They have the same type of crystal lattices. Crystal lattices

Chemistry is an amazing science. So much incredible can be found in seemingly ordinary things.

Everything material that surrounds us everywhere exists in several states of aggregation: gases, liquids and solids. Scientists have also isolated the 4th - plasma. At a certain temperature, a substance can change from one state to another. For example, water: when heated above 100, from a liquid form, it turns into steam. At temperatures below 0, it passes into the next aggregate structure - ice.

Whole material world has in its composition a mass of identical particles that are interconnected. These smallest elements are strictly arranged in space and form the so-called spatial framework.

Definition

A crystal lattice is a special structure of a solid substance, in which the particles are in a geometrically strict order in space. It is possible to detect nodes in it - places where elements are located: atoms, ions and molecules and internodal space.

Solids, depending on the range of high and low temperatures, are crystalline or amorphous - they are characterized by the absence of a specific melting point. When exposed to elevated temperatures, they soften and gradually turn into a liquid form. Such substances include: resin, plasticine.

In this regard, it can be divided into several types:

• atomic;
• ionic;
• molecular;
• metal.

But at different temperatures, one substance can have various forms and exhibit a variety of properties. This phenomenon is called allotropic modification.

Atomic type

In this type, atoms of one or another substance are located at the nodes, which are connected by covalent bonds. This type of bond is formed by a pair of electrons of two neighboring atoms. Due to this, they are connected evenly and in a strict order.

Substances with an atomic crystal lattice are characterized by the following properties: strength and high melting point. This type of bond is present in diamond, silicon and boron..

Ionic type

Oppositely charged ions are located at the nodes that create an electromagnetic field that characterizes physical properties substances. These will include: electrical conductivity, refractoriness, density and hardness. Table salt and potassium nitrate are characterized by the presence of an ionic crystal lattice.

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Molecular type

In sites of this type, there are ions bound together by van der Waals forces. Due to weak intermolecular bonds, such substances, for example, ice, carbon dioxide and paraffin, are characterized by plasticity, electrical and thermal conductivity.

metal type

In its structure, it resembles a molecular one, but it still has stronger bonds. The difference of this type is that positively charged cations are located at its nodes. The electrons that are in the interstitial space, participate in the formation of an electric field. They are also called electric gas.

Simple metals and alloys are characterized by a metallic lattice type. They are characterized by the presence of metallic luster, plasticity, thermal and electrical conductivity. They can melt at different temperatures.

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Lesson type: Combined.

The purpose of the lesson: To create conditions for the formation of students' ability to establish a causal dependence of the physical properties of substances on the type of chemical bond and type of crystal lattice, to predict the type of crystal lattice based on the physical properties of a substance.

Lesson objectives:

• To form concepts of the crystalline and amorphous state of solids, to acquaint 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 the properties of matter .
• Continue the formation of students' worldview, consider the mutual influence of the components of the whole-structural particles of substances, as a result of which new properties appear, develop the ability to organize their own educational work, follow the rules of working in a team.
• Develop cognitive interest schoolchildren, using problem situations;

Equipment: Periodic system of D.I. Mendeleev, collection "Metals", non-metals: sulfur, graphite, red phosphorus, crystalline silicon, iodine; Presentation "Types of crystal lattices", models of crystal lattices different types(salt, diamond and graphite, carbon dioxide and iodine, metals), samples of plastics and products from them, glass, plasticine, computer, projector.

During the classes

1. Organizational moment.

The teacher greets the students, fixes the absent ones.

2. Checking knowledge on topics” Chemical bond. The degree of oxidation”.

Independent work(15 minutes)

3. Learning new material.

The teacher announces the topic of the lesson and the purpose of the lesson. (Slide 1,2)

Students write the date and topic of the lesson in their notebooks.

Knowledge update.

The teacher asks the class questions:

1. What types of particles do you know? Do ions, atoms and molecules have charges?
2. What types of chemical bonds do you know?
3. What are the states of aggregation of substances?

