Sulfur allotropy. Sulfur, properties, in nature

The ability of a chemical element to exist in the form of two or more simple substances that differ only in the number of atoms in a molecule, or in structure. Carbon

Allotropy of carbon is due to the different arrangement of atoms in the crystal lattice

Diamond and graphite-atomic crystal lattice, Fullerene molecular (C 60)

Oxygen exists in the form of two allotropic modifications - O 2 and O 3

A substance, the formula of which is O2, is found in the atmosphere, hydrosphere, earth's crust and living organisms. About 20% of the atmosphere is formed by diatomic oxygen molecules. In the stratosphere, at an altitude of about 12-50 km from the earth's surface, there is a layer called the "ozone screen". Its composition reflects the O3 formula. Ozone protects our planet by intensely absorbing the dangerous rays of the sun's red and ultraviolet spectrum.

Comparison of oxygen and ozone

The allotropy of oxygen and ozone is due to the different amount of oxygen in the molecules of substances.

Oxygen allotropy

Allatropium phosphorus

The allotropy of phosphorus is due to the different crystal lattice

Sulfur allatropy

The allotropy of sulfur is due to the different crystal lattice

rhombic ,monoclinic and plastic .

Sulfur in nature

Native sulfur

Ukraine, Volga region, Central Asia and dr

Sulphides

PbS - lead shine

Cu 2 S - copper luster

ZnS - zinc blende

FeS 2 - pyrite, pyrite, cat gold

H 2 S - hydrogen sulfide (in mineral springs and natural gas)

Squirrels

Hair, skin, nails ...

Sulphates

CaSO 4 x 2 H 2 O - gypsum

MgSO 4 x 7 H 2 O - bitter salt (English)

Na 2 SO 4 x 10 H 2 O - Glauber's salt (mirabilite)

Physical properties

Solid crystalline substance of yellow color, insoluble in water, not wetted with water (floats on the surface), t ° bale = 445 ° С

Allotropy

Sulfur is characterized by several allotropic modifications:

Sulfur is a fairly common chemical element in nature (sixteenth in terms of content in the earth's crust and sixth in natural waters). There are both native sulfur (free state of the element) and its compounds.

Sulfur in nature

Among the most important natural ones are iron pyrite, sphalerite, galena, cinnabar, antimonite. In the oceans, it is found mainly in the form of magnesium and sodium, which determine the hardness of natural waters.

How is sulfur obtained?

Sulfur ores are mined by different methods. The main method for producing sulfur is smelting it directly in the field.

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

In industry, sulfur is obtained as a by-product of processes in smelting furnaces, during oil refining. In large quantities, it is present in natural gas (in the form of sulfur dioxide or hydrogen sulfide), during the extraction of which it is deposited on the walls of the equipment used. Finely dispersed sulfur captured 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 Claus method is used. It consists in the use of "sulfur pits" in which sulfur degassing takes place. The result is a modified sulfur widely used in asphalt production.

Major allotropic sulfur modifications

Allotropy is inherent in sulfur. A large number of allotropic modifications are known. The most famous are rhombic (crystalline), monoclinic (acicular) and plastic sulfur. The first two modifications are stable, the third, when solidified, turns into a rhombic one.

Physical properties characterizing sulfur

Molecules of rhombic (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 a rhombic 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 and becomes a yellow liquid, which turns brown at 160 ° C and turns into a viscous dark brown mass when it reaches about 190 ° C. At temperatures above this value, the sulfur viscosity decreases. At about 300 ° C, it changes back into a liquid fluid state. This is due to the fact that sulfur polymerizes during heating, increasing the chain length with increasing temperature. And when a temperature value of over 190 ° C is reached, the destruction of polymer links is observed.

When the sulfur melt is cooled naturally in cylindrical crucibles, the so-called lump sulfur is formed - large-sized rhombic crystals that have a distorted shape in the form of octahedra with partially "cut" edges or corners.

If the molten substance is subjected to sharp cooling (for example, using cold water), then you can get plastic sulfur, which is an elastic rubbery mass of brownish or dark red color with a density of 2.046 g / cm 3. This modification, in contrast to the rhombic and monoclinic, is unstable. Gradually (over several hours) it changes color to yellow, becomes brittle and turns into a rhombic one.

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

Sulfur practically does not dissolve in the aquatic environment. However, it is characterized by good solubility in organic solvents. Poorly conducts electricity and heat.

