Types of crystal lattices chemistry. Atomic crystal lattice

Crystal cell- a system of points located in equal, parallel oriented vertices and parallelepipeds adjacent along the faces without gaps, filling the space of points called nodes, straight lines - rows, planes - grids, parallelepipeds are called elementary cells.

Types of crystal lattices: atomic - if atoms are located at the nodes, ionic - if ions are located at the nodes, molecular - if molecules are located at the nodes

2. Properties of crystalline substances - homogeneity, anisotropy, ability to self-cut.

Uniformity- two identical elementary volumes of a substance, parallel oriented in space, but isolated at different points of the substance, absolutely identical in properties (beryl - tourmaline).

Anisotropy- in different directions of the crystal lattice in non-parallel directions, many properties (for example, strength, hardness, refractive index) are different.

Ability to self-destruct– the property of crystals, when growing freely, to form regularly faceted polyhedra.

Property of constancy of dihedral nodes– the angles between the corresponding faces and edges in all crystals of the same substance are the same.

3. The concept of syngony. What categories are syngonies divided into?

Syngony is a set of types of symmetries that have 1 or several common symmetry elements, with an equal number of unit directions. The cell is characterized by the relationships between the a, b, and c axes and the cell angles.

There are 7 Divided into:

Lowest( do not have symmetry axes higher than the second order)

Average ( they have one axis of symmetry of higher order)

Single directions– directions that are not repeated in crystals.

Being the largest classification division in the symmetry of crystals, each symmetry group includes several point groups of symmetries and Bravais lattices.

4.Simple shapes and combinations. The physical meaning of isolating simple forms in a crystal.

According to their appearance, crystals are divided into simple shapes and combinations. Simple forms– crystals obtained from one face by the action of an element of symmetry on it.

Elements of symmetry:

geometric image

plane of symmetry- a plane perpendicular to the image, dividing the figure into 2 parts, corresponding as an object and its mirror image.

Axis of symmetry- this is a straight line perpendicular to the image, when rotated around 360 o the figure is aligned with itself n times.

Center of symmetry- a point inside a crystal characterized by the fact that each straight line drawn through it meets identical points on both sides at equal distances.

Combinations- crystals consisting of faces of various types, differing in shape and size. Formed by a combination of two or more simple forms. There are as many types of faces on a uniformly developed crystal as there are simple forms in it.

Selecting faces of different types has physical meaning , since different faces grow at different rates and have different properties (hardness, density, refractive index).

Simple forms are open and closed. A closed simple form, with the help of faces of the same type, independently closes the space (tetragonal dipyramid), an open simple form can close the space only in combination with other simple forms (tetragonal pyramid + plane.) There are 47 simple forms in total. All of them are divided into categories:

Monohedron is a simple shape represented by one face.

Pinacoid - two equal parallel faces that can be reversed.

Dihedron - two equal intersecting faces (can intersect on their continuation).

Rhombic prism - four equal pairs of parallel faces; in cross-section they form a rhombus.

A rhombic pyramid has four equal intersecting sides; in cross-section they also form a rhombus. The listed simple forms are open, since they do not close the space. The presence in a crystal of open simple forms, for example, a rhombic prism, necessarily causes the presence of other simple forms, for example, a pinacoid or a rhombic bipyramid, necessary to obtain a closed form.

Of the closed simple forms of lower systems, we note the following. Rhombic dipyramid: two rhombic pyramids joined at their bases; the shape has eight different faces, giving a rhombus in cross section; A rhombic tetrahedron has four faces that enclose the space and have the shape of oblique triangles.

Middle category(systems: triclinic, tetragonal, hexagonal) – 27 p.f.: monohedron, pinocoid, 6 dipyramids, 6 pyramids, 6 prisms, tetrahedron, rhombohedron, 3 trapezohedrons (trapezoid-shaped faces), 2 scalenoids (formed by doubling the faces of a tetrahedron and rhombohedron).

Highest category– 15 p.f.: the main ones are tetrahedron, octahedron, cube. If instead of one face there are 3 faces - a tritetrahedron, if 6 - a hexatetrahedron, if 4 - a tetratetrahedron. The faces can be 3x, 4x, 5x: 3x - trigon, 4x - tetragon, 5x - pentagon.

A simple crystal form is a family of faces interconnected by symmetrical operations. of this class symmetry. All faces that form one simple crystal shape must be equal in size and shape. A crystal may contain one or more simple forms. The combination of several simple forms is called a combination.

