant intermolecular interaction forces in each of the following substances: H 2 O, HBr, Ar, N 2, NH 3?
Solution: Between molecules there may be electrostatic interaction. Most versatile - dispersive , because it is caused by the interaction of molecules with each other due to their instantaneous microdipoles. Their simultaneous appearance and disappearance in different molecules contributes to their attraction. In the absence of synchrony, molecules repel each other.
Orientation interaction appears between polar molecules. The greater the polarity of the molecule, the stronger the force of their attraction to each other, and thus the greater the orientational interaction.
Inductive interaction molecules arises due to their induced dipoles. When two molecules—polar and nonpolar—meet, the nonpolar molecule deforms, which contributes to the formation of a dipole in it. An induced dipole is capable of attraction to the permanent dipole of a polar molecule. Inductive interaction the greater, the greater the electrical moment and polarizability of the molecule.
The relative contribution of each type of interaction depends on the polarity and polarizability of the molecules. Thus, the higher the polarity of the molecule, the role is more important orientation forces; the greater the polarizability, the greater the influence of dispersion forces. Inductive forces depend on both factors, but themselves usually play a secondary role.
From these substances orientational and inductive interaction occurs in polar molecules - H 2 O and NH 3. Dispersion interaction- in non-polar and low-polar molecules - HBr, Ar, N2
Problem 6. Give two schemes for filling MOs during the interaction of two AOs with populations: a) electron + electron (1+1) and b) electron + vacant orbital (1+0). Determine the covalency of each atom and the bond order. What are the limits of binding energy? Which of the following bonds are in the hydrogen molecule H 2 and the molecular ion?
Solution :
A) Consider, for example, K 2 and Li 2. Participate in the formation of connections s – orbitals:
Contact order:
b) Consider, for example, K 2 + and Li 2 +. Participate in the formation of connections s – orbitals:
Contact order:
Covalency each atom is equal to 1.
Communication energy depends on the number of valence electrons: the fewer electrons, the lower the binding energy. In K 2 and Li 2 and K 2 + and Li 2 + the binding energy lies in the range of 200-1000 kJ/mol.
In the molecule H 2 a connection of the type is implemented electron + electron, A in the molecular ion H 2 + — electron + vacant orbital.
Task 7. Give the electronic configuration of the NO molecule using the MO method. How do the magnetic properties and bond strength change during the transition from the NO molecule to the NO + molecular ion?
The purpose of the lesson: consolidate students' knowledge of types of chemical bonds.
Lesson objectives:
1) repeat the main types of chemical bonds, properties and mechanism of their formation;
2) develop students’ skills in drawing up educational plans various types chemical bond;
3) to cultivate in students organization, independence, communication skills, the ability to generalize knowledge and apply it in practice.
Lesson type: lesson to consolidate knowledge.
Technologies used: control and corrective teaching technology, information and communication technology.
Equipment: table “Types of chemical bonds”, cards with tasks for individual work (3 levels), multi-level test tasks, interactive board, multimedia projector.
Forms educational activities: frontal, pair work, individual work, work with a textbook and additional. literature.
Lesson structure:
1. Organizational moment.
2. Repetition of the topic “Types of chemical bonds” (electronic presentation prepared by students).
3. Work in pairs using cards.
4. Individual work at the students' choice: oral control - conversation with a teacher or consultant, studying a topic in a textbook or additional literature, completing a test, doing independent work.
5. Summing up the lesson, homework.
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Preview:
Plan - outline open lesson chemistry in 11th grade.
Topic: “Types of chemical bonds.”
The purpose of the lesson: consolidate students' knowledge of types of chemical bonds.
Lesson objectives:
- repeat the main types of chemical bonds, properties and mechanism of their formation;
- develop students’ skills and abilities in drawing up schemes for the formation of various types of chemical bonds;
- to cultivate in students organization, independence, communication skills, the ability to generalize knowledge and apply it in practice.
Lesson type: lesson to consolidate knowledge.
Technologies used:control and corrective teaching technology, information and communication technology.
Equipment: table “Types of chemical bonds”, cards with tasks for individual work (3 levels), multi-level test tasks, interactive whiteboard, multimedia projector.
Forms of educational activities:frontal, pair work, individual work, work with a textbook and additional. literature.
Lesson structure:
- Organizing time.
- Review of the topic “Types of chemical bonds” (electronic presentation prepared by students).
- Work in pairs using cards.
- Individual work of the students' choice: oral control - conversation with a teacher or consultant, study of a topic in a textbook or additional literature, test work, independent work.
- Summing up the lesson, homework.
During the classes.
1 .Organizing time.Setting the lesson goal.
2. Repetition of the main types of chemical bonds. A group of students gives an electronic presentation “Types of chemical bonds.” A media projector and interactive whiteboard are used.
3. Work in pairs. Each pair of students receives a card with a task that they complete together, for example:
Card No. 1
1. Determine the type of chemical bond in substances and draw up bond formation schemes for these substances: MgBr 2, H 2 O, Na, H 2.
