Let's talk about solids. Solids can be divided into two large groups: amorphous And crystalline. We will separate them according to the principle of whether there is order or not.
IN amorphous substances the molecules are arranged randomly. There are no patterns in their spatial arrangement. Essentially, amorphous substances are very viscous liquids, so viscous that they are solid.
Hence the name: “a-” – negative particle, “morphe” – form. Amorphous substances include: glass, resins, wax, paraffin, soap.
The lack of order in the arrangement of particles causes physical properties amorphous bodies: they do not have fixed melting points. As they heat up, their viscosity gradually decreases, and they also gradually turn into a liquid state.
In contrast to amorphous substances, there are crystalline substances. The particles of a crystalline substance are spatially ordered. This correct structure of the spatial arrangement of particles in a crystalline substance is called crystal lattice .
Unlike amorphous bodies, crystalline substances have fixed melting points.
Depending on what particles are in lattice nodes, and what connections hold them together differentiate them: molecular, atomic, ionic And metal grates.
Why is it fundamentally important to know what kind of crystal lattice a substance has? What does it define? All. The structure determines how chemical and physical properties of a substance.
The simplest example: DNA. In all organisms on earth it is built from the same set structural components: four types of nucleotides. And what a variety of life. This is all determined by structure: the order in which these nucleotides are arranged.
Molecular crystal lattice.
A typical example is water in a solid state (ice). Entire molecules are located at lattice sites. And keep them together intermolecular interactions: hydrogen bonds, van der Waals forces.
These bonds are weak, so the molecular lattice is the most fragile, the melting point of such substances is low.
Good diagnostic sign: if a substance has normal conditions liquid or gaseous state and/or has an odor - then most likely this substance has a molecular crystal lattice. After all, the liquid and gaseous states are a consequence of the fact that the molecules on the surface of the crystal do not adhere well (the bonds are weak). And they are “blown away.” This property is called volatility. And the deflated molecules, diffusing in the air, reach our olfactory organs, which is subjectively felt as a smell.
They have a molecular crystal lattice:
- Some simple substances of non-metals: I 2, P, S (that is, all non-metals that do not have an atomic lattice).
- Almost all organic matter (except salts).
- And as mentioned earlier, substances under normal conditions are liquid, or gaseous (being frozen) and/or odorless (NH 3, O 2, H 2 O, acids, CO 2).
Atomic crystal lattice.
In the nodes of the atomic crystal lattice, in contrast to the molecular one, there are individual atoms. It turns out that the lattice is held together by covalent bonds (after all, they are the ones that bind neutral atoms).
A classic example is the standard of strength and hardness - diamond (by its chemical nature it is a simple substance - carbon). Contacts: covalent nonpolar, since the lattice is formed only by carbon atoms.
But, for example, in a quartz crystal ( chemical formula of which SiO 2) are Si and O atoms. Therefore, the bonds covalent polar.
Physical properties of substances with an atomic crystal lattice:
- strength, hardness
- high melting points (refractoriness)
- non-volatile substances
- insoluble (neither in water nor in other solvents)
All these properties are due to the strength of covalent bonds.
There are few substances in an atomic crystal lattice. There is no particular pattern, so you just need to remember them:
- Allotropic modifications of carbon (C): diamond, graphite.
- Boron (B), silicon (Si), germanium (Ge).
- Only two allotropic modifications of phosphorus have an atomic crystal lattice: red phosphorus and black phosphorus. (white phosphorus has a molecular crystal lattice).
- SiC – carborundum (silicon carbide).
- BN – boron nitride.
- Silica, rock crystal, quartz, river sand - all these substances have the composition SiO 2.
- Corundum, ruby, sapphire - these substances have the composition Al 2 O 3.
Surely the question arises: C is both diamond and graphite. But they are completely different: graphite is opaque, stains, conducts electricity, and diamond is transparent, does not stain and does not conduct current. They differ in structure.
Both are atomic lattice, but different. Therefore, the properties are different.
Ionic crystal lattice.
Classic example: salt: NaCl. At the lattice nodes there are individual ions: Na + and Cl – . The lattice is held in place by electrostatic forces of attraction between the ions (“plus” is attracted to “minus”), that is ionic bond.
Ionic crystal lattices are quite strong, but fragile; the melting temperatures of such substances are quite high (higher than those of metallic lattices, but lower than those of substances with an atomic lattice). Many are soluble in water.
As a rule, there are no problems with determining the ionic crystal lattice: where there is an ionic bond, there is an ionic crystal lattice. This: all salts, metal oxides, alkalis(and other basic hydroxides).
Metal crystal lattice.
The metal grating is sold in simple substances metals. Earlier we said that all the splendor of the metallic bond can only be understood in conjunction with the metallic crystal lattice. The hour has come.
The main property of metals: electrons on external energy level They are poorly held, so they are easily given away. Having lost an electron, the metal turns into a positively charged ion - a cation:
Na 0 – 1e → Na +
In a metal crystal lattice, processes of electron release and gain constantly occur: an electron is torn away from a metal atom at one lattice site. A cation is formed. The detached electron is attracted by another cation (or the same one): a neutral atom is formed again.
The nodes of a metal crystal lattice contain both neutral atoms and metal cations. And free electrons travel between the nodes:
These free electrons are called electron gas. They determine the physical properties of simple metal substances:
- thermal and electrical conductivity
- metallic shine
- malleability, ductility
This is a metallic bond: metal cations are attracted to neutral atoms and free electrons “glue” it all together.
How to determine the type of crystal lattice.
