Download a short report on the topic of sulfur allotropy. Physical and chemical properties of sulfur

Sulfur is a fairly common chemical element in nature (the sixteenth most abundant in the earth's crust and the sixth in natural waters). Both native sulfur (the free state of the element) and its compounds are found.

Sulfur in nature

Among the most important natural ones are iron pyrite, sphalerite, galena, cinnabar, and stibnite. The World Ocean contains mainly magnesium and sodium, which cause the hardness of natural waters.

How is sulfur obtained?

Sulfur ores are mined using different methods. The main way to obtain sulfur is to smelt it directly at its deposits.

Open-pit mining involves the use of excavators to remove rock layers that cover the sulfur ore. After the ore layers are crushed by explosions, they are sent to a sulfur smelter.

In industry, sulfur is obtained as a by-product of processes in smelting furnaces and oil refining. It is present in large quantities in natural gas (in the form of sulfur dioxide or hydrogen sulfide), during the production of which it is deposited on the walls of the equipment used. Fine sulfur collected from gas is used in the chemical industry as a raw material for the production of various products.

This substance can also be obtained from natural sulfur dioxide. For this, the Klaus method is used. It involves the use of “sulfur pits” in which sulfur is degassed. The result is modified sulfur, which is widely used in asphalt production.

Main allotropic modifications of sulfur

Sulfur is characterized by allotropy. A large number of allotropic modifications are known. The most famous are orthorhombic (crystalline), monoclinic (needle-shaped) and plastic sulfur. The first two modifications are stable, the third, upon hardening, turns into a rhombic one.

Physical properties characterizing sulfur

Molecules of the orthorhombic (α-S) and monoclinic (β-S) modifications each contain 8 sulfur atoms, which are connected in a closed cycle by single covalent bonds.

Under normal conditions, sulfur has an orthorhombic modification. It is a yellow crystalline solid with a density of 2.07 g/cm 3 . Melts at 113 °C. The density of monoclinic sulfur is 1.96 g/cm 3, its melting point is 119.3 °C.

When melted, sulfur expands in volume and becomes a yellow liquid, which turns brown at a temperature of 160 °C and turns into a viscous dark brown mass when it reaches about 190 °C. At temperatures above this value, the viscosity of sulfur decreases. At about 300 °C it again turns into a liquid fluid state. This is explained by the fact that during the heating process, sulfur polymerizes, increasing the length of the chain with increasing temperature. And when the temperature reaches above 190 °C, destruction of the polymer links is observed.

When molten sulfur is cooled naturally in cylindrical crucibles, so-called lump sulfur is formed - large rhombic crystals with a distorted shape in the form of octahedrons with partially “cut off” faces or corners.

If the molten substance is subjected to rapid cooling (for example, using cold water), then plastic sulfur can be obtained, which is an elastic rubber-like mass of brownish or dark red color with a density of 2.046 g/cm 3 . This modification, unlike the orthorhombic and monoclinic ones, is unstable. Gradually (over several hours) it changes color to yellow, becomes fragile and turns into a rhombic one.

When sulfur vapor (highly heated) is frozen with liquid nitrogen, its purple modification is formed, which is stable at temperatures below minus 80 °C.

Sulfur is practically insoluble in an aqueous environment. However, it is characterized by good solubility in organic solvents. Conducts electricity and heat poorly.

The boiling point of sulfur is 444.6 °C. The boiling process is accompanied by the release of orange-yellow vapors, consisting mainly of S 8 molecules, which dissociate upon subsequent heating, resulting in the formation of equilibrium forms S 6, S 4 and S 2. Further, when heated, large molecules decompose, and at temperatures above 900 degrees, the vapors consist almost exclusively of S 2 molecules, which dissociate into atoms at 1500 ° C.

What chemical properties does sulfur have?

Sulfur is a typical non-metal. Chemically active. Oxidatively - The reducing properties of sulfur are manifested in relation to many elements. When heated, it easily combines with almost all elements, which explains its essential presence in metal ores. The exceptions are Pt, Au, I 2, N 2 and inert gases. The oxidation states that sulfur exhibits in compounds are -2, +4, +6.