Closed forms are those whose edges completely enclose the space enclosed between them, such as a cube;

Open simple forms do not enclose space and cannot exist independently, but only in combinations. For example, prism + pinacoid.

Monohedron (from the Greek “mono” - one, “hedron” - face) - a simple shape represented by one single face. A monohedron is, for example, the base of a pyramid.

 Pinacoid (from the Greek “pinax” - board) is a simple shape consisting of two equal parallel faces, often reversely oriented.

Dihedron (from the Greek "di" - two, "hedron" - face) - a simple shape formed by two equal intersecting (sometimes on their continuation) edges, forming a "straight roof".

Rhombic prism is a simple shape that consists of four equal, pairwise parallel faces, which in cross-section form a rhombus.

Rhombic pyramid - a simple shape consisting of four equal intersecting faces; in cross-section it is also a rhombus. Of the closed simple forms of lower systems, we note the following:

Rhombic dipyramid: two rhombic pyramids joined at their bases. The shape has eight equal faces, giving a rhombus in cross section.

The rhombic tetrahedron is a simple shape, the four faces of which are shaped like oblique triangles and enclose the space.

 Trigonal prism (from the Greek "gon" - angle) - three equal faces intersecting along parallel edges and forming an equilateral triangle in cross-section;

 Tetragonal prism (from the Greek “tetra” - four) - four equal pairs of parallel faces, forming a square in cross-section;

Hexagonal prism (from the Greek "hexa" - six) - six equal faces intersecting along parallel edges and forming a regular hexagon in cross-section.

The names ditrigonal, ditetragonal and dihexagonal are given to prisms with double the number of faces, when all the faces are equal, and the same angles between the faces alternate every other.

Pyramids - simple forms of crystals of the middle category can be, like prisms, trigonal (and ditrigonal), tetragonal (and ditetragonal), hexagonal (and dihexagonal). They form regular polygons in cross-section. The faces of the pyramids are located at an oblique angle to the higher order symmetry axis.

In crystals of the middle category, closed simple forms are also found. There are several such forms:

Dipyramids are simple shapes formed by two equal pyramids joined at their bases. In such forms, the pyramid is doubled by a horizontal plane of symmetry perpendicular to the main axis of symmetry of a higher order (Fig. 8). Dipyramids, like simple pyramids, can have different cross-sectional shapes depending on the order of the axis. They can be trigonal, ditrigonal, tetragonal, ditetragonal, hexagonal and dihexagonal.

Rhombohedron is a simple shape that consists of six diamond-shaped faces and resembles an elongated or diagonally flattened cube. It is only possible in the trigonal system. The upper and lower groups of faces are rotated relative to each other at an angle of 60° so that the lower faces are located symmetrically between the upper ones.

In solids, particles (molecules, atoms and ions) are located so close to each other that the interaction forces between them do not allow them to fly apart. These particles can only perform oscillatory movements around the equilibrium position. Therefore, solids retain their shape and volume.

Based on their molecular structure, solids are divided into crystalline And amorphous .

Structure of crystalline bodies

Crystal cell

Crystalline are those solids, molecules, atoms or ions in which they are arranged in a strictly defined geometric order, forming a structure in space called crystal lattice . This order is periodically repeated in all directions in three-dimensional space. It persists over long distances and is not limited in space. He is called in a long way .

Types of crystal lattices

The crystal lattice is mathematical model, with which you can imagine how particles are located in a crystal. Mentally connecting the points in space where these particles are located with straight lines, we get a crystal lattice.

The distance between atoms located at the sites of this lattice is called lattice parameter .

Depending on which particles are located at the nodes, crystal lattices are molecular, atomic, ionic and metallic .

The properties of crystalline bodies such as melting point, elasticity, and strength depend on the type of crystal lattice.

When the temperature rises to a value at which the melting of a solid begins, the crystal lattice is destroyed. The molecules gain more freedom, and the solid crystalline substance passes into the liquid stage. The stronger the bonds between molecules, the higher the melting point.

Molecular lattice

In molecular lattices, the bonds between molecules are not strong. Therefore, when normal conditions such substances are in liquid or gaseous state. The solid state is possible for them only when low temperatures. Their melting point (transition from solid to liquid) is also low. And under normal conditions they are in a gaseous state. Examples are iodine (I 2), “dry ice” (carbon dioxide CO 2).

Atomic lattice

In substances that have an atomic crystal lattice, the bonds between atoms are strong. Therefore, the substances themselves are very hard. They melt at high temperatures. Crystalline atomic lattice have silicon, germanium, boron, quartz, oxides of some metals and the hardest substance in nature - diamond.

