The division of chemical elements into metals and non-metals is rather arbitrary. There is a small group of elements that behave atypically under certain conditions. For example, aluminum can react not only with acids, like most metals, but also with alkalis, like non-metallic elements. And germanium, which is a non-metal, can conduct electricity like a typical metal. In our article, we will consider the physical and Chemical properties non-metals, as well as their application in industry.
The differences in the characteristics of elements are based on the structure of their atoms. Nonmetals have 4 to 8 electrons at the last energy level, except for hydrogen, helium and boron. Almost all non-metals are p-elements. For example, it is chlorine, nitrogen, oxygen. Helium and hydrogen, which are p-elements, do not obey this rule. The physical properties of non-metals, as well as the ability to chemical transformations, are due to their location in the periodic system.
A change in the properties of atoms of non-metallic elements occurs with an increase in the serial number. In a period, due to an increase in the charge of the nucleus, the atom is compressed and its radius decreases. The oxidizing ability is also enhanced, and the reducing properties of the elements are weakened. The physical properties of non-metals, as well as the features of their interaction with other substances, depend on the structure of their external energy level. The ability of atoms to attract foreign electrons into their sphere of influence also depends on it. For example, in the second period from boron to fluorine, the electronegativity of non-metals increases. The most active among all non-metallic elements is fluorine. In its compounds, it retains foreign electrons most strongly, retaining a charge of -1.
Nonmetals exist in various states of aggregation. So, boron, carbon, phosphorus are solid compounds, bromine is a liquid, nitrogen, hydrogen, oxygen are gases. All of them do not conduct electric current, are less durable than metals, and have low thermal conductivity. The type of crystal lattice also affects the physical properties of non-metals. For example, compounds with a molecular lattice (iodine, sulfur, phosphorus) have a low boiling and melting point, and are also volatile. The atomic crystalline structure is inherent in silicon, diamond. These substances are very durable, their melting and boiling points are high.
The direct reaction of the combination of metals and non-metals leads to the production of binary compounds of the class of salts: nitrides, carbides, chlorides.
For example:
6Na + N 2 \u003d 2 Na 3 N.
Non-metallic elements are able to interact with each other. The main condition for such processes to occur is that the elements must have different electronegativity. For example:
6Cl 2 + 4P \u003d 4 PCl 3.
Most non-metals, with the exception of iodine, are directly oxidized by oxygen. In this case, binary compounds are formed - acid oxides:
C + O 2 \u003d CO 2 - carbon dioxide, or carbon dioxide.
Reactions of non-metals with some oxides are possible. Thus, carbon is used as an element that reduces metals from their oxides:
C + CuO = Cu + CO.
Acids - strong oxidizing agents (for example, nitrate), are able to interact with non-metals, oxidizing them to oxides:
C + 4HNO 3 \u003d CO 2 + 4NO 2 + 2H 2 O.
Elements located in the main subgroup of the seventh group of the table periodic system, are chemically the most active non-metals. Their atoms have the same number of electrons -7 at the last energy level, which explains the similarity of their chemical characteristics.
The physical properties of simple substances - non-metals are different. So, fluorine, chlorine are in the gaseous phase, bromine is a liquid, and iodine is inherent in the solid state. The activity of halogens in the group decreases with an increase in the charge of the atomic nucleus, fluorine is the most reactive among halogens. In reactivity, only oxygen, which is part of the chalcogen group, steps in. The strength of hydrogen compounds of halogens, whose aqueous solutions are acids, increases from fluorine to iodine, and the solubility of sparingly soluble salts decreases. The special position of fluorine among halogens also concerns its ability to react with water. The halogen can decompose water into various products: its own oxide F 2 O, ozone, oxygen, and hydrogen peroxide.
The element is the most common on Earth. Its content in the soil is more than 47%, and the mass of gas in the air is 23.15%. The general physical properties of non-metals, such as nitrogen, oxygen, hydrogen, in a gaseous state, are determined by the structure of their molecules.
All of them consist of two atoms linked by covalent non-polar bonds. In the oxygen atom at the last energy level there are two free p-electrons. Therefore, the oxidation state of the element is usually -2, and in compounds with fluorine (for example, OF 2) +2. Oxygen is poorly soluble in water, at a temperature of -183 ⁰C it turns into an easily mobile liquid. blue color that can be attracted by a magnet. The element is represented by two simple substances: oxygen O 2 and ozone O 3. The characteristic smell of ozone can be felt in the air after a thunderstorm. The substance is extremely aggressive, decomposing organic materials and oxidizing even passive metals such as platinum or gold. Most complex substances - oxides, salts, bases and acids - contain oxygen atoms in their molecules.
Like oxygen, sulfur is very common in the earth's crust, its atoms are also part of organic substances, such as proteins. The sulfur content is high in geothermal springs and volcanic gases. The most common sulfur-containing minerals are pyrite FeS 2 , zinc and lead sheen ZnS, PbS.
To the request: "List the physical properties of non-metals", we can answer by naming, for example, the properties of sulfur. She is a dielectric. The substance poorly retains thermal energy, is brittle, crumbles upon impact, and does not dissolve in water. It can form several allotropic forms, called rhombic, plastic and monoclinic. Natural sulfur has a yellow color and a rhombic structure. AT chemical reactions with metals and some non-metals it behaves as an oxidizing agent, and with halogens and oxygen it exhibits reducing properties.
In our article, using the example of halogens, oxygen and sulfur, we examined the properties of non-metallic elements.
This definition leaves aside the elements of group VIII of the main subgroup - inert or noble gases, the atoms of which have a complete outer electron layer. The electronic configuration of the atoms of these elements is such that they cannot be attributed to either metals or non-metals. They are the objects that natural system elements are clearly divided into metals and non-metals, occupying a boundary position between them. Inert or noble gases (“nobility” is expressed in inertness) are sometimes referred to as non-metals, but purely formally, according to physical characteristics. These substances retain their gaseous state down to very low temperatures.
The chemical inertness of these elements is relative. For xenon and krypton compounds with fluorine and oxygen are known. Undoubtedly, in the formation of these compounds, inert gases acted as reducing agents.
From the definition of non-metals, it follows that their atoms are characterized by high values of electronegativity. Oia varies from 2 to 4. Non-metals are elements of the main subgroups, mainly p elements, with the exception of hydrogen - an s-element.
All non-metal elements (except hydrogen) occupy the upper right corner in the Periodic Table of Chemical Elements of D. I. Mendeleev, forming a triangle, the apex of which is fluorine.
However, special attention should be paid to the dual position of hydrogen in the Periodic system: in groups I and VII of the main subgroups. This is no coincidence. On the one hand, the hydrogen atom, like the atoms of alkali metals, has one electron on the outer (and only for it) electron layer (electronic configuration 1s1), which it is able to donate, showing the properties of a reducing agent.
In most of its compounds, hydrogen, like alkali metals, exhibits an oxidation state of +1, but the release of an electron by a hydrogen atom is more difficult than that of alkali metal atoms. On the other hand, the hydrogen atom, like the halogen atoms, lacks one electron to complete the outer electron layer, so the hydrogen atom can accept one electron, showing the properties of an oxidizing agent and the oxidation state characteristic of a halogen -1 in hydrides - compounds with metals, similar to metal compounds with halogens - halides. But the attachment of one electron to a hydrogen atom is more difficult than with halogens.
Under normal conditions, hydrogen H2 is a gas. Its molecule, like the halogens, is diatomic.
The atoms of nonmetals are dominated by oxidizing properties, that is, the ability to accept electrons. This ability is characterized by the value of electronegativity, which naturally changes in periods and subgroups (Fig. 47).
Fluorine- the strongest oxidizing agent, its atoms in chemical reactions are not able to donate electrons, that is, exhibit reducing properties.
Outer electron layer configuration
Other non-metals can exhibit reducing properties, although to a much weaker extent compared to metals; in periods and subgroups, their restorative ability changes in reverse order compared to oxidative.
There are only 161 non-metal chemical elements. Quite a few, considering that 114 elements are known. Two non-metal elements make up 76% of the mass of the earth's crust. These are oxygen (49%) and silicon (27%). The atmosphere contains 0.03% of the mass of oxygen in the earth's crust. Non-metals make up 98.5% of the mass of plants, 97.6% of the mass of the human body. Six non-metals - C, H, O, N, P and S - biogenic elements that form the most important organic substances of a living cell: proteins, fats, carbohydrates, nucleic acids. The composition of the air we breathe includes simple and complex substances, also formed by the element of non-metals (oxygen O2, nitrogen, carbon dioxide CO2, water vapor H2O, etc.).