The properties of sulfur and oxygen cause it to burn in air. The result of this interaction is the formation of sulfurous (SO 2) and sulfuric (SO 3) anhydrides, which are used to produce sulfurous and sulfuric acids.

At room temperature, the reducing properties of sulfur appear only in relation to fluorine, in reaction with which it forms:

S + 3F 2 = SF 6.

When heated (in the form of a melt), it interacts with chlorine, phosphorus, silicon, and carbon. As a result of reactions with hydrogen, in addition to hydrogen sulfide, it forms sulfanes, united by the general formula H 2 S X.

The oxidizing properties of sulfur are observed when interacting with metals. In some cases, quite violent reactions can be observed. As a result of interaction with metals, compounds) and polysulfides (polysulfur metals) are formed.

When heated for a long time, it reacts with concentrated oxidizing acids, thereby oxidizing.

Sulfur dioxide

Sulfur (IV) oxide, also called sulfur dioxide and sulfur dioxide, is a gas (colorless) with a pungent, asphyxiating odor. It has the property of liquefying under pressure at room temperature. SO 2 is an acidic oxide. Characterized by good solubility in water. This produces a weak, unstable sulfurous acid, which exists only in an aqueous solution. As a result of the interaction of sulfur dioxide with alkalis, sulfites are formed.

It has quite high chemical activity. The most pronounced are the reducing chemical properties of sulfur (IV) oxide. Such reactions are accompanied by an increase in the degree of sulfur oxidation.

The oxidative chemical properties of sulfur oxide appear in the presence of strong reducing agents (for example, carbon monoxide).

Sulfur trioxide

Sulfur trioxide (sulfuric anhydride) - sulfur (VI). Under normal conditions, it is a colorless, highly volatile liquid characterized by a suffocating odor. It tends to harden at temperatures below 16.9 degrees. In this case, a mixture of different crystalline modifications of solid sulfur trioxide is formed. The high hygroscopic properties of sulfur oxide cause it to “smoke” in humid air conditions. As a result, droplets of sulfuric acid are formed.

Hydrogen sulfide

Hydrogen sulfide is a binary chemical compound of hydrogen and sulfur. H 2 S is a poisonous, colorless gas, characterized by a sweetish taste and the smell of rotten eggs. Melts at minus 86 °C, boils at minus 60 °C. Thermally unstable. At temperatures above 400 °C, hydrogen sulfide decomposes into S and H2. Characterized by good solubility in ethanol. It dissolves poorly in water. As a result of dissolution in water, weak hydrosulfide acid is formed. Hydrogen sulfide is a strong reducing agent.

Flammable. When it burns in the air, you can see a blue flame. In high concentrations it can react with many metals.

Sulfuric acid

Sulfuric acid (H 2 SO 4) can be of different concentrations and purities. In an anhydrous state, it is a colorless, odorless, oily liquid.

The temperature at which the substance melts is 10 °C. The boiling point is 296 °C. It dissolves well in water. When sulfuric acid dissolves, hydrates are formed and a large amount of heat is released. The boiling point of all aqueous solutions at a pressure of 760 mm Hg. Art. exceeds 100 °C. An increase in boiling point occurs with increasing acid concentration.

The acidic properties of a substance appear when it interacts with bases. H 2 SO 4 is a dibasic acid, due to which it can form both sulfates (medium salts) and hydrosulfates (acid salts), most of which are soluble in water.

The properties of sulfuric acid are most clearly manifested in redox reactions. This is explained by the fact that in the composition of H 2 SO 4 sulfur has the highest oxidation state (+6). An example of the manifestation of the oxidizing properties of sulfuric acid is the reaction with copper:

Cu + 2H 2 SO 4 = CuSO 4 + 2H 2 O + SO 2.

Sulfur: beneficial properties

Sulfur is a trace element essential for living organisms. It is a component of amino acids (methionine and cysteine), enzymes and vitamins. This element takes part in the formation of the tertiary structure of the protein. The amount of chemically bound sulfur contained in proteins ranges from 0.8 to 2.4% by weight. The content of the element in the human body is about 2 grams per 1 kg of weight (that is, approximately 0.2% is sulfur).