Ionic lattice

Substances with ionic crystal lattice include alkalis, most salts, and oxides of typical metals. Since the attractive force of ions is very strong, these substances can melt only at very high temperatures. They are called refractory. They have high strength and hardness.

Metal grill

At the nodes of the metal lattice, which all metals and their alloys have, both atoms and ions are located. Thanks to this structure, metals have good malleability and ductility, high thermal and electrical conductivity.

Most often, the crystal shape is a regular polyhedron. The faces and edges of such polyhedra always remain constant for a particular substance.

A single crystal is called single crystal . It has a regular geometric shape, a continuous crystal lattice.

Examples of natural single crystals are diamond, ruby, rock crystal, rock salt, Iceland spar, quartz. Under artificial conditions, single crystals are obtained through the process of crystallization, when, by cooling solutions or melts to a certain temperature, a solid substance in the form of crystals is isolated from them. With a slow crystallization rate, the cut of such crystals has natural shape. In this way, under special industrial conditions, single crystals of semiconductors or dielectrics are obtained.

Small crystals randomly fused together are called polycrystals . The clearest example polycrystal - granite stone. All metals are also polycrystalline.

Anisotropy of crystalline bodies

In crystals, particles are located with different densities in different directions. If we connect atoms in one of the directions of the crystal lattice with a straight line, then the distance between them will be the same throughout this direction. In any other direction, the distance between the atoms is also constant, but its value may already differ from the distance in the previous case. This means that interaction forces of different magnitudes act between atoms in different directions. Therefore, the physical properties of the substance in these directions will also differ. This phenomenon is called anisotropy - dependence of the properties of matter on direction.

Electrical conductivity, thermal conductivity, elasticity, refractive index and other properties of a crystalline substance vary depending on the direction in the crystal. Electric current is conducted differently in different directions, the substance is heated differently, and light rays are refracted differently.

In polycrystals the phenomenon of anisotropy is not observed. The properties of the substance remain the same in all directions.

Crystal lattices

8TH GRADE

*According to the textbook: Gabrielyan O.S. Chemistry-8. M.: Bustard, 2003.

Goals. Educational. Give the concept of the crystalline and amorphous state of solids; get acquainted with the types of crystal lattices, their relationship with the types of chemical bonds and the effect on the physical properties of substances; give an idea of ​​the law of constancy of the composition of substances.
Developmental. Develop logical thinking, observation skills and drawing conclusions.
Educational. To form aesthetic taste and collectivism, to broaden one’s horizons.
Equipment and reagents. Models of crystal lattices, filmstrip “Dependence of the properties of substances on composition and structure”, transparencies “Chemical bond. Structure of matter"; plasticine, chewing gum, resins, wax, table salt NaCl, graphite, sugar, water.
Form of work organization. Group.
Methods and techniques. Independent work, demonstration experience, laboratory work.
Epigraph.

DURING THE CLASSES

TEACHER. Crystals are found everywhere. We walk on crystals, build with crystals, create devices and products from crystals, widely use crystals in technology and science, eat crystals, heal with crystals, find crystals in living organisms, go out into the vastness of space roads with the help of devices made of crystals...
What are crystals?
Imagine for a moment that your eyes began to see atoms or molecules; the growth decreased and you were able to enter the crystal. The purpose of our lesson is to understand what the crystalline and amorphous states of solids are, to get acquainted with the types of crystal lattices, and to gain an understanding of the law of constancy of the composition of substances.
What aggregative states of substances are known? Solid, liquid and gaseous. They are interconnected (Scheme 1).

The Tale of Greedy Chlorine

In a certain kingdom, a chemical state, there lived Chlorine. And although he belonged to the ancient family of Halogens, and received a considerable inheritance (he had seven electrons at the external energy level), he was very greedy and envious, and even turned yellow-green from anger. Day and night he was tormented by the desire to become like Argon. He thought and thought and finally came up with: “Argon has eight electrons on the outer level, and I only have seven. So, I need to get one more electron, then I will also be noble.” The next day, Chlorus got ready to go on the road for the treasured electron, but he didn’t have to go far: near the house he met an atom that was like him like two peas in a pod.
“Listen, brother, give me your electron,” Chlorus spoke.
“No, you’d better give me an electron,” answered the twin.
“Okay, then let’s combine our electrons so that no one will be offended,” said the greedy Chlorine, hoping that later he would take the electron for himself.
But that was not the case: both atoms shared the same electrons equally, despite the desperate efforts of the greedy Chlorine to win them over to his side.