Hydrogen- the main element of the universe. Many space objects (gas clouds, stars, including the Sun) are more than half made up of hydrogen. On Earth, it, including the atmosphere, hydrosphere and lithosphere, is only 0.88%. But this is by mass, and the atomic mass of hydrogen is very small. Therefore, its small content is only apparent, and out of every 100 atoms on Earth, 17 are hydrogen atoms.
In simple substances, the atoms of non-metals are connected by a covalent non-polar bond. This results in a more stable electronic system than isolated atoms. In this case, single (for example, in molecules of hydrogen H2, halogens Ru, Br2), double (for example, in sulfur molecules, triple bonds (for example, covalent bonds in nitrogen molecules) are formed.
As you already know simple substances- non-metals may have:
1. Molecular structure. Under ordinary conditions, most of these substances are gases or solids, and only one bromine (Br2) is a liquid. All these substances have a molecular structure, therefore they are volatile. In the solid state, they are fusible due to the weak intermolecular interaction that keeps their molecules in the crystal, and are capable of sublimation.
2. Atomic structure. These substances are formed by long chains of atoms. Due to the high strength of covalent bonds, they, as a rule, have high hardness, and any changes associated with the destruction of the covalent bond in their crystals (melting, evaporation) are performed with a large expenditure of energy. Many of these substances have high melting and boiling points, and their volatility is very low. (In figure 47, the symbols of those non-metal elements that form only atomic crystal lattices are underlined.)
Many non-metal elements form several simple substances - allotropic modifications. As you remember, this property of atoms is called allotropy. Allotropy may also be associated with different composition molecules, and with different crystal structures. Allotropic modifications of carbon are graphite, diamond, carbine, fullerene (Fig. 48).
Non-metal elements with the property of allotropy are indicated in Figure 47 with an asterisk. So simple non-metal substances much more than chemical elements - non-metals.
You know that the length of most metals, with rare exceptions (gold, copper and some others), is characterized by a silvery-white color. But in simple non-metal substances, the range of colors is much more diverse.
Despite the great differences in the physical properties of non-metals, some of their common features should still be noted. All gaseous substances, liquid bromine, as well as typical covalent crystals are dielectrics, since all the outer electrons of their atoms are used to form chemical bonds. Crystals are non-plastic, and any deformation causes the destruction of covalent bonds. Most non-metals do not have a metallic sheen.
As we have already noted, for the atoms of non-metals, and consequently, for the simple substances formed by them, both oxidizing and reducing properties are characteristic.
1. The oxidizing properties of non-metals are manifested primarily when they interact with metals (as you know, metals are always reducing agents):
The oxidizing properties of chlorine Cl2 are more pronounced than those of sulfur, and therefore the metal Pe, which has stable oxidation states +2 b +3 in compounds. oxidized to a higher oxidation state.
2. Most non-metals exhibit oxidizing properties when interacting with hydrogen. As a result, volatile hydrogen compounds are formed.
3. Any non-metal acts as an oxidizing agent in reactions with those non-metals that have a lower value of electronegativity:
The electronegativity of sulfur is greater than that of phosphorus, so it exhibits oxidizing properties here.
The electronegativity of fluorine is greater than that of all other chemical elements, so it exhibits the properties of an oxidizing agent.
Fluorine is the strongest non-metal oxidizing agent, exhibiting only oxidizing properties in reactions.
4. Non-metals also exhibit oxidizing properties in reactions with some complex substances. Not only oxygen, but also other non-metals can also be oxidizing agents in reactions with complex substances - inorganic and organic.
The strong oxidizing agent chlorine Cl2 oxidizes iron(II) chloride to iron(III) chloride.
You remember, of course, the qualitative reaction to unsaturated compounds - the decolorization of bromine water.
When considering the reaction of non-metals with each other, we have already noted that, depending on the values of their electronegativity, one of them exhibits the properties of an oxidizing agent, and the other - the properties of a reducing agent.
1. In relation to fluorine, all non-metals (even oxygen) exhibit reducing properties.
2. Of course, non-metals, except for fluorine, serve as reducing agents when interacting with oxygen:
8 Many nonmetals can act as a reducing agent in reactions with complex oxidizing substances:
There are also reactions in which the same non-metal is both an oxidizing agent and a reducing agent, these are autoxidation-self-recovery reactions.
So let's sum it up! Most non-metals can act in chemical reactions both as an oxidizing agent and as a reducing agent (reducing properties are not inherent in fluorine alone).
A common property of all non-metals is the formation of volatile hydrogen compounds, in most of which the non-metal has the lowest oxidation state.
It is known that these compounds can most simply be obtained directly by the interaction of a non-metal with hydrogen, that is, by synthesis.
Vm hydrogen compounds of non-metals are surrounded by conalent polar ions, have a molecular structure and under normal conditions are gases, except for water (liquid). All hydrogen compounds of non-metals are characterized by a ferrous relation to water. Metai and enlan are practically insoluble in it. Ammonia, when dissolved in water, forms a weak base - ammonia hydrate.
In addition to the considered properties, hydrogen compounds of non-metals in redox reactions always exhibit reductive properties, because in them the non-metal has the lowest oxidation state.
In oxides of non-metals, the bond between atoms is covalent polar. Among the oxides of the molecular structure there are gaseous, liquid (volatile), solid (volatile).
Non-metal oxides are divided into two groups: non-salt-forming and gel-forming. When acid oxides are dissolved in water, oxide hydrates are formed - hydroxides, which are acids in nature. Acids and acid oxides, as a result of chemical reactions, form salts in which the non-metal retains its oxidation state.
Oxides and their corresponding hydroxides - acids in which the non-metal exhibits an oxidation state equal to the group number, that is, its highest value, are called the highest. By revising Periodic Law we have already characterized their composition and properties.
enhancement of the acidic properties of oxides and hydroxides Within the limits of one main subgroup, for example, group VI, the following pattern of changes in the properties of higher oxides and hydroxides operates.
If a non-metal forms two or more acidic oxides, and hence the corresponding oxygen-containing acids, then their acidic properties increase with an increase in the degree of oxidation of the non-metal.
Oxides and acids, in which the non-metal has the highest oxidation state, can only exhibit oxidizing properties.
Oxides and acids, where the non-metal has an intermediate oxidation state, can exhibit both oxidizing and reducing properties.
1. Which electronic families will non-metal elements fall into?
2. What non-metal elements are biogenic?
3. What factors determine the valence capabilities of atoms of nonmetals? Consider them using the example of oxygen and sulfur atoms.
4. Why are some non-metals under normal conditions - gases, others - solid refractory substances? 5. Give examples of simple non-metal substances that exist under normal conditions in different states of aggregation: a) gaseous, b) liquid, c) solid.
6. Make equations for redox reactions involving non-metals. What properties (oxidizing or reducing) do nonmetals exhibit in these reactions?
Why are the boiling points of water and hydrogen sulfide very different, but the boiling points of hydrogen sulfide and hydrogen selenide are close to each other?
7. Why is methane stable in air, but it ignites spontaneously in air: hydrogen fluoride is resistant to heating, iodine-hydrogen decomposes into iodine and hydrogen even at low heating?
8. Write the reaction equations with which you can make the following transitions:
9. Write the reaction equations with which you can make the following transitions:
12. 20 g of hydrogen sulfide was passed through a solution containing 10 g of sodium hydroxide. What kind of salt and how much?
Answer: 0.25 mol NaHS.
14. When treating 30 g of limestone with hydrochloric acid, 11 g of carbon dioxide was obtained. What is the mass fraction of calcium carbonate in natural limestone? Answer: 83.3%. 15. Iodine tincture used in medicine is a 51% solution of crystalline iodine in ethyl alcohol. What is the volume of alcohol, the density of which is 0.8 g / ml. required to prepare 250 g of such a solution?
Answer: 297 ml. 16. A mixture of silicon, graphite and calcium carbonate. A mass of 34 g was treated with a solution of sodium hydroxide and 22.4 liters of gas (n.a.) were obtained. When processing such a portion of the mixture with hydrochloric acid, 2.24 liters of gas (n.a.) were obtained. Determine the mass composition of the mixture.