The beneficial properties of the microelement are difficult to overestimate. By protecting the protoplasm of the blood, sulfur is an active assistant to the body in the fight against harmful bacteria. Blood clotting depends on its quantity, that is, the element helps maintain its sufficient level. Sulfur also plays an important role in maintaining normal concentrations of bile produced by the body.

It is often called the “beauty mineral” because it is essential for maintaining healthy skin, nails and hair. Sulfur has the ability to protect the body from various types of negative environmental influences. This helps slow down the aging process. Sulfur cleanses the body of toxins and protects against radiation, which is especially important nowadays, given the current environmental situation.

An insufficient amount of microelement in the body can lead to poor elimination of toxins, decreased immunity and vitality.

Sulfur is a participant in bacterial photosynthesis. It is a component of bacteriochlorophyll, and hydrogen sulfide is a source of hydrogen.

Sulfur: properties and industrial applications

Sulfur is most widely used for. Also, the properties of this substance allow it to be used for the vulcanization of rubber, as a fungicide in agriculture and even as a medicinal product (colloidal sulfur). In addition, sulfur is used for the production of matches and is included in sulfur-bitumen compositions for the production of sulfur asphalt.

Allotropy (from ancient Greek αλλος “other”, τροπος “turn, property”) the existence of the same chemical element in the form of two or more simple substances, different in structure and properties: the so-called allotropic modifications or allotropic forms.

Sulfur has three allotropic modifications: Orthorhombic Orthorhombic Plastic Monoclinic Orthorhombic sulfur is stable at room temperature. When heated, it melts, turning into a yellow, easily mobile liquid; with further heating, the liquid thickens, as long polymer chains are formed in it. When the melt is slowly cooled, dark yellow needle-shaped crystals of monoclinic sulfur are formed, and if you pour molten sulfur into cold water, you get plastic sulfur - a rubber-like structure consisting of polymer chains. Plastic and monoclinic sulfur are unstable and spontaneously transform into orthorhombic sulfur.

Orthorhombic modification of sulfur The S 8 molecule has the shape of a crown, the lengths of all bonds – S – S – are equal to 0.206 nm and the angles are close to tetrahedral 108°. In rhombic sulfur, the smallest elementary volume has the shape of a rectangular parallelepiped. Rhombic sulfur is yellow in color. Rhombic sulfur crystal

Monoclinic modification of sulfur Monoclinic sulfur melts at 119.3 C. Molten sulfur consists mainly of cyclic S8 molecules and is a mobile yellow liquid. When the melt is heated to temperatures above 160 C, the S8 cycles open, forming long polyatomic chains, the melt gradually loses its fluidity and changes color: from yellow it becomes dark brown. At temperatures above 187 C, the chains break and shorten, and the viscosity of molten sulfur decreases. Monoclinic sulfur is pale yellow in color.

Plastic modification of sulfur If molten sulfur is poured into cold water, a brown mass similar to rubber is formed. This is the third allotropic modification of sulfur - plastic sulfur. It consists of irregularly located zigzag chains S n, where n reaches several thousand. It is unstable and after some time it will become brittle and turn yellow, i.e. will gradually turn into a rhombic shape.

Sulfur is one of the few substances that has been known since ancient times; it was used by the first chemists. One of the reasons for the popularity of sulfur is the prevalence of native sulfur in the countries of ancient civilizations. It was developed by the Greeks and Romans, and sulfur production increased significantly after the invention of gunpowder.

Sulfur is located in group 16 of Mendeleev's Periodic Table of Chemical Elements.

The outer energy level of the sulfur atom contains 6 electrons, which have the electronic configuration 3s 2 3p 4. In compounds with metals, sulfur exhibits a negative oxidation state of elements -2, in compounds with oxygen and other active non-metals - positive +2, +4, +6. Sulfur is a typical non-metal; depending on the type of transformation, it can be an oxidizing agent and a reducing agent.