P.S. There's something in school curriculum and the Unified State Exam program on this topic is something with which we do not entirely agree. Namely: the generalization that any metal-nonmetal bond is an ionic bond. This assumption was deliberately made, apparently to simplify the program. But this leads to distortion. The boundary between ionic and covalent bonds is arbitrary. Each bond has its own percentage of “ionicity” and “covalency”. The bond with a low-active metal has a small percentage of “ionicity”; it is more like a covalent one. But according to the Unified State Exam program, it is “rounded” towards the ionic one. This gives rise to sometimes absurd things. For example, Al 2 O 3 is a substance with an atomic crystal lattice. What kind of ionicity are we talking about here? Only a covalent bond can hold atoms together in this way. But according to the metal-non-metal standard, we classify this bond as ionic. And we get a contradiction: the lattice is atomic, but the bond is ionic. This is what oversimplification leads to.
The bonds between ions in a crystal are very strong and stable. Therefore, substances with an ionic lattice have high hardness and strength, are refractory and nonvolatile.
Substances with an ionic crystal lattice have the following properties:
1. Relatively high hardness and strength;
2. Fragility;
3. Heat resistance;
4. Refractoriness;
5. Non-volatility.
Examples: salts - sodium chloride, potassium carbonate, bases - calcium hydroxide, sodium hydroxide.
4. Mechanism of covalent bond formation (exchange and donor-acceptor).
Each atom strives to complete its outermost electron level to reduce potential energy. Therefore, the nucleus of one atom is attracted to itself by the electron density of another atom, and vice versa, the electron clouds of two neighboring atoms overlap.
Demonstration of the application and diagram of the formation of a covalent nonpolar chemical bond in a hydrogen molecule. (Students write down and sketch diagrams).
Conclusion: The connection between atoms in a hydrogen molecule is carried out through a common electron pair. Such a bond is called covalent.
What type of bond is called a nonpolar covalent bond? (Textbook p. 33).
Drawing up electronic formulas of molecules of simple substances of non-metals:
CI CI - electronic formula of the chlorine molecule,
CI -- CI is the structural formula of a chlorine molecule.
N N is the electronic formula of the nitrogen molecule,
N ≡ N is the structural formula of a nitrogen molecule.
Electronegativity. Covalent polar and nonpolar bonds. Multiplicity of covalent bond.
But molecules can also form different non-metal atoms, and in this case the common electron pair will shift to a more electronegative chemical element.
Study the textbook material on page 34
Conclusion: Metals have more low value electronegativity than nonmetals. And it is very different between them.
Demonstration of the formation of a polar covalent bond in a hydrogen chloride molecule.
The shared electron pair is shifted to chlorine, as it is more electronegative. So this is a covalent bond. It is formed by atoms whose electronegativity does not differ much, so it is a polar covalent bond.
Drawing up electronic formulas of hydrogen iodide and water molecules:
H J is the electronic formula of the hydrogen iodide molecule,
H → J is the structural formula of the hydrogen iodide molecule.
HO - electronic formula of a water molecule,
H →O - structural formula of a water molecule.
Independent work with a textbook: write down the definition of electronegativity.
Molecular and atomic crystal lattices. Properties of substances with molecular and atomic crystal lattices
Independent work with the textbook.
Questions for self-control
Atom, what chemical element has a core charge of +11
– Write down the diagram of the electronic structure of the sodium atom
– Is the outer layer complete?
– How to complete filling of the electronic layer?
– Draw up a diagram of electron donation
– Compare the structure of the atom and ion of sodium
Compare the structure of the atom and ion of the inert gas neon.
Determine the atom of which element with the number of protons 17.
– Write down the diagram of the electronic structure of an atom.
– Is the layer complete? How to achieve this.
– Draw up a diagram of the completion of the electron layer of chlorine.
Group assignment:
Group 1-3: Compose electronic and structural formulas molecules of substances and indicate the type of bond Br 2; NH3.
Groups 4-6: Make up electronic and structural formulas of the molecules of substances and indicate the type of bond F 2; HBr.
Two students work at an additional board with the same task for a sample for self-test.
Oral survey.
1. Define the concept of “electronegativity”.
2. What does the electronegativity of an atom depend on?
3. How does the electronegativity of atoms of elements change in periods?
4. How does the electronegativity of atoms of elements in the main subgroups change?
5. Compare the electronegativity of metal and non-metal atoms. Do the methods of completing the outer electron layer differ between metal and nonmetal atoms? What are the reasons for this?
7. What chemical elements are capable of donating electrons and accepting electrons?
What happens between atoms when they give and take electrons?
What are the particles formed from an atom as a result of the loss or gain of electrons called?
8. What happens when metal and non-metal atoms meet?
9. How is an ionic bond formed?
10. A chemical bond formed due to the formation of shared electron pairs is called...
11. Covalent bonds can be... and...
12. What are the similarities between polar covalent and nonpolar covalent bonds? What determines the polarity of the connection?
13. What is the difference between polar covalent and nonpolar covalent bonds?
LESSON PLAN No. 8
Discipline: Chemistry.
Subject: Metal connection. Aggregate states of substances and hydrogen bonding .
Purpose of the lesson: Form a concept of chemical bonds using the example of a metal bond. Achieve an understanding of the mechanism of bond formation.
Planned results
Subject: formation of a person’s horizons and functional literacy for solving practical problems; ability to process and explain results; willingness and ability to apply cognitive methods in solving practical problems;
Metasubject: the use of various sources to obtain chemical information, the ability to assess its reliability in order to achieve good results V professional field;
Personal: the ability to use the achievements of modern chemical science and chemical technologies to improve one’s own intellectual development in the chosen field professional activity;
Standard time: 2 hours
Type of lesson: Lecture.
Lesson plan:
1. Metal connection. Metal crystal lattice and metal chemical bond.
2. Physical properties of metals.
3. Aggregate states of substances. The transition of a substance from one state of aggregation to another.
4. Hydrogen bond
Equipment: Periodic table of chemical elements, crystal lattice, handout.
Literature:
1. Chemistry 11th grade: textbook. for general education organizations G.E. Rudzitis, F.G. Feldman. – M.: Education, 2014. -208 p.: ill..
2. Chemistry for professions and technical specialties: a textbook for students. institutions prof. education / O.S. Gabrielyan, I.G. Ostroumov. – 5th ed., erased. – M.: Publishing Center “Academy”, 2017. – 272 pp., with colors. ill.