Answer: 14 g 81: 10 g C; 10 g CaCO2.
17. Gaseous ammonia with a volume of 2.24 l (n.a.) absorbed by 20 g of solution phosphoric acid with a mass fraction of 49%. What salt was formed, what is its mass?
Answer: 11.5g
19. What volume of ammonia is required to obtain 6.3 tons of nitric acid, assuming losses in production equal to 5%?
Answer: 2352 m3.
20. Acetylene was obtained from natural gas with a volume of 300 liters (n.a.) with a volume fraction of methane in the gas of 96%. Determine its volume if the product yield is 65%.
Answer: 93.6 liters.
21. Determine the structural formula of a hydrocarbon with an air vapor density of 1.862 and a mass fraction of carbon of 88.9%. It is known that the hydrocarbon interacts with the ammonia solution of silver oxide.
Non-metals in human life play a huge role, since without them life is impossible not only for humans, but also for other living organisms. Indeed, thanks to such non-metallic elements as oxygen, carbon, hydrogen and nitrogen, amino acids are formed, from which proteins are then formed, without which all life on Earth cannot exist.
Let's take a closer look at the picture below, which shows the main non-metals:
And now let's look at some non-metals in more detail and find out their significance that they play in a person's life and in his body.
A full-fledged human life depends on the air that he breathes, and the air contains non-metals and compounds between them. Provision essential functions our body, oxygen is involved, and nitrogen and other gaseous substances dilute it, and thereby protect our respiratory tract. After all, from the biology course you already know that all the protective functions of the body are closely related to the presence of oxygen.
From the penetration of harmful UV radiation, ozone becomes the protection of our body.
Such an essential microelement as sulfur acts as a beauty mineral in the human body, because thanks to it, the skin, nails and hair will remain healthy. Also, do not forget that sulfur takes part in the formation of cartilage and bone tissues, helps to improve the functioning of joints, strengthens our muscle tissue and performs many other functions that are very important for human health.
Chlorine anions also play an important biological role for humans, as they are involved in the activation of certain enzymes. With their help, a favorable environment in the stomach is maintained and osmotic pressure is maintained. Chlorine, as a rule, enters the human body, thanks to table salt when eating.
Apart from important qualities, which non-metals have on human body, and other living organisms, these substances are also used in various other industries.
Hydrogen
Such a variety of non-metals as hydrogen is widely used in the chemical industry. It is used for the synthesis of ammonia, methanol, hydrogen chloride, as well as for the hydrogenation of fats. Also, one cannot do without the participation of hydrogen as a reducing agent and in the production of many metals and their compounds.
Hydrogen is also widely used in medicine. When treating wounds and to stop minor bleeding, a three percent solution of hydrogen peroxide is used.
Chlorine
For production of hydrochloric acid, rubber, vinyl chloride, plastics, as well as many organic substances, chlorine is used. It is used in industries such as textiles and paper as a bleaching agent. On household level, chlorine is indispensable for the disinfection of drinking water, since, having oxidizing properties, it has a strong disinfecting effect. Chlorine water and lime have the same properties.
For medical purposes, as a rule, sodium chloride is used as a saline solution. Many water-soluble drugs are produced on its basis.
Sulfur
Such a non-metal as sulfur is used for the production of sulfuric acid, gunpowder, matches. It is also used in the vulcanization of rubber. It is used in the production of dyes and phosphors. And colloidal sulfur is necessary in medicine.
Sulfur has found application in agriculture. It is used as a fungicide to control various pests.
In the synthesis of polymeric materials, as well as for the manufacture of various medical preparations, wide application received and such non-metals as iodine and bromine.
Non-metals - elements that have non-metallic properties and occupy a position in the upper right corner in the periodic table. What is the nature of non-metals, as well as how they differ from other compounds, we learn in this article.
Non-metallic elements include p-elements, as well as hydrogen and helium, which in turn belong to s-elements. They are located to the right and above the boron-astatine diagonal. In total, 22 non-metals are known. In the most typical non-metals, the filling of the outer level with electrons is close to the maximum, and the atomic radii are minimal among the elements of this period.
Rice. 1. The group of non-metals in the periodic system.
Atoms of non-metals have higher electronegativity values, and, accordingly, high ionization energies and high electron affinity. In this regard, the nature of non-metals is such that, unlike metals, they can exhibit oxidizing properties. In reactions, they can be restored by adding so many electrons that their total number at the outer level reaches eight (the completed level, the stable state of the atom).
That is why the negative value of the oxidation state that non-metals can have in compounds, unlike metals, is equal to the difference (8-N groups). Non-metals have the highest electronegativity, the position of which falls on the upper right corner in the Periodic Table, that is, the halogens fluorine and chlorine, as well as oxygen. It is these elements that can form ionic bonds. The most active non-metal is fluorine, which in compounds can exhibit only one valence I and one oxidation state -1.
The structural features of non-metals are that the outer electron layer of most non-metal atoms contains from 4 to 8 electrons.
Other non-metals (except fluorine) can also exhibit positive oxidation states, forming covalent bonds with other elements.
For most non-metals of simple substances in the solid state of aggregation, a molecular crystal lattice is characteristic. That is, these non-metals are crystalline substances. Therefore, under normal conditions, they have the form of gases, liquids or solids with low melting points. Examples of such substances are gases: hydrogen H 2, neon Ne, liquid - bromine Br 2, solids iodine I 2, sulfur S 8, phosphorus P 4 (white phosphorus). There are non-metals (boron, carbon, silicon) that have atomic crystal lattices.
Rice. 2. Non-metals - liquids, gases, solids.
The most important elements that are contained in living organisms are organogens. They form water, proteins, vitamins, fats. These include 6 elements: carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur.
Hydrogen compounds of non-metals are mainly volatile compounds, in aqueous solutions having an acidic character. They have molecular structures, a covalent polar bond. Some of them (water, ammonia, hydrogen fluoride) form hydrogen bonds. Compounds are formed by the direct interaction of non-metals with hydrogen. The electronic formula of sulfur with hydrogen is as follows:
S + H 2 \u003d H 2 S (up to 350 degrees, the balance is shifted to the right)
All hydrogen compounds are reducing agents (except HF), and their reducing power increases from right to left along the period and from top to bottom in the subgroup.
Nonmetals interact with metals and other nonmetals:
The result is sodium salt of hydrochloric acid
Rice. 3. sodium salt of hydrochloric acid.
compounds of non-metals with oxygen, as a rule, are acidic oxides, which correspond to oxygen-containing acids. The structure of oxides of typical non-metals is molecular (SO 3, P 4 O 10). The higher the oxidation state of the nonmetal, the stronger the corresponding oxoacid. So, chlorine does not directly interact with oxygen, but forms a number of oxo acids, which correspond to oxides, anhydrides of these acids.
Non-metals are used in various industries. Here is a list of industries where their use is most in demand.
| Application area | Examples, a list of non-metals used in a particular industry |
| industry | Sulfur, nitrogen and phosphorus are often used to produce acids. Sulfur is also used in the production of rubber. |
| transport | Hydrogen is an important non-metal in the transport industry. It is used as a fuel. When burned, this type of fuel does not pollute the environment. |
| agricultural industry | sulfur is used to fight harmful insects and plant diseases |
| the medicine | Oxygen is used to restore breathing ( oxygen bags), carbon in the form of activated carbon, which is able to remove harmful substances from the body. |
| food industry | nitrogen is used to extend the shelf life of products |
The position of non-metal elements in the Periodic system of chemical elements D.I. Mendeleev
Elements-non-metals:
s-element - hydrogen;
p-elements of the 3rd group - boron;
4 groups - carbon and silicon;
5 groups - nitrogen, phosphorus and arsenic,
6 groups - oxygen, sulfur, selenium and tellurium
7 groups - fluorine, chlorine, bromine, iodine and astatine.
Elements of the 8th group - inert gases, occupy a special position, they have a completely completed outer electron layer.
Non-metal chemical elements can exhibit both oxidizing and reducing properties, depending on the chemical transformation in which they take part.