TEACHER. Look at the substances on your tables and divide them into two groups. Plasticine, chewing gum, resin, wax are amorphous substances. They often do not have a constant melting point, fluidity is observed, and there is no ordered structure (crystal lattice). On the contrary, salt NaCl , graphite and sugar are crystalline substances. They are characterized by clear melting temperatures, correct geometric shapes, symmetry.
Both amorphous and crystalline substances are used. We will become familiar with the types of crystal lattices and their influence on the physical properties of substances. The creative tasks you have prepared - fairy tales - will help in repeating the types of chemical bonds.

A fairy tale about a polar covalent bond

In a certain kingdom, in a certain state called the “Periodic Table,” there lived a small electron. He had no friends. But one day another electronic device came to him in a village called “External Level”, exactly similar to the first one. They immediately became friends, always walked together and did not even notice how they ended up paired. These electrons are called covalent.

A fairy tale about ionic bonding

Two friends lived in the house of the periodic system of Mendeleev - the metal Na and the non-metal Cl. Each lived in his own apartment: Na - in apartment No. 11, and Cl - at No. 17.
And so the friends decided to join the circle, and there they were told: in order to enter this circle, they must complete the energy level. The friends got upset and trudged home. At home, they thought about how to complete the energy level. And suddenly Cl said:
- Come on, you give me one electron from your third level.
- That is, how will I give it? – Na asked.
- So, take it and give it to me. You will have two levels and all completed, and I will have three levels and also all completed. Then we will be accepted into the circle.
“Okay, take it,” Na said and gave away his electron.
When they came to the circle, the director of the circle asked: “How did you manage to do this?” They told him everything. The director said: “Well done, guys,” and accepted them into his circle. The director gave sodium a card with the sign “+1”, and chlorine – with the sign “-1”. And now he accepts everyone into the circle - metals and non-metals. And what Na and Cl did was what he called an ionic bond.

TEACHER. Do you have a good understanding of the types of chemical bonds? This knowledge will be useful when studying crystal lattices. The world of substances is large and diverse. They have a variety of properties. There are physical and Chemical properties substances. What properties do we classify as physical?
Student answers: state of aggregation, color, density, melting and boiling points, solubility in water, electrical conductivity.

TEACHER. Describe the physical properties of substances: O2, H2O, NaCl, graphite WITH.
Students fill out the table, which as a result takes on the following form.

Table

TEACHER. Based on the physical properties of substances, their structure can be determined.

Transparency.

TEACHER.A crystal is a solid body whose particles (atoms, molecules, ions) are arranged in a certain, periodically repeating order (at nodes). When mentally connecting nodes with lines, a spatial framework is formed - a crystal lattice. There are four types of crystal lattices (Scheme 2, see p. 24 ).

Scheme 2

CRYSTAL LATTICES

TEACHER. What crystal lattices do O 2, H 2 O, NaCl, C ?

Students' answer. O 2 and H 2 O are molecular crystal lattices, NaCl is an ionic lattice,
C – atomic lattice.
Demonstration of crystal lattice models: NaCl, C (graphite), Mg, CO 2.

TEACHER.Pay attention to the types of crystal lattices simple substances depending on their position in the periodic table (p. 79 of the textbook).
What type of lattice is not found in simple substances?
Students' answer. Simple substances do not have ionic lattices.

J.L.Proust (1754–1826)

TEACHER. Substances with a molecular lattice are characterized by the phenomenon of sublimation or sublimation.
Demonstration experience. Sublimation of benzoic acid or naphthalene. (Sublimation is the transformation (when heated) of a solid into a gas, bypassing the liquid phase, and then crystallizing again in the form of frost.)

TEACHER.Substances with a molecular structure obey the law of constancy of the composition of the substance; substances of molecular structure have a constant composition regardless of the method of their preparation. The law was discovered by J.L. Proust. He resolved the long dispute between K.L. Berthollet and J. Dalton in favor of the former.
For example, carbon dioxide or carbon monoxide (IV) CO2 - a complex substance of molecular structure. It consists of two elements: carbon and oxygen, and the molecule contains one carbon atom and two oxygen atoms. Relative molecular mass M r ( CO2 ) = 44, molar mass M( CO2 ) = 44 g/mol. Molar volume V M ( CO2 ) = 22.4 mol (n.s.). Number of molecules in 1 mole of substance N A ( CO2 ) = 6 10 23 molecules.
For substances with an ionic structure, Proust's law is not always satisfied.