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 disintegrate, and at temperatures above 900 degrees, the vapors consist practically only of S 2 molecules dissociating into atoms at 1500 ° C.

What are the chemical properties of sulfur?

Sulfur is a typical non-metal. Chemically active. Oxidative - the reducing properties of sulfur are manifested in relation to a variety of elements. When heated, it easily combines with almost all elements, which explains its obligatory presence in metal ores. 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 determine its combustion in air. The result of this interaction is the formation of sulphurous (SO 2) and sulfuric (SO 3) anhydrides, which are used to obtain sulphurous and sulfuric acids.

At room temperature, the reducing properties of sulfur are manifested only in relation to fluorine, in the reaction with which it is formed:

• S + 3F 2 = SF 6.

When heated (in the form of a melt), it interacts with chlorine, phosphorus, silicon, carbon. As a result of reactions with hydrogen, in addition to hydrogen sulphide, 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 are formed) and polysulfides (polysulfur metals).

With prolonged heating, it reacts with concentrated oxidizing acids, oxidizing at the same time.

sulphur dioxide

Sulfur (IV) oxide, also called sulfur dioxide and sulfur dioxide, is a colorless gas with a pungent, suffocating odor. It tends to liquefy under pressure at room temperature. SO 2 is an acidic oxide. It is characterized by good water solubility. In this case, a weak, unstable sulfurous acid is formed, which exists only in an aqueous solution. As a result of the interaction of sulfur dioxide with alkalis, sulfites are formed.

Differs in a rather high chemical activity. The most pronounced are the reducing chemical properties of sulfur (IV) oxide. Such reactions are accompanied by an increase in the oxidation state of sulfur.

The oxidizing chemical properties of sulfur oxide are manifested 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 freeze at temperatures below 16.9 degrees. This forms a mixture of different crystalline modifications of solid sulfur trioxide. The high hygroscopic properties of sulfur oxide cause it to "smoke" in humid air. 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. It melts at minus 86 ° С, boils at minus 60 ° С. Thermally unstable. At temperatures above 400 ° C, hydrogen sulphide decomposes into S and H 2. It is characterized by good solubility in ethanol. It dissolves poorly in water. As a result of dissolution in water, weak hydrosulfuric acid is formed. Hydrogen sulfide is a strong reducing agent.

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

Sulphuric acid

Sulfuric acid (H 2 SO 4) can be of different concentration and purity. In 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. The boiling point increases with increasing acid concentration.

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

The properties of sulfuric acid are most clearly manifested in redox reactions. This is due to 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 an integral part 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 is 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, about 0.2% sulfur).

The beneficial properties of the trace element can hardly be overestimated. Protecting the blood protoplasm, sulfur is an active assistant to the body in the fight against harmful bacteria. Blood clotting depends on its amount, that is, the element helps to maintain its sufficient level. Sulfur also plays an important role in maintaining normal values ​​of the concentration of bile produced by the body.

It is often referred to as the "beauty mineral" because it is essential for maintaining healthy skin, nails and hair. Sulfur has an inherent ability to protect the body from various types of negative environmental influences. This helps to slow down the aging process. Sulfur cleanses the body of toxins and protects against radiation, which is especially important now, given the modern ecological situation.

An insufficient amount of a trace element in the body can lead to poor excretion of toxins, a decrease in immunity and vitality.

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

Sulfur: properties and applications in industry

Sulfur is most widely used for Also, the properties of this substance make it possible to use it for vulcanizing rubber, as a fungicide in agriculture and even as a drug (colloidal sulfur). In addition, sulfur is used for the production of matches and it is included in the sulfur-bitumen compositions for the manufacture of sulfur asphalt.

This concept is widespread in nature. For example, oxygen and ozone are substances that consist only of the chemical element oxygen. How is this possible? Let's figure it out together.

Definition of the concept

Allotropy is the phenomenon of the existence of one chemical element in the form of two or more simple substances. Jens Berzelius, a chemist and mineralogist from Sweden, is rightfully considered its discoverer. Allotropy is a phenomenon that has a lot in common with crystal polymorphism. This caused a long debate among scientists. At present, they have come to the conclusion that polymorphism is characteristic only of solid simple substances.

Allotropy reasons

Not all chemical elements can form several simple substances. The ability to allotropy is due to the structure of the atom. It is most often found in elements with a variable value of the oxidation state. These include semi- and non-metals, inert gases and halogens.