The atoms of the most electronegative element - fluorine - are not able to donate electrons, it always exhibits only oxidizing properties, other elements can also exhibit reducing properties, although to a much lesser extent than metals. The most powerful oxidizing agents (accept electrons) are fluorine, oxygen and chlorine, hydrogen, boron, carbon, silicon, phosphorus, arsenic and tellurium exhibit predominantly reducing properties (give away). Intermediate redox properties have nitrogen, sulfur, iodine.
1. Interaction with metals:
2Na + Cl 2 = 2NaCl, Fe + S = FeS, 6Li + N 2 = 2Li 3 N, 2Ca + O 2 = 2CaO
in these cases, non-metals exhibit oxidizing properties, they accept electrons, forming negatively charged particles.
2. Interaction with other non-metals:
interacting with hydrogen , most non-metals exhibit oxidizing properties, forming volatile hydrogen compounds - covalent hydrides:
3H 2 + N 2 \u003d 2NH 3, H 2 + Br 2 \u003d 2HBr;
interacting with oxygen , all non-metals, except for fluorine, exhibit reducing properties:
S + O 2 \u003d SO 2, 4P + 5O 2 \u003d 2P 2 O 5;
when interacting with fluorine fluorine is an oxidizing agent, and oxygen is a reducing agent: 2F 2 + O 2 \u003d 2OF 2;
non-metals interact between themselves , a more electronegative metal plays the role of an oxidizing agent, a less electronegative one plays the role of a reducing agent: S + 3F 2 \u003d SF 6, C + 2Cl 2 \u003d CCl 4.
Halogens (Group 7)
Chemical properties of halogens.
OXYGEN-CONTAINING CHLORINE ACID
· Hypochlorous acid HCl +1 O salt - hypo chlorites
It exists only in the form of dilute aqueous solutions.
Obtaining Cl2 + H2O = HCl + HClO
Chemical properties
HClO is a weak acid and a strong oxidizing agent:
1) Decomposes in the light, releasing atomic oxygen HClO = HCl + O
2) With alkalis gives salts - hypochlorites HClO + KOH = KClO + H2O
3) Interacts with hydrogen halides 2HI + HClO = I2 + HCl + H2O
Chloric acid HClO2 (HClO2 is a weak acid and a strong oxidizing agent; salts of hydrochloric acid - chlorites)
Chemical properties
1.HClO2 + KOH = KClO2 + H2O
2. Unstable, decomposes during storage 4HClO2 = HCl + HClO3 + 2ClO2 + H2O
Perchloric acid HCl O3 (HClO3 - Strong acid and strong oxidizing agent; chloric acid salts - chlorates)
KClO 3 - Berthollet's salt; it is obtained by passing chlorine through a heated (40 ° C) KOH solution:
3Cl 2 + 6KOH \u003d 5KCl + KClO 3 + 3H 2 O
Berthollet's salt is used as an oxidizing agent; when heated, it decomposes:
4KClO 3 = KCl + 3KClO 4 (no catalyst)
2KClO 3 \u003d 2KCl + 3O 2 (MnO 2 catalyst)
Perchloric acid HClO4 (HClO4 is a very strong acid and a very strong oxidizing agent; perchloric acid salts - perchlorates)
Obtaining KClO4 + H2SO4 = KHSO4 + HClO4
Chemical properties
1) Interacts with alkalis HClO4 + KOH = KClO4 + H2O
2) When heated, perchloric acid and its salts decompose:
4HClO4 = 4ClO2 + 3O2 + 2H2O KClO4 = KCl + 2O2
Chalcogens (group VIA elements)
Oxygen, S, Se, Te, Po. The name chalcogens means "giving birth to ores". Sulfur compounds: pyrite, or iron pyrite - FeS2, cinnabar - HgS, zinc blende - ZnS.
At the outer energy level, chalcogens have 6 electrons. Before the completion of the external energy level, atoms lack 2 electrons, so they add electrons and show an oxidation state of -2 in their compounds.
Sulfur, selenium and tellurium atoms in their compounds with more electronegative elements exhibit positive oxidation states +2, +4 and +6.
Oxygen n=8 1s 2 2s 2 2p 4
Oxygen is part of such ores as corundum - Al2O3, magnetic iron ore - Fe3O4, red iron ore - Fe2O3, brown iron ore - Fe2O3
Oxygen combined with fluorine - OF2 exhibits an oxidation state of +2. Oxygen is part of the atmosphere, where it accounts for 21%.
Getting oxygen.
In industry, oxygen is obtained from liquid air.
Oxygen can also be obtained by decomposing water in a special device - an electrolyzer.
· Hydrogen peroxide (H2O2) is used in the laboratory. This reaction takes place in the presence of a catalyst - manganese oxide IV
In the laboratory, the decomposition reaction of potassium permanganate - KMnO 4 - "potassium permanganate" is also used.
In laboratory conditions, oxygen is released when berthollet salt (potassium chlorate) is heated
2KClO 3 \u003d 2KCl + 3O 2 The catalyst is manganese oxide (MnO 2).
oxygen exists in the form of two allotropic modifications - O 2 and O 3.
Chemical properties
Oxygen does not interact with halogens, noble gases, gold and platinum.
Oxygen reacts vigorously with metals. For example, in a reaction with lithium, lithium oxide is formed, in a reaction with copper, copper (II) oxide is formed.
4Li + O 2 \u003d 2Li 2 O 2Cu + O 2 \u003d 2CuO
· Oxygen reacts with non-metals.
S + O 2 \u003d SO 2 4P + 5O 2 \u003d 2P 2 O 5
Almost all reactions with oxygen are exothermic (that is, accompanied by the release of heat). An exception is the reaction of nitrogen with oxygen, which is endothermic.
N 2 + O 2 ↔ 2NO - Q
Oxygen is a complex substance.
CH 4 + 2O 2 \u003d CO 2 + 2H 2 O 2H 2 S + 3O 2 \u003d 2SO 2 + 2H 2 O
SULFUR n=16 1s 2 2s 2 2p 6 3s 2 3p 4
There are only 16 non-metal chemical elements, but two of them, oxygen and silicon, make up 76% of the mass of the earth's crust. Non-metals make up 98.5% of the mass of plants and 97.6% of the mass of a person. All the most important organic substances are composed of carbon, hydrogen, oxygen, sulfur, phosphorus and nitrogen; they are the elements of life. Hydrogen and helium are the main elements of the Universe, all space objects, including our Sun, consist of them. It is impossible to imagine our life without non-metal compounds, especially if we remember that the vital chemical compound - water - consists of hydrogen and oxygen.
If we draw a diagonal from beryllium to astatine in the Periodic system, then non-metal elements will be on the diagonal upwards to the right, and metals will be on the bottom left, they also include elements of all secondary subgroups, lanthanides and actinides. Elements located near the diagonal, for example, beryllium, aluminum, titanium, germanium, antimony, have a dual character and are metalloids. Non-metal elements: s-element - hydrogen; p-elements of group 13 - boron; 14 groups - carbon and silicon; 15 groups - nitrogen, phosphorus and arsenic, 16 groups - oxygen, sulfur, selenium and tellurium and all elements of group 17 - fluorine, chlorine, bromine, iodine and astatine. Elements of group 18 - inert gases, occupy a special position, they have a completely completed outer electron layer and occupy an intermediate position between metals and non-metals. They are sometimes referred to as non-metals, but formally, according to physical characteristics.
non-metals- these are chemical elements whose atoms accept electrons to complete the external energy level, thus forming negatively charged ions.
In the outer electron layer of non-metal atoms, there are from three to eight electrons.
Almost all non-metals have relatively small radii and a large number of electrons in the external energy level from 4 to 7, they are characterized by high electronegativity and oxidizing properties. Therefore, compared with metal atoms, non-metals are characterized by:
smaller atomic radius;
four or more electrons in the outer energy level;
Hence this the most important property atoms of non-metals - a tendency to receive missing up to 8 electrons, i.e. oxidizing properties. Qualitative characteristic non-metal atoms, i.e. a kind of measure of their non-metallicity, can serve as electronegativity, i.e. the property of atoms of chemical elements to polarize a chemical bond, to attract common electron pairs;
The very first scientific classification of chemical elements was their division into metals and non-metals. This classification has not lost its significance at the present time. Non-metals are chemical elements whose atoms are characterized by the ability to accept electrons before the completion of the outer layer due to the presence, as a rule, of four or more electrons on the outer electron layer and the small radius of atoms compared to metal atoms.