Sulfur is quite widespread in nature. Its content in the earth's crust is 0.0048%. A significant portion of sulfur occurs in the native state.

Sulfur is also found in the form of sulfides: pyrite, chalcopyrite and sulfates: gypsum, celestine and barite.

Many sulfur compounds are found in oil (thiophene C 4 H 4 S, organic sulfides) and petroleum gases (hydrogen sulfide).

The existence of allotropic modifications of sulfur is associated with its ability to form stable homochains - S - S -. The stability of the chains is explained by the fact that the bonds - S - S - are stronger than the bond in the S 2 molecule. Sulfur homochains have a zigzag shape, since electrons from mutually perpendicular p-orbitals take part in their formation.

There are three allotropic modifications of sulfur: rhombic, monoclinic and plastic. The rhombic and monoclinic modifications are constructed from cyclic S8 molecules located at the sites of the rhombic and monoclinic lattices.

The S 8 molecule has the shape of a crown, the lengths of all bonds - S - S - are equal to 0.206 nm and the angles are close to tetrahedral 108°.

In rhombic sulfur, the smallest elementary volume has the shape of a rectangular parallelepiped, and in the case of monoclinic sulfur, the elementary volume is allocated in the form of a beveled parallelepiped.

Rhombic sulfur crystal. Monoclinic sulfur crystal

The plastic modification of sulfur is formed by helical chains of sulfur atoms with left and right axes of rotation. These chains are twisted and pulled in one direction.

Orthorhombic sulfur is stable at room temperature. When heated, it melts, turning into a yellow, easily mobile liquid; with further heating, the liquid thickens, as long polymer chains are formed in it. When the melt is slowly cooled, dark yellow needle-shaped crystals of monoclinic sulfur are formed, and if you pour molten sulfur into cold water, you get plastic sulfur - a rubber-like structure consisting of polymer chains. Plastic and monoclinic sulfur are unstable and spontaneously transform into orthorhombic sulfur.

Lesson summary on the topic: “Sulfur. Allotropy of sulfur. Properties and application",

9th grade. UMK G.E. Rudzitis and F.G. Feldman.

Chemistry teacher of the Municipal State Educational Institution “Secondary School No. 85 named after Hero of the Soviet Union N.D. Pakhotishcheva, Taishet"Nikityuk Lyubov Fedorovna.

The purpose of the lesson:review the structure of the sulfur atom based on position in the periodic table, physical and chemical properties, allotropy and uses of sulfur.

Lesson objectives:

Educational:

Consider the structure of the sulfur atom based on its position in the periodic table of chemical elements D.I. Mendeleev, allotropic modifications of sulfur.

Study the physical and chemical properties of sulfur, its redox duality, occurrence in nature, areas of application.

Continue to develop students’ skills in working with the periodic table of chemical elements D.I. Mendeleev.

Improve the ability to write equations of chemical reactions and conduct experiments.

Educational:

Develop memory and attention of students.

Form positive motivation for studying the subject.

Learn to apply existing knowledge to a new situation.

Educational:

To develop communication skills through student work in pairs.

Show the importance of chemical knowledge for modern man.

Continue the formation of such personality qualities as a responsible attitude to the assigned work, the ability to evaluate the results of one’s work.

Conceptual apparatus:native sulfur, sulfide, sulfate, allotropy, demercurization.

Equipment:PSHE,computer, “Minerals” collection,computer presentation in the programPower Point; sulfur; alcohol lamp; matches; holder; rack with test tubes, water.

For laboratory experiments of students: the “Minerals” collection, a sample of sulfur, water in a glass, a glass rod.

Lesson type:combined. A lesson in learning new material.

Forms of organizing educational activities:

Independent work with the textbook text;

Frontal;

Work in pairs;

Laboratory work,

Student messages.

Methods and methodological techniques:

Partially searchable.

Verbal (heuristic conversation);

Visual;

Performing laboratory experiments;

Listening to messages;

Practical (demonstration - chemical experiment, laboratory experience)

Performing physical education.