Teacher: Tubaltseva Yu.N.
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Lesson type: Combined.
The main goal of the lesson: To give students specific ideas about amorphous and crystalline substances, types of crystal lattices, to establish the relationship between the structure and properties of substances.
Lesson objectives.
Educational: to form concepts about the crystalline and amorphous state of solids, to familiarize students with various types of crystal lattices, to establish the dependence of the physical properties of a crystal on the nature of the chemical bond in the crystal and the type of crystal lattice, to give students basic ideas about the influence of the nature of chemical bonds and types of crystal lattices on properties of matter, give students an idea of the law of constancy of composition.
Educational: continue to form the worldview of students, consider the mutual influence of the components of whole-structural particles of substances, as a result of which new properties appear, develop the ability to organize their educational work, and observe the rules of working in a team.
Developmental: develop the cognitive interest of schoolchildren using problem situations; improve students’ abilities to establish the cause-and-effect dependence of the physical properties of substances on chemical bonds and the type of crystal lattice, to predict the type of crystal lattice based on the physical properties of the substance.
Equipment: Periodic table of D.I. Mendeleev, collection “Metals”, non-metals: sulfur, graphite, red phosphorus, oxygen; Presentation “Crystal lattices”, models of crystal lattices of different types (table salt, diamond and graphite, carbon dioxide and iodine, metals), samples of plastics and products made from them, glass, plasticine, resins, wax, chewing gum, chocolate, computer, multimedia installation, video experiment “Sublimation of benzoic acid”.
During the classes
1. Organizational moment.
The teacher welcomes students and records those who are absent.
Then he tells the topic of the lesson and the purpose of the lesson. Students write down the topic of the lesson in their notebook. (Slide 1, 2).
2. Checking homework
(2 students at the blackboard: Determine the type of chemical bond for substances with the formulas:
1) NaCl, CO 2, I 2; 2) Na, NaOH, H 2 S (write the answer on the board and include it in the survey).
3. Analysis of the situation.
Teacher: What does chemistry study? Answer: Chemistry is the science of substances, their properties and transformations of substances.
Teacher: What is a substance? Answer: Matter is what the physical body is made of. (Slide 3).
Teacher: What states of matter do you know?
Answer: There are three states of aggregation: solid, liquid and gaseous. (Slide 4).
Teacher: Give examples of substances that can exist in all three states of aggregation at different temperatures.
Answer: Water. At normal conditions water is in a liquid state, when the temperature drops below 0 0 C, water turns into a solid state - ice, and when the temperature rises to 100 0 C we get water vapor (gaseous state).
Teacher (addition): Any substance can be obtained in solid, liquid and gaseous form. In addition to water, these are metals that, under normal conditions, are in a solid state, when heated, they begin to soften, and at a certain temperature (t pl) they turn into a liquid state - they melt. With further heating, to the boiling point, the metals begin to evaporate, i.e. go into a gaseous state. Any gas can be converted into a liquid and solid state by lowering the temperature: for example, oxygen, which at a temperature (-194 0 C) turns into a blue liquid, and at a temperature (-218.8 0 C) solidifies into a snow-like mass consisting of crystals of blue color. Today in class we will look at the solid state of matter.
Teacher: Name what solid substances are on your tables.
Answer: Metals, plasticine, table salt: NaCl, graphite.
Teacher: What do you think? Which of these substances is excess?
Answer: Plasticine.
Teacher: Why?
Assumptions are made. If students find it difficult, then with the help of the teacher they come to the conclusion that plasticine, unlike metals and sodium chloride, does not have a certain melting point - it (plasticine) gradually softens and turns into a fluid state. Such, for example, is chocolate that melts in the mouth, or chewing gum, as well as glass, plastics, resins, wax (when explaining, the teacher shows the class samples of these substances). Such substances are called amorphous. (slide 5), and metals and sodium chloride are crystalline. (Slide 6).
Thus, two types of solids are distinguished : amorphous and crystalline. (slide7).
1) Amorphous substances do not have a specific melting point and the arrangement of particles in them is not strictly ordered.
Crystalline substances have a strictly defined melting point and, most importantly, are characterized by the correct arrangement of the particles from which they are built: atoms, molecules and ions. These particles are located at strictly defined points in space, and if these nodes are connected by straight lines, then a spatial frame is formed - crystal cell.
The teacher asks problematic issues
How to explain the existence of solids with such different properties?
2) Why do crystalline substances split in certain planes upon impact, while amorphous substances do not have this property?
Listen to the students' answers and lead them to conclusion:
The properties of substances in the solid state depend on the type of crystal lattice (primarily on what particles are in its nodes), which, in turn, is determined by the type of chemical bond in a given substance.
Checking homework:
1) NaCl – ionic bond,
CO 2 – covalent polar bond
I 2 – covalent nonpolar bond
2) Na – metal bond
NaOH - ionic bond between Na + ion - (O and H covalent)
H 2 S - covalent polar
Frontal survey.
- Which bond is called ionic?
- What kind of bond is called covalent?
- Which bond is called a polar covalent bond? non-polar?
- What is electronegativity called?
Conclusion: There is a logical sequence, the relationship of phenomena in nature: Structure of the atom -> EO -> Types of chemical bonds -> Type of crystal lattice -> Properties of substances . (slide 10).
Teacher: Depending on the type of particles and the nature of the connection between them, they distinguish four types of crystal lattices: ionic, molecular, atomic and metallic. (Slide 11).
The results are presented in the following table - a sample table at the students’ desks. (see Appendix 1). (Slide 12).
Ionic crystal lattices
Teacher: What do you think? For substances with what type of chemical bond will this type of lattice be characteristic?
Answer: Substances with ionic chemical bonds will be characterized by an ionic lattice.
Teacher: What particles will be at the lattice nodes?
Answer: Jonah.
Teacher: What particles are called ions?