This definition leaves aside the elements of group VIII of the main subgroup - inert, or noble, gases, the atoms of which have a completed outer electron layer. The electronic configuration of the atoms of these elements is such that they cannot be attributed to either metals or non-metals. They are those objects that separate elements into metals and non-metals, occupying a boundary position between them. Inert, or noble, gases ("nobility" is expressed in inertia) are sometimes referred to as non-metals, but only formally, according to physical characteristics. These substances retain their gaseous state down to very low temperatures. Thus, helium does not go into a liquid state at t° = -268.9°C.
The chemical inertness of these elements is relative. For xenon and krypton, compounds with fluorine and oxygen are known: KrF 2 , XeF 2 , XeF 4 and others. Undoubtedly, in the formation of these compounds, inert gases acted as reducing agents. From the definition of non-metals, it follows that their atoms are characterized by high values of electronegativity. It varies from 2 to 4. Non-metals are elements of the main subgroups, mainly p-elements, with the exception of hydrogen - an s-element.
All non-metal elements (except hydrogen) occupy the upper right corner in the Periodic Table of Chemical Elements of D. I. Mendeleev, forming a triangle, the apex of which is fluorine F, and the base is the diagonal B - At. However, special attention should be paid to the dual position of hydrogen in the Periodic system: in the main subgroups of groups I and VII. This is no coincidence. On the one hand, the hydrogen atom, like alkali metal atoms, has one electron on the outer (and the only one for it) electron layer (electronic configuration 1s 1), which it is able to donate, showing the properties of a reducing agent.
In most of its compounds, hydrogen, like the alkali metals, exhibits an oxidation state of +1. But the release of an electron by a hydrogen atom is more difficult than that of alkali metal atoms. On the other hand, the hydrogen atom, like the halogen atoms, lacks one electron to complete the outer electron layer, so the hydrogen atom can accept one electron, showing the properties of an oxidizing agent and the oxidation state characteristic of the halogen -1 in hydrides (compounds with metals, similar to metal compounds with halogens - halides). But the attachment of one electron to a hydrogen atom is more difficult than with halogens.
Under normal conditions, hydrogen H 2 is a gas. Its molecule, like halogens, is diatomic. The atoms of non-metals are dominated by oxidizing properties, i.e., the ability to attach electrons. This ability characterizes the value of electronegativity, which naturally changes in periods and subgroups. Fluorine is the strongest oxidizing agent, its atoms in chemical reactions are not able to donate electrons, i.e., exhibit reducing properties. Other non-metals can exhibit reducing properties, although to a much weaker extent compared to metals; in periods and subgroups, their reducing ability changes in the reverse order compared to the oxidizing one.
In simple substances, non-metal atoms are bonded covalent non-polar bond. Due to this, a more stable electronic system is formed than that of isolated atoms. In this case, single (for example, in hydrogen molecules H 2, halogens F 2, Br 2, I 2), double (for example, in sulfur molecules S 2), triple (for example, in nitrogen molecules N 2) covalent bonds are formed.
State of aggregation:
Unlike metals, non-metals are simple substances, characterized by a wide variety of properties. Non-metals have a different state of aggregation under normal conditions:
Non-metals also have a much richer spectrum of colors: red - for phosphorus, red-brown - for bromine, yellow - for sulfur, yellow-green - for chlorine, violet - for iodine vapor. Elements - non-metals are more capable, in comparison with metals, of allotropy.
The ability of atoms of one chemical element to form several simple substances is called allotropy, and these simple substances are called allotropic modifications.
Simple substances - non-metals can have:
1. Molecular structure. Under normal conditions, most of these substances are gases (H 2, N 2, O 2, F 2, Cl 2, O 3) or solids (I 2, P 4, S 8), and only one single bromine (Br 2) is a liquid. All these substances have a molecular structure, therefore they are volatile. In the solid state, they are fusible due to the weak intermolecular interaction that keeps their molecules in the crystal, and are capable of sublimation.
2. Atomic structure. These substances are formed by long chains of atoms (C n , B n , Si n , Se n , Te n). Due to the high strength of covalent bonds, they, as a rule, have high hardness, and any changes associated with the destruction of the covalent bond in their crystals (melting, evaporation) are performed with a large expenditure of energy. Many of these substances have high melting and boiling points, and their volatility is very low.
Many non-metal elements form several simple substances - allotropic modifications. This property of atoms is called allotropy. Allotropy can also be associated with a different composition of molecules (O 2, O 3), and with a different structure of crystals. Allotropic modifications of carbon are graphite, diamond, carbine, fullerene. To reveal the properties characteristic of all non-metals, it is necessary to pay attention to their location in the periodic system of elements and determine the configuration of the outer electronic layer.
In the period:
In the main subgroup:
Most metals, with rare exceptions (gold, copper, and some others), are characterized by a silvery-white color. But for simple substances - non-metals, the range of colors is much more diverse: P, Se - yellow; B - brown; O 2 (g) - blue; Si, As (met) - gray; P 4 - pale yellow; I - purple-black with a metallic sheen; Br 2(g) - brown liquid; C1 2(d) - yellow-green; F 2 (r) - pale green; S 8 (tv) - yellow. Non-metal crystals are non-plastic, and any deformation causes the destruction of covalent bonds. Most non-metals do not have a metallic sheen.
There are only 16 chemical elements-non-metals! Quite a bit, considering that 114 elements are known. Two non-metal elements make up 76% of the mass of the earth's crust. These are oxygen (49%) and silicon (27%). The atmosphere contains 0.03% of the mass of oxygen in the earth's crust. Non-metals make up 98.5% of the mass of plants, 97.6% of the mass of the human body. Non-metals C, H, O, N, S are biogenic elements that form the most important organic substances of a living cell: proteins, fats, carbohydrates, nucleic acids. The composition of the air we breathe includes simple and complex substances, also formed by non-metal elements (oxygen O 2, nitrogen N 2, carbon dioxide CO 2, water vapor H 2 O, etc.)
For atoms of non-metals, and consequently, for the simple substances formed by them, they are characterized as oxidative, and restorative properties.
1. Oxidizing properties of non-metals appear first when interacting with metals(metals are always reducing agents):
The oxidizing properties of chlorine Cl 2 are more pronounced than those of sulfur, therefore, the Fe metal, which has stable oxidation states of +2 and +3 in compounds, is oxidized by it to a higher oxidation state.
1. Most non-metals exhibit oxidizing properties when interacting with hydrogen. As a result, volatile hydrogen compounds are formed.
2. Any non-metal acts as an oxidizing agent in reactions with those non-metals that have a lower electronegativity value:
The electronegativity of sulfur is greater than that of phosphorus, so it exhibits oxidizing properties here.
The electronegativity of fluorine is greater than that of all other chemical elements, so it exhibits the properties of an oxidizing agent. Fluorine F 2 is the strongest non-metal oxidizing agent, it exhibits only oxidizing properties in reactions.
3. Non-metals also exhibit oxidizing properties in reactions with some complex substances..
First of all, we note the oxidizing properties of the non-metal oxygen in reactions with complex substances:
Not only oxygen, but also other non-metals can also be oxidizing agents in reactions with complex substances.- inorganic (1, 2) and organic (3, 4):
The strong oxidizing agent chlorine Cl 2 oxidizes iron (II) chloride to iron (III) chloride;
Chlorine Cl 2 as a stronger oxidizing agent displaces free iodine I 2 from a solution of potassium iodide;
Methane halogenation is a characteristic reaction for alkanes;
A qualitative reaction to unsaturated compounds is their discoloration of bromine water.
By revising reactions of non-metals with each other that, depending on the value of their electronegativity, one of them exhibits the properties of an oxidizing agent, and the other - the properties of a reducing agent.
1. In relation to fluorine, all non-metals (even oxygen) exhibit reducing properties.
2. Of course, non-metals, except for fluorine, serve as reducing agents when interacting with oxygen.
As a result of the reactions, non-metal oxides: non-salt-forming and salt-forming acid. And although halogens do not combine directly with oxygen, their oxides are known: Cl 2 +1 O -2, Cl 2 +4 O 2 -2, Cl 2 +7 O 7 -2, Br 2 +1 O -2, Br +4 O 2 -2, I 2 +5 O 5 -2, etc., which are obtained indirectly.