2. Determine the intermolecular chemical bond for the substance (CH 3OH) n , note the features in the properties of this substance in connection with this type of chemical bond.
4. Individual work of students of their choice.
The use of control and corrective teaching technology allows each student to develop his own educational trajectory. Students keep an activity record sheet where they mark each type of control.
After studying the topic, the student must undergo an oral interview with a teacher or consultant, complete a test and independent work. Only after this does he perform the final test. Consultants are appointed by the teacher, usually 2-3 people who mastered the topic earlier than others and passed all types of control.
Test (1st level)
1. A pair of elements between which an ionic chemical bond is formed:
A) carbon and sulfur; c) potassium and oxygen;
b) hydrogen and nitrogen; d) silicon and hydrogen.
2. Formula of a substance with a polar covalent bond:
A) NaCl; b) HCl; c) BaO; d) Ca 3 N 2.
3. Formula of a substance with a covalent nonpolar bond:
a) Na; b) Br 2; c) HBr; d) KCl.
4.The least polar bond is:
a) C – H; b) C – Cl; c) C – F; d) C – Br.
5. The strongest molecule is:
a) H 2; b) N 2; c) F 2; d) O 2.
6. The atomic crystal lattice has:
a) soda; b) water; c) diamond; d) paraffin.
7. The carbon atom has an oxidation state of -3 and a valence of IV when combined with the formula:
a) CO 2; b) C 2 H 6; c) CH 3 Cl; d) CaC 2.
8. A substance between the molecules of which there is a hydrogen bond:
a) ethane; b) sodium fluoride; c) carbon monoxide (II); d) ethanol.
9. The reasons for the sharp difference in the properties of water and hydrogen sulfide lie in the following features:
a) intramolecular bond; b) intermolecular bonds.
Test (2nd level)
1. Formula of a substance with an ionic bond:
a) NH 3; b) C 2 H 4; c) KH; d) CCl 4.
2. A covalent nonpolar bond is formed between atoms:
a) hydrogen and oxygen; c) hydrogen and chlorine;
b) hydrogen and phosphorus; d) magnesium.
3. The most polar relationship is:
a) N – C; b) N – O; c) H – S; d) H – I.
4. The number of sigma and pi bonds in the substance propene, respectively:
a) 7-sigma, 2-pi; c) 6-sigma, 2-pi
b) 8-sigma, 1-pi; d) 8-sigma, 2-pi.
5. The strongest bonds in a molecule of a substance whose formula is:
a) H 2 S; b) H 2 Se; c) H 2 O; d) H 2 Te.
6. The nitrogen atom has a valency of III and an oxidation state of 0 in a molecule of a substance whose formula is:
a)) NH 3; b) N 2; c) CH 3 NO 2; d) N 2 O 3.
7. The molecular structure has a substance with the formula:
a) CH 4; b) NaOH; c) SiO 2; d) Al.
8. A hydrogen bond is formed between:
a) water molecules; c) hydrogen molecules;
b) hydrocarbon molecules; d) metal atoms and hydrogen atoms.
9. Which connection has direction:
a) ionic; b) covalent; c) metal.
Test (3rd level)
1. Chemical bonds in substances whose formulas are CH 4 and CaCl 2 respectively:
a) ionic and covalent polar;
b) covalent polar and ionic;
c) covalent nonpolar and ionic;
d) covalent polar and metallic.
2. The polarity of the bond is greater in a substance with the formula:
a) Br 2; b) LiBr; c) HBr; d) KBr.
3. Ionic nature of bonds in a series of compounds
Li 2 O - Na 2 O – K 2 O – Rb 2 O:
a) increases; c) does not change;
b) decreases; d) first decreases, then increases.
4. There is a covalent bond between atoms, formed by a donor-acceptor mechanism in a substance whose formula is:
a) Al(OH) 3; b) Cl; c) C 2 H 5 OH; d) C 6 H 12 O 6.
5. A pair of formulas for substances that contain only sigma bonds:
a) CH 4 and O 2; b) C 2 H 5 OH and H 2 O; c) N 2 and CO 2; d) HBr and C 2 H 4
6. The strongest connection of the given ones:
a) C – Cl; b) C – F; c) C – Br; d) C – I.
7. The valence and degree of nitrogen in ammonium chloride are respectively equal:
a) IV and +4; b) IV and -2; c) III and +2; d) IV and -3.
8. General property for substances with a molecular crystal lattice:
a) solubility in water; c) electrical conductivity of solutions;
b) high boiling point; d) volatility.
9. The formation of hydrogen bonds can be explained by:
a) solubility acetic acid in water;
b) acidic properties of ethanol;
V) high temperature melting of many metals;
d) insolubility of methane in water.
5. Summing up.So, today we have repeated the main types of chemical bonds, their properties and the mechanism of formation. Review what you learned and what questions you found difficult. If necessary, work through § 6 from the textbook again.
Homework:
Repeat § 6;
Execute exercise 1-3 on p.34.