Answer: Ions are particles that have a positive or negative charge.
Teacher: What are the compositions of ions?
Answer: Simple and complex.
Demonstration - model of sodium chloride (NaCl) crystal lattice.
Teacher's explanation: At the nodes of the sodium chloride crystal lattice there are sodium and chlorine ions.
In NaCl crystals there are no individual sodium chloride molecules. The entire crystal should be considered as a giant macromolecule consisting of equal number ions Na + and Cl -, Na n Cl n, where n is a large number.
The bonds between ions in such a crystal are very strong. Therefore, substances with an ionic lattice have a relatively high hardness. They are refractory, non-volatile, and fragile. Their melts conduct electric current (Why?) and easily dissolve in water.
Ionic compounds are binary compounds of metals (I A and II A), salts, and alkalis.
Atomic crystal lattices
Demonstration of crystal lattices of diamond and graphite.
The students have graphite samples on the table.
Teacher: What particles will be located at the nodes of the atomic crystal lattice?
Answer: At the nodes of the atomic crystal lattice there are individual atoms.
Teacher: What chemical bond will arise between atoms?
Answer: Covalent chemical bond.
Teacher's explanations.
Indeed, at the sites of atomic crystal lattices there are individual atoms connected to each other by covalent bonds. Since atoms, like ions, can be arranged differently in space, crystals of different shapes are formed.
Atomic crystal lattice of diamond
There are no molecules in these lattices. The entire crystal should be considered as a giant molecule. An example of substances with this type of crystal lattices are allotropic modifications of carbon: diamond, graphite; as well as boron, silicon, red phosphorus, germanium. Question: What are these substances in composition? Answer: Simple in composition.
Atomic crystal lattices have not only simple, but also complex ones. For example, aluminum oxide, silicon oxide. All these substances have very high melting points (diamond has over 3500 0 C), are strong and hard, non-volatile, and practically insoluble in liquids.
Metal crystal lattices
Teacher: Guys, you have a collection of metals on your tables, let’s look at these samples.
Question: What chemical bond is characteristic of metals?
Answer: Metal. Bonding in metals between positive ions through shared electrons.
Question: What general physical properties are characteristic of metals?
Answer: Luster, electrical conductivity, thermal conductivity, ductility.
Question: Explain what is the reason that so many different substances have the same physical properties?
Answer: Metals have a single structure.
Demonstration of models of metal crystal lattices.
Teacher's explanation.
Substances with metallic bonds have metallic crystal lattices
At the sites of such lattices there are atoms and positive ions of metals, and valence electrons move freely in the volume of the crystal. The electrons electrostatically attract positive metal ions. This explains the stability of the lattice.
Molecular crystal lattices
The teacher demonstrates and names the substances: iodine, sulfur.
Question: What do these substances have in common?
Answer: These substances are non-metals. Simple in composition.
Question: What is the chemical bond inside molecules?
Answer: The chemical bond inside molecules is covalent nonpolar.
Question: What physical properties are characteristic of them?
Answer: Volatile, fusible, slightly soluble in water.
Teacher: Let's compare the properties of metals and non-metals. Students answer that the properties are fundamentally different.
Question: Why are the properties of non-metals very different from the properties of metals?
Answer: Metals have metallic bonds, while non-metals have covalent, nonpolar bonds.
Teacher: Therefore, the type of lattice is different. Molecular.
Question: What particles are located at lattice points?
Answer: Molecules.
Demonstration of crystal lattices of carbon dioxide and iodine.
Teacher's explanation.
Molecular crystal lattice
As we see, not only solids can have a molecular crystal lattice. simple substances: noble gases, H 2, O 2, N 2, I 2, O 3, white phosphorus P 4, but also complex: solid water, solid hydrogen chloride and hydrogen sulfide. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).
The lattice sites contain nonpolar or polar molecules. Despite the fact that the atoms inside the molecules are connected by strong covalent bonds, weak intermolecular forces act between the molecules themselves.
Conclusion: The substances are fragile, have low hardness, a low melting point, are volatile, and are capable of sublimation.
Question : Which process is called sublimation or sublimation?
Answer : The transition of a substance from a solid state of aggregation directly to a gaseous state, bypassing the liquid state, is called sublimation or sublimation.
Demonstration of the experiment: sublimation of benzoic acid (video experiment).
Working with a completed table.
Appendix 1. (Slide 17)
Crystal lattices, type of bond and properties of substances
| Grille type | Types of particles at lattice sites |
Type of connection between particles | Examples of substances | Physical properties of substances |
| Ionic | Ions | Ionic – strong bond | Salts, halides (IA, IIA), oxides and hydroxides of typical metals | Solid, strong, non-volatile, brittle, refractory, many soluble in water, melts conduct electric current |
| Nuclear | Atoms | 1. Covalent nonpolar - the bond is very strong 2. Covalent polar - the bond is very strong |
Simple substances A: diamond(C), graphite(C), boron(B), silicon(Si).
Complex substances: aluminum oxide (Al 2 O 3), silicon oxide (IY)-SiO 2 |
Very hard, very refractory, durable, non-volatile, insoluble in water |
| Molecular | Molecules | Between molecules there are weak forces of intermolecular attraction, but inside the molecules there is a strong covalent bond | Solids under special conditions that under normal conditions are gases or liquids (O 2 , H 2 , Cl 2 , N 2 , Br 2 , H 2 O, CO 2, HCl); sulfur, white phosphorus, iodine; organic matter |
Fragile, volatile, fusible, capable of sublimation, have low hardness |
| Metal | Atom ions | Metal of different strengths | Metals and alloys | Malleable, shiny, ductile, thermally and electrically conductive |
Question: Which type of crystal lattice from those discussed above is not found in simple substances?
Answer: Ionic crystal lattices.
Question: What crystal lattices are characteristic of simple substances?
Answer: For simple substances - metals - a metal crystal lattice; for non-metals - atomic or molecular.
Working with the Periodic Table of D.I.Mendeleev.