3. Many non-metals can act as a reducing agent in reactions with complex substances - oxidizing agents:
There are also reactions in which the same non-metal is both an oxidizing agent and a reducing agent. These are autoxidation-self-healing (disproportionation) reactions:
Thus, most non-metals can act in chemical reactions both as an oxidizing agent and as a reducing agent (reductive properties are not inherent only in fluorine F 2).
Unlike metals, non-metals form gaseous hydrogen compounds. Their composition depends on the degree of oxidation of non-metals.
RH 4 → RH 3 → H 2 R → HR
Common property of all non-metals is the formation of volatile hydrogen compounds, in most of which the non-metal has the lowest oxidation state. Among the given formulas of substances, there are many those whose properties, application and preparation you studied earlier: CH 4, NH 3, H 2 O, H 2 S, HCl.
It is known that these compounds can be obtained most simply directly. interaction of a non-metal with hydrogen, that is, by synthesizing:
All hydrogen compounds of non-metals are formed by covalent polar bonds, have a molecular structure and under normal conditions are gases, except for water (liquid). Hydrogen compounds of nonmetals are characterized by different attitude to the water. Methane and silane are practically insoluble in it. Ammonia, when dissolved in water, forms a weak base NH 3 H 2 O. When hydrogen sulfide, hydrogen selenide, hydrogen telluride, and hydrogen halides are dissolved in water, acids are formed with the same formula as the hydrogen compounds themselves: H 2 S, H 2 Se, H 2 Te, HF, HCl, HBr, HI.
If we compare the acid-base properties of hydrogen compounds formed by non-metals of one period, for example, the second (NH 3, H 2 O, HF) or the third (PH 3, H 2 S, HCl), then we can conclude that their acidic properties naturally increase and, accordingly, the weakening of the main ones. This is obviously due to the fact that the polarity increases E-N communications(where E is a non-metal).
The acid-base properties of hydrogen compounds of non-metals of the same subgroup also differ. For example, in the series of hydrogen halides HF, HCl, HBr, HI, the strength of the E-H bond decreases, since the bond length increases. In solutions of HCl, HBr, HI dissociate almost completely - these are strong acids, and their strength increases from HF to HI. At the same time, HF refers to weak acids, which is due to another factor - intermolecular interaction, the formation of hydrogen bonds …H-F…H-F… . Hydrogen atoms are bonded to fluorine atoms F not only of their own molecule, but also of the neighboring one.
Summarizing the comparative characteristics of the acid-base properties of hydrogen compounds of non-metals, we conclude that the acidic and weakening of the basic properties of these substances are enhanced by periods and main subgroups with an increase in the atomic numbers of the elements that form them.
According to the period in the PS of chemical elements, with an increase in the serial number of the element - non-metal, the acidic nature of the hydrogen compound increases.
SiH 4 → PH 3 → H 2 S → HCl
In addition to the considered properties, hydrogen compounds of non-metals in redox reactions always exhibit the properties of reducing agents, because in them the non-metal has the lowest oxidation state.
Hydrogen is the main element of the Universe. Many space objects (gas clouds, stars, including the Sun) are more than half made up of hydrogen. On Earth, it, including the atmosphere, hydrosphere and lithosphere, is only 0.88%. But this is by mass, and the atomic mass of hydrogen is very small. Therefore, its small content is only apparent, and out of every 100 atoms on Earth, 17 are hydrogen atoms.
In the free state, hydrogen exists in the form of H 2 molecules, the atoms are bound into a molecule covalent non-polar bond.
Hydrogen (H 2) is the lightest of all gaseous substances. It has the highest thermal conductivity and the lowest boiling point (after helium). Slightly soluble in water. At a temperature of -252.8 °C and atmospheric pressure, hydrogen passes into a liquid state.
1. The hydrogen molecule is very strong, which makes it inactive:
H 2 \u003d 2H - 432 kJ
2. At ordinary temperatures, hydrogen reacts with active metals:
Ca + H 2 \u003d CaH 2,
forming calcium hydride, and with F 2, forming hydrogen fluoride:
F 2 + H 2 \u003d 2HF
3. At high temperatures get ammonia:
and titanium hydride (metal in powder):
4. When ignited, hydrogen reacts with oxygen:
5. Hydrogen has a restorative ability:
Elements of the main subgroup of group VII of the periodic system, united under a common name halogens, fluorine (F), chlorine (Cl), bromine (Bg), iodine (I), astatine (At) (rarely found in nature) are typical non-metals. This is understandable, because their atoms contain outer energy level has seven electrons, and they only need one electron to complete it. The atoms of these elements, when interacting with metals, accept an electron from metal atoms. This gives rise to ionic bond and salts are formed. Hence the common name "halogens", i.e. "giving birth to salts."
very strong oxidizers. Fluorine in chemical reactions exhibits only oxidizing properties, and it is characterized by an oxidation state of -1. The remaining halogens can also exhibit reducing properties when interacting with more electronegative elements - fluorine, oxygen, nitrogen, while their oxidation states can take on the values +1, +3, +5, +7. The reducing properties of halogens increase from chlorine to iodine, which is associated with an increase in the radii of their atoms: there are about half as many chlorine atoms as those of iodine.
All halogens exist in the free state as diatomic molecules with a covalent non-polar chemical bond between the atoms. In the solid state, F 2, Cl 2, Br 2, I 2 have molecular crystal lattices, which is confirmed by their physical properties.
With the increase molecular weight halogens, the melting and boiling points increase, the density increases: bromine is a liquid, iodine is solid, fluorine and chlorine gases. This is due to the fact that with an increase in the size of atoms and molecules of halogens, the forces of intermolecular interaction between them increase. From F 2 to I 2, the color intensity of the halogens increases.
The chemical activity of halogens, as non-metals, weakens from fluorine to iodine, the iodine crystals have a metallic sheen. Each halogen is the strongest oxidizing agent in its period.. The oxidizing properties of halogens are clearly manifested when they interact with metals. This forms salts. So, fluorine already under normal conditions reacts with most metals, and when heated, with gold, silver, platinum, known for their chemical passivity. Aluminum and zinc ignite in a fluorine atmosphere:
Other halogens react with metals when heated.. Heated iron powder also ignites when interacting with chlorine. The experiment can be carried out as with antimony, but only iron filings must first be heated in an iron spoon, and then poured out in small portions in a flask with chlorine. Since chlorine is a strong oxidizing agent, iron (III) chloride is formed as a result of the reaction:
In bromine vapor burning hot copper wire:
Iodine oxidizes metals more slowly, but in the presence of water, which is a catalyst, the reaction of iodine with aluminum powder proceeds very rapidly:
The reaction is accompanied by the evolution of violet vapors of iodine.
On the decrease in oxidizing and increasing the reducing properties of halogens from fluorine to iodine can be judged by their ability to displace each other from solutions of their salts, and it is also clearly manifested when they interact with hydrogen. The equation for this reaction can be written as general view So:
If fluorine interacts with hydrogen under any conditions with an explosion, then a mixture of chlorine and hydrogen reacts only when ignited or irradiated with direct sunlight, bromine interacts with hydrogen when heated and without an explosion. These reactions are exothermic. The reaction of the combination of iodine with hydrogen is weakly endothermic, it proceeds slowly even when heated.
As a result of these reactions, hydrogen fluoride HF, hydrogen chloride HCl, hydrogen bromide HBr and hydrogen iodine HI are formed, respectively.
Chemical properties of chlorine in tables
Fluorine and chlorine are obtained by electrolysis of melts or solutions of their salts. For example, the process of electrolysis of a sodium chloride melt can be reflected by the equation:
When chlorine is obtained by electrolysis of a sodium chloride solution, in addition to chlorine, hydrogen and sodium hydroxide are also formed:
Oxygen (O)- the ancestor of the main subgroup of group VI of the Periodic system of elements. The elements of this subgroup - oxygen O, sulfur S, selenium Se, tellurium Te, polonium Po - have the common name "chalcogens", which means "giving birth to ores".
Oxygen is the most abundant element on our planet. It is part of the water (88.9%), and yet it covers 2/3 of the surface of the globe, forming its water shell - the hydrosphere. Oxygen is second in quantity and first in importance for life. component the air shell of the Earth - the atmosphere, where it accounts for 21% (by volume) and 23.15% (by mass). Oxygen is part of numerous minerals in the hard shell of the earth's crust - the lithosphere: out of every 100 atoms of the earth's crust, 58 atoms fall to the share of oxygen.