Teacher:“Any substance can be gas, liquid and solid. For example, water. Under normal conditions, it is a liquid, but it can be steam and ice. Or oxygen under normal conditions is a gas, at a temperature of -1940 C it turns into a liquid blue color, and at a temperature of -218.8 ° C it hardens into a snow-like mass consisting of crystals of blue color. In this lesson, we will consider the solid state of substances: amorphous and crystalline. (Slide 3)

Teacher: amorphous substances do not have a clear melting point - when heated, they gradually soften and become fluid. Amorphous substances include, for example, chocolate, which melts both in the hands and in the mouth; chewing gum, plasticine, wax, plastics (examples of such substances are shown). (Slide 7)

Crystalline substances have a clear melting point and, most importantly, are characterized by the correct arrangement of particles at strictly defined points in space. (Slides 5,6) When these points are connected by straight lines, a spatial frame is formed, called a crystal lattice. The points at which crystal particles are located are called lattice nodes.

Students write down the definition in a notebook: “A crystal lattice is a set of points in space in which the particles that form a crystal are located. The points where the particles of the crystal are located are called the nodes of the lattice.

Depending on what types of particles are in the nodes of this lattice, there are 4 types of lattices. (Slide 8) If there are ions in the nodes of the crystal lattice, then such a lattice is called ionic.

The teacher asks students questions:

- What will be called crystal lattices, in the nodes of which there are atoms, molecules?

But there are crystal lattices, in the nodes of which there are both atoms and ions. Such gratings are called metal.

Now we will fill in the table: "Crystal lattices, type of bond and properties of substances." In the course of filling in the table, we will establish the relationship between the type of lattice, the type of connection between particles and the physical properties of solids.

Consider the 1st type of crystal lattice, which is called ionic. (Slide 9)

What is the chemical bond in these substances?

Look at the ionic crystal lattice (a model of such a lattice is shown). At its nodes are positively and negatively charged ions. For example, a sodium chloride crystal is made up of positive sodium ions and negative chloride ions in a cube-shaped lattice. Substances with an ionic crystal lattice include salts, oxides and hydroxides of typical metals. Substances with an ionic crystal lattice have high hardness and strength, they are refractory and non-volatile.

Teacher: The physical properties of substances with an atomic crystal lattice are the same as those of substances with an ionic crystal lattice, but often in superlatives- very hard, very durable. Diamond, in which the atomic crystal lattice is the hardest substance of all natural substances. It serves as a standard of hardness, which, according to a 10-point system, is rated with the highest score of 10. (Slide 10). According to this type of crystal lattice, you yourself will make necessary information in the table, having independently worked with the textbook.

Teacher: Let's consider the 3rd type of crystal lattice, which is called metallic. (Slides 11,12) At the nodes of such a lattice there are atoms and ions, between which electrons move freely, binding them into a single whole.

Such internal structure metals and determines their characteristic physical properties.

Teacher: What physical properties of metals do you know? (ductility, plasticity, electrical and thermal conductivity, metallic luster).

Teacher: What groups are all substances divided into by structure? (Slide 12)

Let us consider the type of crystal lattice, which is possessed by such well-known substances as water, carbon dioxide, oxygen, nitrogen and others. It's called molecular. (Slide 14)

What particles are located at the nodes of this lattice?

The chemical bond in the molecules that are at the lattice sites can be both covalent polar and covalent non-polar. Despite the fact that the atoms within the molecule are bound by very strong covalent bonds, weak forces of intermolecular attraction act between the molecules themselves. Therefore, substances with a molecular crystal lattice have low hardness, low melting points and are volatile. When gaseous or liquid substances special conditions turn into solid, then they have a molecular crystal lattice. Examples of such substances can be solid water - ice, solid carbon dioxide - dry ice. Such a lattice has naphthalene, which is used to protect woolen products from moths.

– What properties of the molecular crystal lattice determine the use of naphthalene? (volatility). As you can see, the molecular crystal lattice can have not only solid simple substances: noble gases, H 2, O 2, N 2, I 2, O 3, white phosphorus P 4, but and complex: solid water, solid hydrogen chloride and hydrogen sulfide. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).

The lattice sites contain non-polar or polar molecules. Despite the fact that the atoms inside the molecules are bound by strong covalent bonds, weak forces of intermolecular interaction act between the molecules themselves.

Conclusion: Substances are fragile, have low hardness, low temperature melting, flying.

Question: What process is called sublimation or sublimation?