Question: Where are the metal elements located in the Periodic Table and why? Non-metal elements and why?
Answer: If you draw a diagonal from boron to astatine, then in the lower left corner of this diagonal there will be metal elements, because at the last energy level they contain from one to three electrons. These are elements I A, II A, III A (except boron), as well as tin and lead, antimony and all elements of secondary subgroups.
Non-metal elements are located in the upper right corner of this diagonal, because at the last energy level they contain from four to eight electrons. These are the elements IY A, Y A, YI A, YII A, YIII A and boron.
Teacher: Let's find non-metal elements whose simple substances have an atomic crystal lattice (Answer: C, B, Si) and molecular ( Answer: N, S, O , halogens and noble gases ).
Teacher: Formulate a conclusion on how you can determine the type of crystal lattice of a simple substance depending on the position of the elements in D.I. Mendeleev’s Periodic Table.
Answer: For metal elements that are in I A, II A, IIIA (except for boron), as well as tin and lead, and all elements of secondary subgroups in a simple substance, the type of lattice is metal.
For the nonmetal elements IY A and boron in a simple substance, the crystal lattice is atomic; and the elements Y A, YI A, YII A, YIII A in simple substances have a molecular crystal lattice.
We continue to work with the completed table.
Teacher: Look carefully at the table. What pattern can be observed?
We listen carefully to the students’ answers, and then together with the class we draw the following conclusion:
There is the following pattern: if the structure of substances is known, then their properties can be predicted, or vice versa: if the properties of substances are known, then the structure can be determined. (Slide 18).
Teacher: Look carefully at the table. What other classification of substances can you suggest?
If the students find it difficult, the teacher explains that substances can be divided into substances of molecular and non-molecular structure. (Slide 19).
Substances molecular structure consist of molecules.
Substances of non-molecular structure consist of atoms and ions.
Law of Constancy of Composition
Teacher: Today we will get acquainted with one of the basic laws of chemistry. This is the law of constancy of composition, which was discovered by the French chemist J.L. Proust. The law is valid only for substances of molecular structure. Currently, the law reads like this: “Molecular chemical compounds, regardless of the method of their preparation, have a constant composition and properties.” But for substances with a non-molecular structure this law is not always true.
The theoretical and practical significance of the law is that on its basis the composition of substances can be expressed using chemical formulas (for many substances of non-molecular structure, the chemical formula shows the composition of not a real existing, but a conditional molecule).
Conclusion: The chemical formula of a substance contains a lot of information.(Slide 21)
For example, SO 3:
1. The specific substance is sulfur dioxide, or sulfur oxide (YI).
2.Type of substance - complex; class - oxide.
3. Qualitative composition - consists of two elements: sulfur and oxygen.
4. Quantitative composition - the molecule consists of 1 sulfur atom and 3 oxygen atoms.
5.Relative molecular weight - M r (SO 3) = 32 + 3 * 16 = 80.
6. Molar mass - M(SO 3) = 80 g/mol.
7. Lots of other information.
Consolidation and application of acquired knowledge
(Slide 22, 23).
Tic-tac-toe game: cross out substances that have the same crystal lattice vertically, horizontally, diagonally.
Reflection.
The teacher asks the question: “Guys, what new did you learn in class?”
Summing up the lesson
Teacher: Guys, let's summarize the main results of our lesson - answer the questions.
1. What classifications of substances did you learn?
2. How do you understand the term crystal lattice?
3. What types of crystal lattices do you now know?
4. What regularities in the structure and properties of substances did you learn about?
5. In what state of aggregation do substances have crystal lattices?
6. What basic law of chemistry did you learn in class?
Homework: §22, notes.
1. Make up the formulas of the substances: calcium chloride, silicon oxide (IY), nitrogen, hydrogen sulfide.
Determine the type of crystal lattice and try to predict what the melting points of these substances should be.
2. Creative task -> make up questions for the paragraph.
The teacher thanks you for the lesson. Gives marks to students.
When carrying out many physical and chemical reactions, a substance passes into a solid state of aggregation. In this case, molecules and atoms tend to arrange themselves in such a spatial order in which the forces of interaction between particles of matter would be maximally balanced. This is how strength is achieved solid. Atoms, once occupying a certain position, perform small oscillatory movements, the amplitude of which depends on temperature, but their position in space remains fixed. The forces of attraction and repulsion balance each other at a certain distance.
Modern ideas about the structure of matter
Modern science states that an atom consists of a charged nucleus, which carries a positive charge, and electrons, which carry negative charges. At a speed of several thousand trillion revolutions per second, electrons rotate in their orbits, creating an electron cloud around the nucleus. The positive charge of the nucleus is numerically equal to negative charge electrons. Thus, the atom of the substance remains electrically neutral. Possible interactions with other atoms occur when electrons are detached from their native atom, thereby disturbing the electrical balance. In one case, the atoms are arranged in a certain order, which is called a crystal lattice. In another, due to the complex interaction of nuclei and electrons, they combine into molecules various types and complexity.
Definition of crystal lattice
In total Various types Crystal lattices of substances are networks with different spatial orientations, at the nodes of which ions, molecules or atoms are located. This stable geometric spatial position is called the crystal lattice of the substance. The distance between nodes of one crystal cell is called the identity period. The spatial angles at which the cell nodes are located are called parameters. According to the method of constructing bonds, crystal lattices can be simple, base-centered, face-centered, and body-centered. If the particles of matter are located only in the corners of the parallelepiped, such a lattice is called simple. An example of such a lattice is shown below:
If, in addition to the nodes, the particles of the substance are located in the middle of the spatial diagonals, then this arrangement of particles in the substance is called a body-centered crystal lattice. This type is clearly shown in the figure.
If, in addition to the nodes at the vertices of the lattice, there is a node at the place where the imaginary diagonals of the parallelepiped intersect, then you have a face-centered type of lattice.