Pedagogical techniques:

Educational and organizational (defining the purpose and objectives of the lesson, creating favorable conditions for activity);

Educational and informational (conversation, problem statement, discussion, work with a textbook, observation);

Educational and intellectual (perception, comprehension, memorization of information, problem solving, motivation of activity).

During the classes

Lesson stages, time

Forms of interaction

Methods and techniques

Teacher activities

Planned student activity

Slide No.

Organizing time

1 min.

Frontal

Conversation

I greet the students, ask if everyone is in the class, and set them up for the lesson.

Greetings from the teachers.

Updating knowledge

5 minutes.

Frontal

Creating a problem situation

Guys, guess the riddle.

Golden substance:

Grapes are pollinated with it in the summer.

You can see this picture:

Rubber turns into rubber.

“Sulphur” is the topic of our lesson.

What questions should we consider in class today?

They listen and guess the riddle. This is sulfur.

Write down the topic in your notebook.

Provide a plan for working on the topic:

Position of sulfur in the periodic table

Atomic structure

Being in nature

Physical properties

Chemical properties

Application

Meaning for humans

Slide No. 1

Learning new material

20-23 min.

Frontal

Conversation

Raising the problem

Practical method

I propose to consider the position of sulfur in the periodic table.

Assignment: draw up diagrams of the structure of the sulfur atom, electronic and graphic formula. Determine the oxidation state of sulfur.

Question: in what form do you think sulfur is found in nature?

Sulfur belongs to the group of “chalcogens,” which translates as “giving birth to ores.”

ExecuteLaboratory experiment No. 4 “Acquaintance with samples of sulfur and its natural connections" (textbook p. 43).

Exercise:examine the sulfur sample. Determine the state of aggregation and color of sulfur. Test the solubility of sulfur in water.

Working with the periodic table

A student at the blackboard draws up a diagram of the structure of the atom, electronic and graphic formulas,

Determine the oxidation degree of sulfur.

Answer:in free form and in the form of chemical compounds.

Students complete LO No. 4, then conduct a check.

Notebook work: sulfur is a crystalline substance, yellow in color, insoluble in water. Does not conduct current or heat.

Slide No. 3

Frontal

Independent work with the textbook

Individual work

Raising the problem

Demonstration experiment: transformation of crystalline sulfur into plastic.

Physical education minute

Verbal

Individual work

Student message

Conversation:

What is called allotropy?

What types of allotropy are characteristic of sulfur?

(Look at the figure “Allotropy of sulfur” and page 29 of the textbook)

I heat the sulfur and pour it into cold water.

Question.What modification of sulfur is discussed in the poem:

Which sulfur has a crown,

But there are no subjects, no throne.

Sulfur puts on a crown when it is stable.

I invite everyone to have a physical education session.

Chemical properties of sulfur.

Questions:

What oxidizing or reducing properties does sulfur have?

(find the answer in the textbook on page 30)

Exercise: complete the reaction equations:

S + H 2 =

S+Na=

S + Fe =

S + Hg =

S+O 2 =

S + F 2 =

Question: what is called demercurization?

Several students receive a task on a card: to carry out a transformation according to the scheme:

H 2 S→S→Al 2 S 3 →Al(OH) 3

It remains for us to consider the use of sulfur.

Thus, during the lesson we looked at the properties of sulfur. Let's turn to the topic of the lesson, did we find the answer to all your questions?

Answer:allotropy is the phenomenon of the existence of simple substances formed by the same chemical element.

Allotropic modifications of sulfur – crystalline and plastic sulfur.

Write down the properties of allotropic modifications in a notebook.

Students perform exercises along with the video.

Students express their guesses.

In reactions with oxygen, sulfur is a reducing agent. Exhibits oxidation states of +4 and +6.

In reactions with hydrogen and metals, sulfur is an oxidizing agent. Exhibits an oxidation state of -2.

Students write reactions:

S+H 2 =H 2 S

S+2Na=Na 2 S

S + Fe = FeS

S + Hg = HgS

S+O 2 =SO 2

S + 3 F 2 = SF 6

Answer: Cleaning premises and objects from contamination with metallic mercury and sources of mercury vapor is called demercurization.