Answer: The transition of a substance from a solid state of aggregation immediately to a gaseous state, bypassing the liquid state, is called sublimation or sublimation.

Demonstration of experience: iodine sublimation

Then the students take turns naming the information that they wrote down in the table.

Crystal lattices, type of bond and properties of substances.

Lattice type	Types of particles at lattice sites	Communication type between particles	Substance examples	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 electricity
Atomic	atoms	1. Covalent non-polar - 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 (IV) - SiO 2	Very hard, very refractory, strong, non-volatile, insoluble in water
Molecular	molecules	Between molecules - weak forces intermolecular attraction, but inside molecules - a strong covalent bond	Solids under special conditions, which 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 a small hardness
metal	atom ions	Metal - different strength	Metals and alloys	Malleable, have gloss, ductility, heat and electrical conduction

Teacher: What can we conclude from the work done on the table?

Conclusion 1: The physical properties of substances depend on the type of crystal lattice. Composition of a substance → Type of chemical bond → Type of crystal lattice → Properties of substances . (Slide 18).

Question: Which type of crystal lattice from the above is not found in simple substances Oh?

Answer: Ionic crystal lattices.

Question: What crystal lattices are typical for simple substances?

Answer: For simple substances - metals - metallic crystal cell; for non-metals - atomic or molecular.

Work with the Periodic system of D.I. Mendeleev.

Question: Where are the metal elements in the Periodic Table and why? Elements are non-metals and why?

Answer : If we draw a diagonal from boron to astatine, then in the lower left corner from 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 for 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 contain from four to eight electrons. These are elements IV A, V A, VI A, VII A, VIII A and boron.

Teacher: Let's find non-metal elements in which 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 the Periodic system of D.I. Mendeleev.

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 lattice type is metallic.

For non-metal elements IV A and boron in a simple substance, the crystal lattice is atomic; and the elements V A, VI A, VII A, VIII A in simple substances have a molecular crystal lattice.

We continue to work with the completed table.

Teacher: Look closely at the table. What pattern is observed?

We carefully listen to the answers of the students, after which we draw a conclusion together with the class. Conclusion 2 (slide 17)

4. Fixing the material.

Test (self-control):

Substances that have a molecular crystal lattice, as a rule:
a) Refractory and highly soluble in water
b) Fusible and volatile
c) Solid and electrically conductive
d) Thermally conductive and plastic

The concept of "molecule" is not applicable in relation to the structural unit of a substance:
a) Water
b) Oxygen
c) Diamond
d) Ozone

The atomic crystal lattice is characteristic for:
a) Aluminum and graphite
b) Sulfur and iodine
c) Silicon oxide and sodium chloride
d) Diamond and boron

If a substance is highly soluble in water, has a high melting point, and is electrically conductive, then its crystal lattice:
a) Molecular
b) Nuclear
c) Ionic
d) metal

5. Reflection.

6. Homework.

Describe each type of crystal lattice according to the plan: What is in the nodes of the crystal lattice, structural unit → Type of chemical bond between the particles of the node → Forces of interaction between crystal particles → Physical properties due to the crystal lattice → Aggregate state of matter under normal conditions → Examples.

According to the formulas of the given substances: SiC, CS 2 , NaBr, C 2 H 2 - determine the type of crystal lattice (ionic, molecular) of each compound and, based on this, describe the expected physical properties of each of the four substances.

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 non-volatile.

Substances with an ionic crystal lattice have the following properties:

1. Relatively high hardness and strength;

2. Fragility;

3. Heat resistant;

4. Refractoriness;

5. Non-volatile.

Examples: salts - sodium chloride, potassium carbonate, bases - calcium hydroxide, sodium hydroxide.

4. The mechanism of formation of a covalent bond (exchange and donor-acceptor).

Each atom tends to complete its outer electronic level in order 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 are superimposed.

Demonstration of an application and a scheme for the formation of a covalent non-polar chemical bond in a hydrogen molecule. (Students write and draw diagrams).

Conclusion: The bond between atoms in a hydrogen molecule is carried out through a common electron pair. Such a bond is called a covalent bond.

What bond is called covalent non-polar? (Textbook p. 33).