Types of crystal lattices
The different microparticles that make up a substance determine the different types of crystal lattices. They can determine the principle of building connections between microparticles inside a crystal. Physical types of crystal lattices are ionic, atomic and molecular. This also includes various types of metal crystal lattices. Studying the principles internal structure Chemistry deals with elements. The types of crystal lattices are presented in more detail below.
Ionic crystal lattices
These types of crystal lattices are present in compounds with an ionic type of bond. In this case, lattice sites contain ions with opposite electrical charges. Thanks to electromagnetic field, the forces of interionic interaction turn out to be quite strong, and this determines the physical properties of the substance. Common characteristics are refractoriness, density, hardness and the ability to conduct electric current. Ionic types of crystal lattices are found in substances such as table salt, potassium nitrate and others.
Atomic crystal lattices
This type of structure of matter is inherent in elements whose structure is determined by covalent chemical bonds. Types of crystal lattices of this kind contain individual atoms at the nodes, connected to each other by strong covalent bonds. This type of bond occurs when two identical atoms “share” electrons, thereby forming a common pair of electrons for neighboring atoms. Thanks to this interaction, covalent bonds bind atoms evenly and strongly in a certain order. Chemical elements that contain atomic types of crystal lattices are hard, have a high melting point, are poor conductors of electricity, and are chemically inactive. Classic examples of elements with a similar internal structure include diamond, silicon, germanium, and boron.
Molecular crystal lattices
Substances that have a molecular type of crystal lattice are a system of stable, interacting, closely packed molecules that are located at the nodes of the crystal lattice. In such compounds, the molecules retain their spatial position in the gaseous, liquid and solid phases. At the nodes of the crystal, molecules are held together by weak van der Waals forces, which are tens of times weaker than the ionic interaction forces.
The molecules that form a crystal can be either polar or nonpolar. Due to the spontaneous movement of electrons and vibrations of nuclei in molecules, the electrical equilibrium can shift - this is how an instantaneous electric dipole moment arises. Appropriately oriented dipoles create attractive forces in the lattice. Carbon dioxide and paraffin are typical examples of elements with a molecular crystal lattice.
Metal crystal lattices
A metal bond is more flexible and ductile than an ionic bond, although it may seem that both are based on the same principle. The types of crystal lattices of metals explain their typical properties - such as mechanical strength, thermal and electrical conductivity, and fusibility.
A distinctive feature of a metal crystal lattice is the presence of positively charged metal ions (cations) at the sites of this lattice. Between the nodes there are electrons that are directly involved in the creation electric field around the grate. The number of electrons moving around within this crystal lattice is called electron gas.
In the absence of an electric field, free electrons perform chaotic motion, randomly interacting with lattice ions. Each such interaction changes the momentum and direction of motion of the negatively charged particle. With their electric field, electrons attract cations to themselves, balancing their mutual repulsion. Although electrons are considered free, their energy is not enough to leave the crystal lattice, so these charged particles are constantly within its boundaries.
The presence of an electric field gives the electron gas additional energy. The connection with ions in the crystal lattice of metals is not strong, so electrons easily leave its boundaries. Electrons move along lines of force, leaving behind positively charged ions.
conclusions
Chemistry attaches great importance to the study of the internal structure of matter. The types of crystal lattices of various elements determine almost the entire range of their properties. By influencing crystals and changing their internal structure, it is possible to achieve enhancement required properties substances and remove unwanted ones, transform chemical elements. Thus, studying the internal structure of the surrounding world can help to understand the essence and principles of the structure of the universe.
| Lattice type | Characteristic |
| Ionic | Consist of ions. They form substances with ionic bonds. They have high hardness, brittleness, are refractory and low-volatile, easily dissolve in polar liquids, and are dielectrics. Melting of ionic crystals leads to a violation of the geometrically correct orientation of the ions relative to each other and a weakening of the bond strength between them. Therefore, their melts (solutions) conduct electric current. Ionic crystal lattices form many salts, oxides, and bases. |
| Atomic (covalent) | The nodes contain atoms that are connected to each other by covalent bonds. There are many atomic crystals. All of them have a high melting point, are insoluble in liquids, have high strength, hardness, and a wide range of electrical conductivity. Atomic crystal lattices are formed by elements of groups III and IV of the main subgroups (Si, Ge, B, C). |
Continuation of the table. Z4
| Molecular | They consist of molecules (polar and non-polar) that are connected to each other by weak hydrogen, intermolecular and electrostatic forces. Therefore, molecular crystals have low hardness, low temperatures melting, are slightly soluble in water, do not conduct electricity and are highly volatile. The molecular lattice is formed by ice, solid carbon dioxide(“dry ice”), solid hydrogen halides, solid simple substances formed by one- (noble gases), two- (F 2, Cl 2, Br 2, J 2, H 2, N 2, O 2), three- ( O 3), four- (P 4), eight- (S 8) atomic molecules, many crystalline organic compounds. |
| Metal | Consist of metal atoms or ions joined by metallic bonds. The nodes of metal lattices are occupied by positive ions, between which valence electrons, which are in a free state (electron gas), move. The metal grill is durable. This explains the hardness, low volatility, and heat melting and boiling. It also determines such characteristic properties of metals as electrical and thermal conductivity, shine, malleability, plasticity, opacity, and photoelectric effect. Pure metals and alloys have a metallic crystal lattice. |
Crystals are divided into three classes based on electrical conductivity:
Conductors of the first kind– electrical conductivity 10 4 - 10 6 (Ohm×cm) -1 – substances with a metal crystal lattice, characterized by the presence of “current carriers” - freely moving electrons (metals, alloys).
Dielectrics (insulators)– electrical conductivity 10 -10 -10 -22 (Ohm×cm) -1 – substances with an atomic, molecular and less often ionic lattice, which have high binding energy between particles (diamond, mica, organic polymers, etc.).
Semiconductors – electrical conductivity 10 4 -10 -10 (Ohm×cm) -1 – substances with an atomic or ionic crystal lattice that have weaker binding energy between particles than insulators. With increasing temperature, the electrical conductivity of semiconductors increases (gray tin, boron, silicon, etc.)