Graphic dictation
“Types of chemical bonds and types of crystal lattices”

The signs “+” and “–” indicate whether this statement (1–20) is typical for the type of chemical bond of the specified option.
Option 1. Ionic bond.
Option 2. Covalent nonpolar bond.
Option 3. Covalent polar bond.

Statements.

1. Bonds are formed between metal and non-metal atoms.
2. Bonds are formed between metal atoms.
3. Bonds are formed between non-metal atoms.
4. During the interaction of atoms, ions are formed.
5. The resulting molecules are polarized.
6. Bonding is established by pairing electrons without shifting shared electron pairs.
7. A bond is established by pairing electrons and shifting a common pair to one of the atoms.
8. In progress chemical reaction is happening full transmission valence electrons from one atom of a reacting element to another.
9. The oxidation state of atoms in a molecule is zero.
10. The oxidation states of atoms in a molecule are equal to the number of electrons given or received.
11. The oxidation states of atoms in a molecule are equal to the number of displaced common electron pairs.
12. Compounds with this type of bond form an ionic type crystal lattice.
13. Compounds with this type of chemical bond are characterized by crystalline lattices of the molecular type.
14. Compounds with this type of bond form atomic crystal lattices.
15. Compounds may be gaseous under normal conditions.
16. Compounds are solid under normal conditions.
17. Connections with this type of connection are usually refractory.
18. Substances with this type of bond can be liquid under normal conditions.
19. Substances with such a chemical bond have an odor.
20. Substances with such a chemical bond have a metallic luster.

Answers(self-esteem).

Option 1

Option 2

Option 3

Evaluation criteria: 1–2 errors – “5”, 3–4 errors – “4”, 5–6 errors – “3”.

Fixing the material

Silicon has an atomic crystal lattice. What are its physical properties?
What type crystal lattice at Na 2 SO 4?
CO 2 oxide has low t pl, and quartz SiO 2 – very high (quartz melts at 1725 ° C). What crystal lattices should they have?

TEACHER. We've looked into the guts of things, haven't we? In conclusion, I would like to mention precious stones: diamond, sapphire, emerald, alexandrite, amethyst, pearl, opal, etc. Healing properties have long been attributed to precious stones. It was believed that the amethyst crystal protected against drunkenness and brought happy dreams. Emerald saves from storms. Diamond protects against diseases. Topaz brings happiness in November, and garnet in January.

Precious stones served as a measure of the wealth of princes and emperors. Foreign ambassadors who visited in the 17th century. in Russia, they wrote that they were seized by “quiet horror” at the sight of luxurious outfits royal family, completely studded with precious stones.
On the head of Tsarina Irina Godunova there was a crown, “like a wall with battlements,” divided into 12 turrets, skillfully made of rubies, topazes, diamonds and “ramp pearls”, all around the crown was studded with huge amethysts and sapphires.

It is known that the hat of Prince Potemkin of Tauride was so studded with diamonds and because of this it was so heavy that the owner could not wear it on his head; the adjutant carried the hat in his hands behind the prince. One of Empress Elizabeth's dresses was sewn with so many precious stones that she, unable to bear their weight, fainted at the ball. However, even earlier, a more annoying incident happened to the wife of Tsar Alexander Mikhailovich: she had to interrupt the wedding ceremony in order to take off her outfit strewn with gems.
The largest diamonds in the world are known each by their own name: “Orlov”, “Shah”, “Konkur”, “Regent”, etc.
Crystals are necessary - in watches, echo sounders, microphones; diamond – “worker” (in bearings, glass cutters, etc.).
“Stone now in the hands of man is not fun and luxury, but a wonderful material to which we have managed to return its place, a material among which it is more beautiful and more fun to live. It will not be a “precious stone” - its time has passed: it will be a gem that gives beauty to life. ...In him a person will see the embodiment of the unsurpassed colors and incorruptibility of nature itself, which an artist can only touch with the burning fire of inspiration,” wrote academician A.E. Fersman.
Crystals can be grown even at home. Try some creative crystal growing homework.

Homework
"Growing Crystals"

Equipment and reagents. Clean glasses, cardboard, pencil, thread; water, salt (NaCl, or CuSO 4, or KNO 3.)