Assignments are performed at the board and on the spot.

Student's story about the biological role and use of sulfur:

In ancient times, sulfur was used to make paints, cosmetics and gunpowder. In the modern world, sulfur has the widest application. Without it, life is impossible in the literal sense of the word. Sulfur is part of organic substances - proteins, from which all living things are composed. The use of sulfur can be very modestly represented in the form of a diagram (slide No. 9)

Sample student answers:

We looked at the properties of sulfur: physical and chemical

Found out where sulfur occurs in nature

Considered the allotropy of sulfur

Considered the use of sulfur

Slide No. 4

Slide No. 5

Slide No. 6

Slide No. 7

and No. 8

Slide No. 9

Primary consolidation of knowledge

5 minutes.

Group (pair)

Independent work

Pair check

Exercise:choose the correct statements

(questions are printed on pieces of paper)

1.Structure of the sulfur atom:

a) + 15)2)8)5

b) + 17)2)8)7

c) + 16)2)8)6

d) + 18)2)8)8

2. The most characteristic oxidation states for the sulfur atom are:

a) -2; +2; +4; +6

b) -2; +4; +5; +6

at 2; +1; +3; +6

d) -2; +2; +4; +5

3. Which modification does not exist:

a) rhombic

b) tetrahedral

c) monoclinic

d) plastic

4. Sulfur does not dissolve in:

a) acetone

b) water

c) carbon disulfide

d) toluene

5. At room temperature, sulfur reacts with metal:

a) iron

b) zinc

c) aluminum

d) mercury

Perform the test

Carry out a procedure for self- and mutual assessment of their own educational activities and their comrades in the lesson

by key:

1 – in

2 – a

3 – b

4 – b

5 – g

Slide No. 10

Reflection

3 min.

Front work

I have students select an unfinished sentence on the screen and continue with it.

(slide number 11)

Finish the sentence by expressing their attitude to the lesson or topic.

Slide No. 11

Homework, commenting on lesson grades

3 min.

Frontal

Sulfur is located in group VIa of the Periodic Table of Chemical Elements D.I. Mendeleev.
The outer energy level of sulfur contains 6 electrons, which have 3s 2 3p 4. In compounds with metals and hydrogen, sulfur exhibits a negative oxidation state of elements -2, in compounds with oxygen and other active non-metals - positive +2, +4, +6. Sulfur is a typical non-metal; depending on the type of transformation, it can be an oxidizing agent and a reducing agent.

Finding sulfur in nature

Sulfur is found in a free (native) state and bound form.

The most important natural sulfur compounds:

FeS 2 - iron pyrite or pyrite,

ZnS - zinc blende or sphalerite (wurtzite),

PbS - lead luster or galena,

HgS - cinnabar,

Sb 2 S 3 - stibnite.

In addition, sulfur is present in oil, natural coal, natural gases, and natural waters (in the form of sulfate ions and determines the “permanent” hardness of fresh water). A vital element for higher organisms, an integral part of many proteins, is concentrated in the hair.

Allotropic modifications of sulfur

Allotropy- this is the ability of the same element to exist in different molecular forms (molecules contain different numbers of atoms of the same element, for example, O 2 and O 3, S 2 and S 8, P 2 and P 4, etc.).

Sulfur is distinguished by its ability to form stable chains and cycles of atoms. The most stable are S8, which form orthorhombic and monoclinic sulfur. This is crystalline sulfur - a brittle yellow substance.

Open chains have plastic sulfur, a brown substance, which is obtained by sharp cooling of molten sulfur (plastic sulfur becomes brittle after a few hours, acquires a yellow color and gradually turns into rhombic).

1) rhombic - S 8

t°pl. = 113°C; r = 2.07 g/cm 3

The most stable modification.

2) monoclinic - dark yellow needles

t°pl. = 119°C; r = 1.96 g/cm 3

Stable at temperatures above 96°C; under normal conditions it turns into rhombic.

3) plastic - brown rubber-like (amorphous) mass

Unstable, when hardening it turns into a rhombic