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Theoretical information
Chemistry is natural Science about substances, their structure, properties and mutual transformations. The most important task of chemistry is to obtain substances and materials with the necessary for various specific
Chemical properties of oxides
Basic Amphoteric Acidic Reacts with excess acid to form salt and water. Basic oxides correspond to basic
Obtaining acids
Oxygen-containing 1. Acid oxide + water 2. Non-metal + strong oxidizing agent
Chemical properties of acids
Oxygen-containing Oxygen-free 1. Change the color of the indicator litmus-red, methyl orange-pink
Obtaining salts
1. Using metals Medium (normal) metal + non-metal metal salts (st.
Chemical properties of medium salts
Decomposition on ignition Salt + metal Salt + salt
Relationship between salts
From medium salts it is possible to obtain acidic and basic salts, but the reverse process is also possible. Acid salts
NOMENCLATURE OF INORGANIC COMPOUNDS
Chemical nomenclature- a set of rules that allow you to unambiguously compose this or that formula or the name of any chemical substance, knowing its composition and structure.
Numeric prefixes
Multiplier Set-top box Multiplier Set-top box Multiplier Set-top box mono
Systematic and trivial names of some substances
Formula Systematic name Trivial name Sodium chloride Table salt
Element names and symbols
The symbols of chemical elements according to IUPAC rules are given in the periodic table by D.I. Mendeleev. The names of chemical elements in most cases have Latin roots. In case
Formulas and names of complex substances
Just as in the formula of a binary compound, in the formula of a complex substance the symbol of a cation or atom with a partial positive charge is in first place, and in the second place is the symbol of an anion or atom with a partial positive charge.
Systematic and international names of some complex substances
Formula Systematic name International name tetraoxosulfate(VI) sodium(I) sulfate
Names of the most common acids and their anions
Acid Anion (acid residue) Formula Name Formula Name &nb
Grounds
According to international nomenclature The names of the bases are made up of the word hydroxide and the name of the metal. For example, - sodium hydroxide, - potassium hydroxide, - calcium hydroxide. If
Medium salts of oxygen-containing acids
The names of the middle salts consist of the traditional names of cations and anions. If an element exhibits one oxidation state in the oxoanions it forms, then the name of the anion ends in -at
Acid and basic salts
If the salt contains hydrogen atoms, which upon dissociation exhibit acidic properties and can be replaced by metal cations, then such salts are called acidic. Titles
BASIC CONCEPTS AND LAWS OF CHEMISTRY
Atomic-molecular theory of the structure of matter M.V. Lomonosov is one of the foundations of scientific chemistry. Universal recognition atomic-molecular theory received at the beginning of the 19th century. Pos
Chemical element. Atomic and molecular mass. Mole
An atom is the smallest particle of a chemical element that retains all its chemical properties. An element is a type of atom with the same charge i
The number of particles in 1 mole of any substance is the same and equals 6.02 × 1023. This number is called Avogadro's number and is denoted
The number of moles of a substance (nx) is physical quantity, proportional to the number of structural units of this substance. (1) where, is the number of hours
Basic stoichiometric laws
The law of conservation of mass (M.V. Lomonosov, 1748; A.L. Lavoisier 1780) serves as the basis for calculating the material balance of chemical processes): the mass of substances that have entered into chemical
Equivalent. Law of equivalents
Equivalent (E) is a real conditional particle of a substance that can attach, replace, release or be in any other way e
Solution.
Example 4. Calculate the molar mass of sulfur equivalents in the compounds. Solution
Theoretical information
A solution is a homogeneous thermodynamically stable system consisting of a solute, a solvent and the products of their interaction. A component whose physical state is not
Theoretical information
The chemical process can be considered as the first step in the ascent from chemical objects - electron, proton, atom - to a living system. The study of chemical processes is an area
Standard thermodynamic functions
Substance Δ H0298, kJ/mol Δ G0298, kJ/mol S0
Theoretical information
Kinetics of chemical reactions is the study of chemical processes, the laws of their occurrence in time, speeds and mechanisms. Associated with studies of the kinetics of chemical reactions
The effect of temperature on the reaction rate.
With an increase in temperature for every 10 0, the rate of most chemical reactions increases by 2-4 times, and, conversely, with a decrease in temperature, it decreases accordingly by as much
The influence of the catalyst on the reaction rate.
One way to increase the rate of a reaction is to lower the energy barrier, that is, decrease. This is achieved by introducing catalysts. Catalyst - substance
CHEMICAL EQUILIBRIUM
There are reversible and irreversible reactions. Irreversible reactions are called those, after the occurrence of which, the system and the external environment at the same time cannot be returned to their previous state. They're coming
Theoretical information
The chemical properties of any element are determined by the structure of its atom. From a historical point of view, the theory of atomic structure was consistently developed by: E. Rutherford, N. Bohr, L. de Broglie, E.
Basic characteristics of proton, neutron and electron
Particle Symbol Rest mass Charge, C kg a.m.u. proton p
Particle-wave properties of particles
The characterization of the state of electrons in an atom is based on the position of quantum mechanics about the dual nature of the electron, which simultaneously has the properties of a particle and a wave. For the first time in duality
Number of sublevels in energy levels
Principal quantum number n Orbital number l Number of sublevels Sublevel designation
Number of orbitals at energy sublevels
Orbital quantum number Magnetic quantum number Number of orbitals with a given value l l
Sequence of filling atomic orbitals
The population of atomic orbitals (AO) by electrons is carried out according to the principle of least energy, the Pauli principle and Hund’s rule, and for multi-electron atoms - the Klechkovsky rule.