Progress

First way. Prepare saturated solution salt of your choice. For this purpose in hot water Add salt in portions and stir until dissolved. As soon as the salt stops dissolving, the solution is saturated. Filter the solution through gauze. Pour this solution into a glass, put a pencil with a thread and a weight (a button, for example). After 2–3 days, the cargo should become covered with crystals.
Second way. Cover the jar with the saturated solution with cardboard and wait until crystals fall to the bottom during slow cooling. Dry the crystals on a napkin, fasten a few of the most attractive ones on a thread, tie them to a pencil and lower them into a saturated solution freed from other crystals. Crystals can take 2-3 weeks to grow.

The molecular structure has

1) silicon(IV) oxide

2) barium nitrate

3) sodium chloride

4) carbon monoxide (II)

Explanation.

The structure of a substance is understood from which particles of molecules, ions, and atoms its crystal lattice is built. Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO 2, SiC (carborundum), BN, Fe 3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Silicon oxide (IV) - covalent bonds, solid, refractory substance, atomic crystal lattice. Barium nitrate and sodium chloride are substances with ionic bonds - an ionic crystal lattice. Carbon (II) monoxide is a gas in a molecule with covalent bonds, which means this is the correct answer, the crystal lattice is molecular.

Answer: 4

Source: Demo version of the Unified State Exam 2012 in chemistry.

In solid form, the molecular structure has

1) silicon(IV) oxide

2) calcium chloride

3) copper (II) sulfate

Explanation.

The structure of a substance is understood from which particles of molecules, ions, and atoms its crystal lattice is built. Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO 2, SiC (carborundum), BN, Fe 3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice. Silicon oxide (IV) - covalent bonds, solid, refractory substance, atomic crystal lattice. Calcium chloride and copper sulfate are substances with ionic bonds - the crystal lattice is ionic. The iodine molecule has covalent bonds, and it easily sublimes, which means this is the correct answer, the crystal lattice is molecular.

Answer: 4

Source: Demo version of the Unified State Exam 2013 in chemistry.

1) carbon monoxide (II)

3) magnesium bromide

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Answer: 3

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Far East. Option 1.

Has an ionic crystal lattice

2) carbon monoxide (II)

4) magnesium bromide

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Magnesium bromide has an ionic crystal lattice.

Answer: 4

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Far East. Option 2.

Sodium sulfate has a crystal lattice

1) metal

3) molecular

4) atomic

Explanation.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Sodium sulfate is a salt that has an ionic crystal lattice.

Answer: 2

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Far East. Option 3.

Each of two substances has a non-molecular structure:

1) nitrogen and diamond

2) potassium and copper

3) water and sodium hydroxide

4) chlorine and bromine

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, SiC (carborundum), BN, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Of the listed substances, only diamond, potassium, copper and sodium hydroxide have a non-molecular structure.

Answer: 2

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Far East. Option 4.

Substance with ionic type crystal lattice is

3) acetic acid

4) sodium sulfate

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Sodium sulfate has an ionic crystal lattice.

Answer: 4

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Siberia. Option 1.

The metal crystal lattice is characteristic of

2) white phosphorus

3) aluminum oxide

4) calcium

Explanation.

A metallic crystal lattice is characteristic of metals, such as calcium.

Answer: 4

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Ural. Option 1.

Maxim Avramchuk 22.04.2015 16:53

All metals except mercury have a metallic crystal lattice. Could you tell me what kind of crystal lattice does mercury and amalgam have?

Alexander Ivanov

Mercury in the solid state also has a metallic crystal lattice.

2) calcium oxide

4) aluminum

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Calcium oxide has an ionic crystal lattice.

Answer: 2

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Siberia. Option 2.

Has a molecular crystal lattice in the solid state

1) sodium iodide

2) sulfur oxide(IV)

3) sodium oxide

4) iron(III) chloride

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Among the given substances, all except sulfur(IV) oxide have an ionic crystal lattice, while it has a molecular lattice.

Answer: 2

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Siberia. Option 4.

Has an ionic crystal lattice

3) sodium hydride

4) nitric oxide(II)

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Sodium hydride has an ionic crystal lattice.

Answer: 3

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Ural. Option 5.

For substances with a molecular crystal lattice, a characteristic property is

1) refractoriness

2) low boiling point

3) high melting point

4) electrical conductivity

Explanation.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Answer: 2

Answer: 2

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Center. Option 1.

For substances with a molecular crystal lattice characteristic property is

1) refractoriness

2) high boiling point

3) low melting point

4) electrical conductivity

Explanation.

Substances with a molecular crystal lattice have lower melting and boiling points than all other substances.