Ordinary oxygen exists in the form of O 2 . It is a colorless, odorless and tasteless gas. In the liquid state it has a light blue color, in the solid state it is blue. Gaseous oxygen is more soluble in water than nitrogen and hydrogen.
Oxygen interacts with almost all simple substances, except halogens, noble gases, gold and platinum metals. The reactions of non-metals with oxygen proceed very often with the release a large number heat and are accompanied by ignition - combustion reactions. For example, the combustion of sulfur with the formation of SO 2, phosphorus - with the formation of P 2 O 5 or coal - with the formation of CO 2. Almost all reactions involving oxygen are exothermic. An exception is the interaction of nitrogen with oxygen: this is an endothermic reaction that occurs at temperatures above 1200 ° C or during an electric discharge:
Oxygen vigorously oxidizes not only simple, but also many complex substances, while oxides of the elements from which they are built are formed:
The high oxidizing power of oxygen underlies the combustion of all fuels.
Oxygen is also involved in the processes of slow oxidation of various substances at ordinary temperatures. The role of oxygen in the process of respiration of humans and animals is extremely important. Plants also absorb atmospheric oxygen. But if only the process of oxygen absorption by plants takes place in the dark, then another opposite process proceeds in the light - photosynthesis, as a result of which plants absorb carbon dioxide and release oxygen.
In industry, oxygen is obtained from liquid air, and in the laboratory - by decomposition of hydrogen peroxide in the presence of manganese dioxide catalyst MnO 2 :
as well as decomposition of potassium permanganate KMnO 4 when heated:
Chemical properties of oxygen in tables
Oxygen is used in the metallurgical and chemical industries to accelerate (intensify) production processes. Pure oxygen is also used to obtain high temperatures, for example, in gas welding and metal cutting. In medicine, oxygen is used in cases of temporary difficulty in breathing associated with certain diseases. Oxygen is also used in metallurgy as an oxidizing agent for rocket fuel, in aviation for breathing, for cutting metals, for welding metals, and during blasting. Oxygen is stored in blue-painted steel cylinders at a pressure of 150 atm. Under laboratory conditions, oxygen is stored in glass devices - gasometers.
atoms sulfur (S), like the atoms of oxygen and all other elements of the main subgroup of group VI, contain on the external energy level 6 electrons, of which two unpaired electrons. However, compared with oxygen atoms, sulfur atoms have a larger radius, a lower electronegativity value, therefore, they exhibit pronounced reducing properties, forming compounds with oxidation states +2, +4, +6. In relation to less negative elements (hydrogen, metals), sulfur exhibits oxidizing properties and acquires an oxidation state -2 .
Sulfur, like oxygen, is characterized by allotropy. There are many modifications of sulfur with a cyclic or linear structure of molecules of various compositions.
The most stable modification is known as rhombic sulfur, consisting of S 8 molecules. Its crystals look like octahedrons with cut corners. They are lemon yellow and translucent, melting point 112.8 °C. All other modifications are converted into this modification at room temperature. During crystallization from the melt, monoclinic sulfur is first obtained (acicular crystals, melting point 119.3 ° C), which then passes into rhombic sulfur. When sulfur pieces are heated in a test tube, it melts, turning into a liquid. yellow color. At a temperature of about 160 ° C, liquid sulfur begins to darken, becomes thick and viscous, does not pour out of the test tube, and upon further heating turns into a highly mobile liquid, but retains its former dark brown color. If poured into cold water, it solidifies in the form of a transparent rubbery mass. This is plastic sulfur. It can also be obtained in the form of threads. After a few days, it also turns into rhombic sulfur.
Sulfur does not dissolve in water. Sulfur crystals sink in water, but the powder floats on the surface of the water, because small sulfur crystals are not wetted by water and are kept afloat by small air bubbles. This is the flotation process. Sulfur is sparingly soluble in ethyl alcohol and diethyl ether, it is readily soluble in carbon disulfide.
Under normal conditions sulfur reacts with all alkali and alkaline earth metals, copper, mercury, silver, eg:
This reaction underlies the removal and neutralization of spilled mercury, for example, from a broken thermometer. Visible droplets of mercury can be collected on a piece of paper or copper plastic. The mercury that got into the cracks must be covered with sulfur powder. This process is called demercurization.
When heated, sulfur also reacts with other metals (Zn, Al, Fe), and only gold does not interact with it under any conditions. Sulfur also exhibits oxidizing properties with hydrogen, with which it reacts when heated:
Of the non-metals, only nitrogen, iodine and noble gases do not react with sulfur. Sulfur burns with a bluish flame, forming sulfur oxide (IV):
This compound is commonly known as sulfur dioxide.
Chemical properties of sulfur in tables
Sulfur is one of the most common elements: the earth's crust contains 4.7 10-2% sulfur by mass (15th place among other elements), and the Earth as a whole is much more (0.7%). The main mass of sulfur is found in the depths of the earth, in its mantle layer, located between the earth's crust and the earth's core. Here, at a depth of about 1200-3000 km, there is a thick layer of sulfides and metal oxides. In the earth's crust, sulfur occurs both in the free state (native), and mainly in the form of compounds of sulfides and sulfates. Of the sulfides in the earth's crust, the most common are pyrite FeS2, chalcopyrite FeCuS2, lead luster (galena) PbS, zinc blende (sphalerite) ZnS. Large quantities sulfurs are found in the earth's crust in the form of sparingly soluble sulfates - gypsum CaSO4 2H2O, barite BaSO4, magnesium, sodium and potassium sulfates are common in sea water.
It is interesting that in ancient times of the geological history of the Earth (about 800 million years ago) there were no sulfates in nature. They were formed as products of the oxidation of sulfides when an oxygen atmosphere appeared as a result of the vital activity of plants. Hydrogen sulfide H2S and sulfur dioxide SO2 are found in volcanic gases. therefore, native sulfur found in areas close to active volcanoes (Sicily, Japan) could be formed by the interaction of these two gases:
2H 2 S + SO 2 \u003d 3S + 2H 2 O.
Other deposits of native sulfur are associated with the vital activity of microorganisms.
Microorganisms are involved in many chemical processes, which generally make up the sulfur cycle in nature. With their assistance, sulfides are oxidized to sulfates, sulfates are absorbed by living organisms, where sulfur is reduced and is part of proteins and other vital substances. When the dead remains of organisms rot, proteins are destroyed, and hydrogen sulfide is released, which is then oxidized either to elemental sulfur (this is how sulfur deposits are formed) or to sulfates. Interestingly, bacteria and algae that oxidize hydrogen sulfide to sulfur collect it in their cells. The cells of such microorganisms can be 95% pure sulfur.
The origin of sulfur can be determined by the presence of its analogue, selenium: if selenium is found in native sulfur, then sulfur is of volcanic origin, if not, of biogenic origin, since microorganisms avoid including selenium in their life cycle, and biogenic sulfur also contains more the heavier 34S.
Vital chemical element. It is part of proteins - one of the main chemical components of the cells of all living organisms. Especially a lot of sulfur in the proteins of hair, horns, wool. In addition, sulfur is an integral part of the biologically active substances of the body: vitamins and hormones (for example, insulin). Sulfur is involved in the redox processes of the body. With a lack of sulfur in the body, fragility and fragility of bones and hair loss are observed.
Sulfur is rich in legumes (peas, lentils), oatmeal, eggs.
Sulfur is used in the manufacture of matches and paper, rubber and paint, explosives and drugs, plastics and cosmetics. In agriculture, it is used to control plant pests. However, the main consumer of sulfur is the chemical industry. About half of the sulfur produced in the world goes to the production of sulfuric acid.
Nitrogen (N)- the first representative of the main subgroup of group V of the Periodic system. Its atoms contain five electrons at the outer energy level, of which three electrons are unpaired. It follows that the atoms of these elements can add three electrons, completing the outer energy level.
Nitrogen atoms can donate their outer electrons to more electronegative elements (fluorine, oxygen) and acquire oxidation states +3 and +5. Nitrogen atoms also exhibit reducing properties in oxidation states +1, +2, +4.
In the free state, nitrogen exists in water of the diatomic molecule N 2 . In this molecule, two N atoms are linked by a very strong triple covalent bond, these bonds can be denoted as follows:
Nitrogen is a colorless, odorless and tasteless gas.