Electronic formulas of elements
A record reflecting the distribution of electrons in an atom of a chemical element across energy levels and sublevels is called the electronic configuration of this atom. Mostly (impossible)
Periodicity of atomic characteristics
Periodic nature of change chemical properties atoms of elements depends on changes in the radius of the atom and ion. The radius of a free atom is taken to be the position of the main
Ionization potentials (energies) I1, eV
Groups of elements I II III IV V VI VII VI
Ionization potentials (energies) I1, eV of group V elements
p-elements As 9.81 d-elements V 6.74 Sb 8.64 Nb 6.88 Bi 7.29
The energy value (Eav) of electron affinity for some atoms.
Elem. H He Li Be B C N O F
Relative electronegativity of elements
H 2.1 Li 1.0 Be 1.5 B 2.0
Dependence of the acid-base properties of oxides on the position of the element in the periodic system and its oxidation state.
From left to right across the period, the elements weaken their metallic properties and strengthen their non-metallic ones. The basic properties of the oxides are weakened, and the acidic properties of the oxides are enhanced.
The nature of the change in the properties of bases depending on the position of the metal in the periodic table and its degree of oxidation.
Over the period, from left to right, a gradual weakening of the basic properties of hydroxides is observed. For example, Mg(OH)2 is a weaker base than NaOH, but a stronger base than Al(OH)3
The dependence of the strength of acids on the position of the element in the periodic table and its oxidation state.
According to the period for oxygen-containing acids, the strength of the acids increases from left to right. Thus, H3PO4 is stronger than H2SiO3; in turn, H2SO
Properties of substances in different states of aggregation
State Properties Gaseous 1. Ability to take on the volume and shape of a vessel. 2. Compressibility. 3. Bys
Comparative characteristics of amorphous and crystalline substances
Substance Characteristics Amorphous 1. Short-range order of particle arrangement. 2. Isotropy of physical properties
In the Periodic System D.I. Mendeleev
1. Indicate the name of the element and its designation. Determine the element's serial number, period number, group, subgroup. Specify physical meaning system parameters – serial number, period numbers
Theoretical information
All chemical reactions are essentially donor-acceptor and differ in the nature of the particles that are exchanged: electron donor-acceptor and proton donor-acceptor. Chemical reactions
Characteristics of elements and their connections in OVR
Typical reducing agents 1. neutral metal atoms: Me0 – nē → Mep+ 2. hydrogen and non-metals of groups IV-VI: carbon, phosphorus,
Types of OVR
Intermolecular reactions that occur with a change in the oxidation state of atoms in various molecules. Mg + O2 = 2MgO Intramo
Drawing up equations for redox reactions
1. electron balance method (scheme) 1. Write the equation in molecular form: Na2SO3 + KMnO4 + H2SO4 → MnSO
Participation of ions in various environments
Medium The product has more oxygen atoms The product has fewer oxygen atoms Acidic Ion + H2O U
Standard electrode potentials of metals
It allows us to draw a number of conclusions regarding the chemical properties of elements: 1. each element is capable of reducing all ions of greater importance from salt solutions
Initial data
Option Reaction equation K2Cr2O7 + KI + H2SO4 → Cr2
Theoretical information
Many ions are capable of attaching molecules or opposing ions to themselves and turning into more complex ions, called complex ions. Complex connections (CS) are connections in a node
Structure of complex compounds
In 1893, A. Werner formulated the principles that laid the foundation for the coordination theory. Coordination principle: the coordinating atom or ion (Men+) is surrounded by opposite
Main complexing agents in CS
Complexing agent Ion charge Examples of complexes Metal n+ HCl ®++Cl- - primary dissociation
Equilibrium in a solution always shifts to the side where the less soluble substance or weaker electrolyte is located.
Cl + HNO3 → AgCl↓ + NH4NO3 КН=6.8·10-8 PR =1.8·10-10 Since PR<
The nature of chemical bonds in complex compounds
The first theory explaining the formation of CS was the theory of ionic (heteropolar) bonding. Kossel and A. Magnus: a multiply charged ion – complexing agent (d-element) has a strong
Weak field
The action of ligands causes splitting of the d-sublevel: dz2, dx2-y2 – high-spin doublet (d¡)
Geometric structure of CS and type of hybridization
K.ch. Type of hybridization Geometric structure Example sp Linear n∙m (76) Nernst’s rule.PR - in saturated ra
Theoretical information
Water is a weak electrolyte. It is polar and occurs in the form of hydrated clusters. Due to thermal movement, the bond is broken and interaction occurs: H2O↔[
Change in color of some indicators
Indicator Color transition area pH Color change Phenolphthalein 8.2-10 Bes
Henderson–Hasselbach equations
for type 1 buffer systems (weak acid and its anion): pH = pKa + log([proton acceptor]/[proton donor])
HYDROLYSIS.
Hydrolysis underlies many processes in the chemical industry. Hydrolysis of wood is carried out on a large scale. The hydrolysis industry produces from non-food raw materials (wood,
Mechanism of hydrolysis by anion.
1. Anions with a high polarizing effect: sulfide, carbonate, acetate, sulfite, phosphate, cyanide, silicate - anions of weak acids. They do not have a vacant orbital, an excess father is working
Scope of the academic discipline “General and Inorganic Chemistry” and types of academic work for full-time students of the Faculty of Pharmacy
Type of academic work Total hours/credit units Semester I hours Classroom hours
Laboratory classes in general and inorganic chemistry for full-time students of the Faculty of Pharmacy
I semester (duration - 5 hours) Lesson number Section 1 General chemistry Module 1 B
Lectures on general and inorganic chemistry for full-time students of the Faculty of Pharmacy
I semester (duration - 2 hours) No. Lecture topic Subject, tasks, methods and laws of chemistry
Names of the most important acids and salts.
Acid Names of acid salt HAlO2 meta-aluminum m
Values of some fundamental physical constants
Constant Designation Numerical value Speed of light in vacuum Planck's constant Elementary electric charge
Thermodynamic properties of substances.
Substance ΔH0298, kJ/mol ΔS0298, J/(mol K) ΔG0
Standard electrode potentials (E0) of some systems