Drawing up electronic formulas of molecules of simple substances of non-metals:

CI CI is the electronic formula of the chlorine molecule,

CI -- CI is the structural formula of the chlorine molecule.

N N is the electronic formula of the nitrogen molecule,

N ≡ N - structural formula of the nitrogen molecule.

Electronegativity. Covalent polar and non-polar bonds. Multiplicity of a covalent bond.

But molecules can also form different atoms of non-metals, in which case the common electron pair will shift to a more electronegative chemical element.

Study the textbook material on page 34

Conclusion: Metals have a lower electronegativity value than non-metals. And it's very different between them.

Demonstration of a scheme for the formation of a polar covalent bond in a hydrogen chloride molecule.

The shared electron pair is biased towards chlorine, which is more electronegative. So this is a covalent bond. It is formed by atoms whose electronegativity does not differ much, so it is a covalent polar bond.

Compilation of electronic formulas of hydrogen iodine and water molecules:

H J - electronic formula of the hydrogen iodine molecule,

H → J is the structural formula of the hydrogen iodide molecule.

HO is the electronic formula of the water molecule,

H → O - structural formula of the water molecule.

Independent work with the textbook: write out 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

An atom of which chemical element has a nuclear charge of +11

- Write down the scheme of the electronic structure of the sodium atom

– Is the outer layer complete?

– How to complete the filling of the electron layer?

- Draw a diagram of the recoil of an electron

– Compare the structure of the sodium atom and ion

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 scheme of the electronic structure of the atom.

– Layer completed? How to achieve this.

– Make a diagram of the completion of the electron layer of chlorine.

Group task:

1-3 group: Compose the electronic and structural formulas of the molecules of substances and indicate the type of bond Br 2; NH3.

4-6 groups: Compose the 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 self-examination.

Oral survey.

1. Define the term "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 ways of completing the outer electron layer, characteristic of atoms of metals and nonmetals, differ? What are the reasons for this?

7. What chemical elements are able to donate electrons, accept electrons?

What happens between atoms when they donate and accept electrons?

What is the name of the particles formed from an atom as a result of the donation or addition of electrons?

8. What will happen when the atoms of a metal and a non-metal meet?

9. How is an ionic bond formed?

10. A chemical bond formed due to the formation of common electron pairs is called ...

11. Covalent bond happens ... and ...

12. What is the similarity of a covalent polar and covalent non-polar bond? What determines the polarity of a bond?

13. What is the difference between covalent polar and covalent non-polar bonds?

LESSON PLAN #8

Discipline: Chemistry.

Subject: Metal connection. Aggregate states of substances and hydrogen bonding .

Purpose of the lesson: To form the concept of chemical bonds using the example of a metallic bond. Achieve an understanding of the mechanism of bond formation.

Planned results

Subject: formation of a person's outlook and functional literacy for solving practical problems; ability to process, explain the results; willingness and ability to apply methods of knowledge 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 in the professional field;

Personal: the ability to use the achievements of modern chemical science and chemical technology to increase one's own intellectual development in the chosen professional activity;

Time norm: 2 hours

Class type: Lecture.

Lesson plan:

1. Metal connection. Metallic crystal lattice and metallic 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 system chemical elements, crystal lattice, handout.

Literature:

1. Chemistry grade 11: textbook. for general education organizations G.E. Rudzitis, F.G. Feldman. - M.: Enlightenment, 2014. -208 p.: Ill..

2. Chemistry for professions and specialties of a technical profile: a textbook for students. medium institutions. prof. education / O.S.Gabrielyan, I.G. Ostroumov. - 5th ed., erased. - M .: Publishing Center "Academy", 2017. - 272 pp., with color. ill.

Lecturer: Tubaltseva Yu.N.

Let's talk about solids. Solids can be divided into two large groups: amorphous And crystalline. We will separate them according to the principle whether there is order or not.

IN amorphous substances molecules are arranged randomly. There are no regularities in their spatial arrangement. In fact, amorphous substances are very viscous liquids, so viscous that they are solid.

Hence the name: “a-” is a negative particle, “morphe” is a form. Amorphous substances include: glasses, resins, wax, paraffin, soap.

The lack of order in the arrangement of particles determines the physical properties of amorphous bodies: they do not have fixed melting points. As they heat up, their viscosity gradually decreases, and they also gradually become liquid.