Allotropy can be due to several reasons. These include a different number of atoms, the order of their connection into a molecule, the parallelism of electron spins, the type of crystal lattice. Let's consider these types of allotropy with specific examples.

Oxygen and ozone

This type of allotropy is an example of how a different number of atoms of one chemical element determines the physical and chemical. This also applies to the physiological effect on living organisms. So, oxygen consists of two oxygen atoms, ozone - of three.

What are the differences between these substances? Both are gaseous. Oxygen has no color, taste or smell; it is one and a half times lighter than ozone. This substance is readily soluble in water, and with a decrease in temperature, the rate of this process only increases. Oxygen is essential for all organisms to breathe. Therefore, this substance is vital.

Ozone is blue in color. Each of us felt its characteristic smell after the rain. It's edgy, but pretty sweet. Compared to oxygen, ozone is more chemically active. What is the reason? When ozone decomposes, an oxygen molecule and a free oxygen atom are formed. He immediately enters into the formation of new substances.

The amazing properties of carbon

But the number of atoms in a carbon molecule always remains unchanged. At the same time, it forms completely different substances. The most common carbon modifications are diamond and graphite. The first substance is considered the hardest on the planet. This property is due to the fact that the atoms in the diamond are bound by strong covalent bonds in all directions. Together, they form a three-dimensional network of tetrahedrons.

In graphite, strong bonds are formed only between atoms located in the horizontal plane. For this reason, it is practically impossible to break the graphite rod lengthwise. But the bonds that connect the horizontal layers of carbon to each other are very weak. Therefore, every time we run a simple pencil over the paper, a gray trace remains on it. This is the carbon layer.

Sulfur allotropy

The reason for the sulfur modifications also lies in the peculiarities of the internal structure of the molecules. The most stable form is rhombic. Crystals of this type of sulfur allotropy are called rhomboidal. Each of them is formed by crown-shaped molecules, each of which contains 8 atoms. In terms of physical properties, rhombic sulfur is a yellow solid. She not only does not dissolve in water, but is not even wetted by it. Heat and electrical conductivity is very low.

The structure of monoclinic sulfur is represented by a parallelepiped with beveled corners. the substance resembles needles of a dark yellow color. If sulfur is melted and then placed in cold water, a new modification of it is formed. Its original structure will break down to polymer chains of varying lengths. This is how plastic sulfur is obtained - a rubbery brown mass.

Phosphorus modifications

Scientists count 11 types of phosphorus. Its allotropy was discovered almost by accident, as was the substance itself. In search of the Philosopher's Stone, the alchemist Brand obtained a luminous dry substance as a result of the evaporation of urine. It was white phosphorus. This substance is characterized by high chemical activity. It is enough to raise the temperature to 40 degrees for white phosphorus to react with oxygen and ignite.

For phosphorus, the cause of allotropy is a change in the structure of the crystal lattice. It can only be changed under certain conditions. Thus, by increasing the pressure and temperature in an atmosphere of carbon dioxide, red phosphorus is obtained. Chemically, it is less active, so it does not glow. When heated, it turns into steam. We see this every time we light regular matches. The grating surface contains red phosphorus.

So, allotropy is one chemical element in the form of several simple substances. Most often found among non-metals. The main reasons for this phenomenon are considered to be a different number of atoms forming a molecule of a substance, as well as a change in the configuration of the crystal lattice.

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

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

The external 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 part of the sulfur is found 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 petroleum (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 of mutually perpendicular p-orbitals take part in their formation.

There are three allotropic sulfur modifications: rhombic, monoclinic and plastic. The rhombic and monoclinic modifications are built from cyclic S 8 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 the 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 distinguished in the form of a beveled parallelepiped.

Crystal of rhombic sulfur. Monoclinic Sulfur Crystal

Plastic modification of sulfur is formed by spiral chains of sulfur atoms with left and right rotation axes. These chains are twisted and stretched in the same direction.

Rhombic sulfur is stable at room temperature. When heated, it melts, turning into a yellow, highly mobile liquid; upon further heating, the liquid thickens, since long polymer chains are formed in it. When the melt is slowly cooled, dark yellow needle-like crystals of monoclinic sulfur are formed, and if molten sulfur is poured into cold water, you get plastic sulfur - a rubber-like structure consisting of polymer chains. Plastic and monoclinic sulfur are unstable and spontaneously turn into rhombic.