Answer: 3

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Center. Option 2.

The molecular structure has

1) hydrogen chloride

2) potassium sulfide

3) barium oxide

4) calcium oxide

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Of the above substances, all have an ionic crystal lattice except hydrogen chloride.

Answer: 1

Source: Unified State Exam in Chemistry 06/10/2013. Main wave. Center. Option 5.

The molecular structure has

1) silicon(IV) oxide

2) barium nitrate

3) sodium chloride

4) carbon monoxide (II)

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, CaC2, SiC (carborundum), BN, Fe3 C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

Among the listed substances, carbon monoxide has a molecular structure.

Answer: 4

Source: Demo version of the Unified State Exam 2014 in chemistry.

The substance of molecular structure is

1) ammonium chloride

2) cesium chloride

3) iron(III) chloride

4) hydrogen chloride

Explanation.

The structure of a substance is understood from which particles of molecules, ions, and atoms its crystal lattice is built. Substances with ionic and metallic bonds have a non-molecular structure. Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, SiC (carborundum), BN, Fe3C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Substances with a molecular crystal lattice have lower boiling points than all other substances. Using the formula, it is necessary to determine the type of bond in the substance, and then determine the type of crystal lattice.

1) ammonium chloride - ionic structure

2) cesium chloride - ionic structure

3) iron(III) chloride - ionic structure

4) hydrogen chloride - molecular structure

Answer: 4

Which chlorine compound has the highest melting point?

Answer: 3

Which oxygen compound has the highest melting point?

Answer: 3

Alexander Ivanov

No. This is an atomic crystal lattice

Igor Srago 22.05.2016 14:37

Since the Unified State Examination teaches that the bond between metal and non-metal atoms is ionic, aluminum oxide should form an ionic crystal. And substances with an ionic structure (like atomic ones) also have a melting point higher than molecular substances.

Anton Golyshev

It is better to simply learn substances with an atomic crystal lattice.

Uncharacteristic for substances with a metal crystal lattice

1) fragility

2) plasticity

3) high electrical conductivity

4) high thermal conductivity

Explanation.

Metals are characterized by plasticity, high electrical and thermal conductivity, but fragility is not typical for them.

Answer: 1

Source: Unified State Exam 05/05/2015. Early wave.

Explanation.

Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, SiC (carborundum), BN, Fe3C, TaC, red and black phosphorus. This group includes substances, usually solid and refractory substances.

Answer: 1

Has a molecular crystal lattice

Explanation.

Substances with ionic (BaSO 4) and metallic bonds have a non-molecular structure.

Substances whose atoms are connected by covalent bonds can have molecular and atomic crystal lattices.

Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO 2, SiC (carborundum), B 2 O 3, Al 2 O 3.

Substances that are gaseous under normal conditions (O 2, H 2, NH 3, H 2 S, CO 2), as well as liquid (H 2 O, H 2 SO 4) and solid, but fusible (S, glucose), have a molecular structure

Therefore, carbon dioxide has a molecular crystal lattice.

Answer: 2

Has an atomic crystal lattice

1) ammonium chloride

2) cesium oxide

3) silicon(IV) oxide

4) crystalline sulfur

Explanation.

Substances with ionic and metallic bonds have a non-molecular structure.

Substances in whose molecules atoms are connected by covalent bonds can have molecular and atomic crystal lattices. Atomic crystal lattices: C (diamond, graphite), Si, Ge, B, SiO2, SiC (carborundum), BN, Fe3C, TaC, red and black phosphorus. The rest refer to substances with a molecular crystal lattice.

Therefore, silicon(IV) oxide has an atomic crystal lattice.

Answer: 3

A solid, brittle substance with a high melting point, the solution of which conducts electric current, has a crystal lattice

2) metal

3) atomic

4) molecular

Explanation.

Such properties are characteristic of substances with an ionic crystal lattice.

Answer: 1

Which silicon compound has a molecular crystal lattice in the solid state?

It is not individual atoms or molecules that enter into chemical interactions, but substances.

Our task is to get acquainted with the structure of matter.

At low temperatures, substances are in a stable solid state.

☼ The hardest substance in nature is diamond. He is considered the king of all gems and precious stones. And its name itself means “indestructible” in Greek. Diamonds have long been looked upon as miraculous stones. It was believed that a person wearing diamonds does not know stomach diseases, is not affected by poison, retains his memory and a cheerful mood until a very old age, and enjoys royal favor.