Under normal conditions nitrogen interacts only with lithium, forming Li nitride 3 N:
It interacts with other metals only at high temperatures.
Also at high temperatures and pressures in the presence of a catalyst, nitrogen reacts with hydrogen to form ammonia:
At a temperature electric arc it combines with oxygen to form nitric oxide (II):
Chemical properties of nitrogen in tables
Nitrogen obtained by distillation of liquid air is used in industry for the synthesis of ammonia and the production of nitric acid. In medicine, pure nitrogen is used as an inert medium for the treatment of pulmonary tuberculosis, and liquid nitrogen is used in the treatment of diseases of the spine, joints, etc.
The chemical element phosphorus forms several allotropic modifications. Two of them are simple substances: white phosphorus and red phosphorus. White phosphorus has a molecular crystal lattice consisting of P 4 molecules. Insoluble in water, readily soluble in carbon disulfide. It oxidizes easily in air, and even ignites in a powdered state. White phosphorus is highly toxic. special property is the ability to glow in the dark due to oxidation. Store it under water. Red phosphorus is a dark crimson powder. It does not dissolve in water or carbon disulfide. It oxidizes slowly in air and does not ignite spontaneously. Non-poisonous and does not glow in the dark. When red phosphorus is heated in a test tube, it turns into white phosphorus (concentrated vapors).
The chemical properties of red and white phosphorus are similar, but white phosphorus is more chemically active. So, both of them interact with metals, forming phosphides:
White phosphorus ignites spontaneously in air, while red phosphorus burns when ignited. In both cases, phosphorus oxide (V) is formed, which is released in the form of thick white smoke:
Phosphorus does not directly react with hydrogen, phosphine PH 3 can be obtained indirectly, for example, from phosphides:
Phosphine is a highly toxic gas bad smell. Easily ignites in air. This property of phosphine explains the appearance of swamp wandering lights.
Chemical properties of phosphorus in tables
Phosphorus is the most important biogenic element and at the same time is very widely used in industry. Red phosphorus is used in the manufacture of matches. It, together with finely ground glass and glue, is applied to side surface boxes. When a match head is rubbed, which includes potassium chlorate and sulfur, ignition occurs.
Perhaps the first property of phosphorus, which man put to his service, is flammability. The combustibility of phosphorus is very high and depends on the allotropic modification.
White ("yellow") phosphorus is the most chemically active, toxic and flammable, and therefore it is very often used (in incendiary bombs, etc.).
Red phosphorus is the main modification produced and consumed by industry. It is used in the manufacture of matches, explosives, incendiary compositions, various types of fuels, as well as extreme pressure lubricants, as a getter in the manufacture of incandescent lamps.
Phosphorus (in the form of phosphates) is one of the three most important biogenic elements involved in the synthesis of ATP. Most of the phosphoric acid produced is used to obtain phosphate fertilizers - superphosphate, precipitate, ammophoska, etc.
Phosphates are widely used:
The ability of phosphates to form a strong three-dimensional polymer mesh used for the manufacture of phosphate and aluminophosphate binders.
Carbon (C)- the first element of the main subgroup of group VI of the Periodic system. Its atoms contain 4 electrons at the outer level, so they can accept four electrons, while acquiring an oxidation state -4 , i.e., exhibit oxidizing properties and donate their electrons to more electronegative elements, i.e., exhibit reducing properties, while acquiring an oxidation state +4.
Carbon forms allotropic modifications diamond and graphite. Diamond is a transparent crystalline substance, the hardest of all natural substances. It serves as a standard of hardness, which, according to a ten-point system, is estimated at the highest score of 10. Such hardness of diamond is due to the special structure of its atomic crystal lattice. In it, each carbon atom is surrounded by the same atoms located at the vertices of a regular tetrahedron.
Diamond crystals are usually colorless, but come in blue, blue, red, and black. They have a very strong luster due to their high light refraction and light reflectivity. And due to their exceptionally high hardness, they are used for the manufacture of drills, drills, grinding tools, glass cutting.
The largest diamond deposits are located in South Africa, and in Russia they are mined in Yakutia.
Graphite is a dark gray, greasy to the touch crystalline substance with a metallic sheen. Unlike diamond, graphite is soft (leaves a mark on paper) and opaque, it conducts heat and electric current well. The softness of graphite is due to the layered structure. In the crystal lattice of graphite, carbon atoms lying in the same plane are firmly bound into regular hexagons. The bonds between the layers are weak. He is very tough. Graphite is used to make electrodes, solid lubricants, neutron moderators in nuclear reactors, and pencil leads. At high temperatures and pressure, artificial diamonds are obtained from graphite, which are widely used in technology.
Soot and charcoal have a structure similar to graphite. Charcoal is obtained by dry distillation of wood. This coal, due to its porous surface, has a remarkable ability to absorb gases and dissolved substances. This property is called adsorption. The greater the porosity of the charcoal, the more efficient the adsorption. To increase the absorption capacity, charcoal treated with hot steam. The carbon processed in this way is called activated or active. In pharmacies, it is sold in the form of black tablets of carbolene.
Diamond and graphite combine with oxygen at very high temperatures. Soot and coal interact with oxygen much more easily, burning in it. But in any case, the result of such an interaction is the same - carbon dioxide is formed:
When heated with metals, carbon forms carbides:
aluminum carbide- light yellow transparent crystals. Known calcium carbide CaC 2 in the form of pieces gray color. It is used by gas welders to produce acetylene:
Acetylene used for cutting and welding metals, burning it with oxygen in special burners.
If you act on aluminum carbide with water, you get another gas - methane CH 4 :
Silicon (Si) is the second element of the main subgroup of group IV of the periodic system. In nature, silicon is the second most abundant chemical element after oxygen. Earth's crust more than a quarter consists of its compounds. The most common silicon compound is its dioxide SiO 2 - silica. In nature, it forms the mineral quartz and many varieties, such as rock crystal and its famous purple form - amethyst, as well as agate, opal, jasper, chalcedony, carnelian. Silicon dioxide is also common and quartz sand. The second type of natural silicon compounds are silicates. Among them, the most common aluminosilicates are granite, different kinds clay, mica. An aluminium-free silicate is, for example, asbestos. Silicon oxide is essential for plant and animal life. It gives strength to the stems of plants and the protective covers of animals. Silicon gives smoothness and strength to human bones. Silicon is part of the lower living organisms - diatoms and radiolarians.
Silicon burns in oxygen forming silicon dioxide or silicon (IV) oxide:
Being a non-metal, when heated, it combines with metals to form silicides:
Silicides are easily decomposed by water or acids, and a gaseous hydrogen compound of silicon is released - silane:
4HCl + Mg 2 Si → SiH 4 + 2MgCl 2
Unlike hydrocarbons, silane ignites spontaneously in air. and burns to form silicon dioxide and water:
The increased reactivity of silane compared to methane CH 4 is explained by the fact that silicon larger size atom than that of carbon, so the Si-H chemical bonds are weaker than the C-H bonds.
Silicon interacts with concentrated aqueous solutions of alkali, forming silicates and hydrogen:
Silicon is obtained by restoring it from magnesium dioxide or carbon:
Silicon oxide (IV), or silicon dioxide, or silica SiO 2, like CO 2, is an acid oxide. However, unlike CO 2, it has not a molecular, but an atomic crystal lattice. Therefore, SiO 2 is a solid and refractory substance. It does not dissolve in water and acids, except hydrofluoric, but interacts at high temperatures with alkalis to form salts of silicic acid - silicates:
Silicates can also be obtained by fusing silicon dioxide with metal oxides or carbonates:
Silicates of sodium and potassium are called soluble glass. Their aqueous solutions are the well-known silicate glue. From solutions of silicates by the action of stronger acids on them - hydrochloric, sulfuric, acetic and even carbonic - silicic acid is obtained H 2 SiO 3 :
Consequently, H 2 SiO 3 - very weak acid. It is insoluble in water and precipitates from the reaction mixture in the form of a gelatinous precipitate, sometimes compactly filling the entire volume of the solution, turning it into a semi-solid mass, similar to jelly, jelly. When this mass dries, a highly porous substance is formed - silica gel, which is widely used as an adsorbent - an absorber of other substances.
Reference material for passing the test:
Mendeleev table
Solubility table