In contrast to amorphous substances, there are crystalline ones. Particles of a crystalline substance are spatially ordered. This is the 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 which particles are in lattice nodes, and from what bonds hold them distinguish: molecular, nuclear, ionic And metal gratings.

Why is it fundamentally important to know what the crystal lattice of a substance is? What does she define? All. Structure defines how chemical and physical properties of matter.

The simplest example is 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. It's all determined by structure: the order in which these nucleotides are arranged.

Molecular crystal lattice.

A typical example is water in the solid state (ice). The lattice sites contain whole molecules. And hold them together intermolecular interactions: hydrogen bonds, van der Waals forces.

These connections are weak, so molecular lattice – the most fragile, the melting point of such substances is low.

A good diagnostic sign: if a substance has a liquid or gaseous state under normal conditions 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 hold 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.

The molecular crystal lattice has:

1. Some simple substances of non-metals: I 2, P, S (that is, all non-metals that do not have an atomic lattice).
2. Almost all organic matter ( except for salts).
3. And as mentioned earlier, substances under normal conditions are liquid or gaseous (being frozen) and / or having an odor (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 covalent bonds hold the lattice (after all, they bind neutral atoms).

A classic example is the standard of hardness strength - diamond (by chemical nature, it is a simple substance carbon). Connections: covalent non-polar, since only carbon atoms form the lattice.

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:

1. strength, hardness
2. high melting points (refractory)
3. non-volatile substances
4. insoluble (neither in water nor in other solvents)

All these properties are due to the strength of covalent bonds.

There are few substances in the atomic crystal lattice. There is no special pattern, so you just need to remember them:

1. Allotropic modifications of carbon (C): diamond, graphite.
2. Boron (B), silicon (Si), germanium (Ge).
3. Only two allotropic modifications of phosphorus have an atomic crystal lattice: red phosphorus and black phosphorus. (White phosphorus has a molecular crystal lattice).
4. SiC - carborundum (silicon carbide).
5. BN is boron nitride.
6. Silica, rock crystal, quartz, river sand - all these substances have the composition SiO 2.
7. 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 electric current, and diamond is transparent, does not stain and does not conduct current. They differ in structure.

And then, and then - the atomic lattice, but different. Therefore, the properties are different.

Ionic crystal lattice.

A classic example: table salt: NaCl. At the nodes of the lattice are individual ions: Na+ and Cl–. Holds the lattice electrostatic forces of attraction between ions ("plus" is attracted to "minus"), that is ionic bond.

Ionic crystal lattices are quite strong, but brittle, the melting points of such substances are quite high (higher than that of representatives of a metal one, but lower than that of substances with an atomic lattice). Many are water soluble.

As a rule, there are no problems with the definition of 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).

Metallic crystal lattice.

The metal grating is realized in simple substances metals. Earlier we said that all the splendor of the metallic bond can only be understood together with the metallic crystal lattice. The hour has come.

The main property of metals: electrons on outer energy level poorly held, so they are easily given. 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 recoil and electron attachment are constantly taking place: an electron is detached 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 the metal crystal lattice contain both neutral atoms and metal cations. And free electrons travel between nodes:

These free electrons are called electron gas. It is they that determine the physical properties of simple substances of metals:

1. thermal and electrical conductivity
2. metallic luster
3. malleability, plasticity

This is a metallic bond: metal cations are attracted to neutral atoms and all this is “glued together” by free electrons.

How to determine the type of crystal lattice.

P.S. There is something in school curriculum and the USE program on this topic is something with which we do not quite agree. Namely: a generalization that any metal-nonmetal bond is an ionic bond. This assumption is deliberately made, apparently to simplify the program. But this leads to distortion. The boundary between ionic and covalent bonds is conditional. Each bond has its own percentage of "ionic" and "covalent". The bond with a low-active metal has a small percentage of "ionicity", it is more like a covalent one. But according to the USE program, it is "rounded" towards the ionic one. It 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 in this way. But according to the "metal-non-metal" standard, we qualify this bond as ionic. And it turns out a contradiction: the lattice is atomic, and the bond is ionic. This is what oversimplification leads to.