☼ A diamond that has been subjected to jewelry processing - cutting, polishing - is called a diamond.

When melting as a result of thermal vibrations, the order of the particles is disrupted, they become mobile, while the nature of the chemical bond is not disrupted. Thus, there are no fundamental differences between solid and liquid states.

The liquid acquires fluidity (i.e., the ability to take the shape of a vessel).

Liquid crystals were discovered at the end of the 19th century, but have been studied in the last 20-25 years. Many display devices modern technology, for example, some electronic watches, mini-computers, operate on liquid crystals.

In general, the words “liquid crystals” sound no less unusual than “hot ice”. However, in reality, ice can also be hot, because... at a pressure of more than 10,000 atm. water ice melts at temperatures above 200 0 C. The unusualness of the combination “liquid crystals” is that the liquid state indicates the mobility of the structure, and the crystal implies strict ordering.

If a substance consists of polyatomic molecules of an elongated or lamellar shape and having an asymmetrical structure, then when it melts, these molecules are oriented in a certain way relative to each other (their long axes are parallel). In this case, the molecules can move freely parallel to themselves, i.e. the system acquires the property of fluidity characteristic of a liquid. At the same time, the system retains an ordered structure, which determines the properties characteristic of crystals.

The high mobility of such a structure makes it possible to control it through very weak influences (thermal, electrical, etc.), i.e. purposefully change the properties of a substance, including optical ones, with very little energy expenditure, which is what is used in modern technology.

Any chemical substance is formed a large number identical particles that are connected to each other.

At low temperatures, when thermal movement difficult, the particles are strictly oriented in space and form crystal lattice.

Crystal cell - This structure with a geometrically correct arrangement of particles in space.

In the crystal lattice itself, nodes and internodal space are distinguished.

The same substance depending on the conditions (p, t,...)exists in various crystalline forms (i.e. they have different crystal lattices) - allotropic modifications that differ in properties.

For example, four modifications of carbon are known: graphite, diamond, carbyne and lonsdaleite.

☼ The fourth variety of crystalline carbon, “lonsdaleite,” is little known. It was discovered in meteorites and obtained artificially, and its structure is still being studied.

☼ Soot, coke, charcoal classified as amorphous carbon polymers. However, it has now become known that these are also crystalline substances.

☼ By the way, shiny black particles were found in the soot, which were called “mirror carbon.” Mirror carbon is chemically inert, heat-resistant, impervious to gases and liquids, has a smooth surface and is absolutely compatible with living tissues.

☼ The name graphite comes from the Italian “graffito” - I write, I draw. Graphite is a dark gray crystal with a weak metallic luster and has a layered lattice. Individual layers of atoms in a graphite crystal, connected to each other relatively weakly, are easily separated from each other.

TYPES OF CRYSTAL LATTICES

If the rate of crystal growth is low upon cooling, a glassy state (amorphous) is formed.

1. The relationship between the position of an element in the Periodic Table and the crystal lattice of its simple substance.

There is a close relationship between the position of an element in the periodic table and the crystal lattice of its corresponding elemental substance.

The simple substances of the remaining elements have a metallic crystal lattice.

FIXING

Study the lecture material and answer the following questions in writing in your notebook:

1. What is a crystal lattice?
2. What types of crystal lattices exist?
3. Characterize 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 → Interaction forces between the particles of the crystal → Physical properties due to the crystal lattice → Aggregate state of the substance under normal conditions → Examples

Complete tasks on this topic:

1. What type of crystal lattice does the following substances widely used in everyday life have: water, acetic acid (CH 3 COOH), sugar (C 12 H 22 O 11), potassium fertilizer (KCl), river sand (SiO 2) - melting point 1710 0 C , ammonia (NH 3), table salt? Make a general conclusion: by what properties of a substance can one determine the type of its crystal lattice?
2. Using 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 physical properties of each of the four substances.
   
3. Trainer No. 1. "Crystal lattices"
   
4. Trainer No. 2. "Test tasks"
   
5. Test (self-control):

1) Substances that have a molecular crystal lattice, as a rule:

2) The concept of “molecule” not applicable in relation to the structural unit of a substance:

a). water

b). oxygen

V). diamond

G). ozone

3) The atomic crystal lattice is characteristic of:

a). aluminum and graphite

b). sulfur and iodine

V). silicon oxide and sodium chloride

G). diamond and boron

4) If a substance is highly soluble in water, it has high temperature melting, electrically conductive, then its crystal lattice:

A). molecular

b). atomic

V). ionic

G). metal