Due to the presence of free electrons (“electron gas”) in the crystal lattice, all metals exhibit the following characteristic general properties:

1) Plastic- the ability to easily change shape, stretch into a wire, roll into thin sheets.

2) metallic luster and opacity. This is due to the interaction of free electrons with light incident on the metal.

3) Electrical conductivity. It is explained by the directed movement of free electrons from the negative to the positive pole under the influence of a small potential difference. When heated, the electrical conductivity decreases, because. as the temperature rises, the vibrations of atoms and ions in the nodes of the crystal lattice increase, which makes it difficult for the directed movement of the “electron gas”.

4) Thermal conductivity. It is due to the high mobility of free electrons, due to which the temperature is quickly equalized by the mass of the metal. The highest thermal conductivity is in bismuth and mercury.

5) Hardness. The hardest is chrome (cuts glass); the softest - alkali metals - potassium, sodium, rubidium and cesium - are cut with a knife.

6) Density. It is less the less atomic mass metal and larger atomic radius. The lightest is lithium (ρ=0.53 g/cm3); the heaviest is osmium (ρ=22.6 g/cm3). Metals having a density less than 5 g/cm3 are considered "light metals".

7) Melting and boiling points. The most fusible metal is mercury (m.p. = -39°C), the most refractory metal is tungsten (t°m. = 3390°C). Metals with t°pl. above 1000°C are considered refractory, below - low melting point.

General chemical properties of metals

Strong reducing agents: Me 0 – nē → Me n +

A series of voltages characterizes the comparative activity of metals in redox reactions in aqueous solutions.

1. Reactions of metals with non-metals

1) With oxygen:
2Mg + O 2 → 2MgO

2) With sulfur:
Hg + S → HgS

3) With halogens:
Ni + Cl 2 – t° → NiCl 2

4) With nitrogen:
3Ca + N 2 – t° → Ca 3 N 2

5) With phosphorus:
3Ca + 2P – t° → Ca 3 P 2

6) With hydrogen (only alkali and alkaline earth metals react):
2Li + H 2 → 2LiH

Ca + H 2 → CaH 2

2. Reactions of metals with acids

1) Metals standing in the electrochemical series of voltages up to H reduce non-oxidizing acids to hydrogen:

Mg + 2HCl → MgCl 2 + H 2

2Al+ 6HCl → 2AlCl 3 + 3H 2

6Na + 2H 3 PO 4 → 2Na 3 PO 4 + 3H 2

2) With oxidizing acids:

In the interaction of nitric acid of any concentration and concentrated sulfuric acid with metals hydrogen is never released!

Zn + 2H 2 SO 4 (K) → ZnSO 4 + SO 2 + 2H 2 O

4Zn + 5H 2 SO 4(K) → 4ZnSO 4 + H 2 S + 4H 2 O

3Zn + 4H 2 SO 4(K) → 3ZnSO 4 + S + 4H 2 O

2H 2 SO 4 (c) + Cu → Cu SO 4 + SO 2 + 2H 2 O

10HNO 3 + 4Mg → 4Mg(NO 3) 2 + NH 4 NO 3 + 3H 2 O

4HNO 3 (c) + Сu → Сu (NO 3) 2 + 2NO 2 + 2H 2 O

3. Interaction of metals with water

1) Active (alkali and alkaline earth metals) form a soluble base (alkali) and hydrogen:

2Na + 2H 2 O → 2NaOH + H 2

Ca+ 2H 2 O → Ca(OH) 2 + H 2

2) Metals of medium activity are oxidized by water when heated to oxide:

Zn + H 2 O – t° → ZnO + H 2

3) Inactive (Au, Ag, Pt) - do not react.

4. Displacement by more active metals of less active metals from solutions of their salts:

Cu + HgCl 2 → Hg + CuCl 2

Fe+ CuSO 4 → Cu+ FeSO 4

In industry, not pure metals are often used, but their mixtures - alloys in which the beneficial properties of one metal are complemented by the beneficial properties of another. So, copper has a low hardness and is of little use for the manufacture of machine parts, while alloys of copper with zinc ( brass) are already quite hard and are widely used in mechanical engineering. Aluminum has high ductility and sufficient lightness (low density), but is too soft. On its basis, an alloy with magnesium, copper and manganese is prepared - duralumin (duralumin), which, without losing useful properties aluminum, acquires high hardness and becomes suitable in the aircraft industry. Alloys of iron with carbon (and additives of other metals) are widely known cast iron And steel.

Metals in free form are reducing agents. However, the reactivity of some metals is low due to the fact that they are covered with surface oxide film, in varying degrees resistant to the action of such chemical reagents as water, solutions of acids and alkalis.

For example, lead is always covered with an oxide film; its transition into solution requires not only exposure to a reagent (for example, dilute nitric acid), but also heating. The oxide film on aluminum prevents its reaction with water, but is destroyed under the action of acids and alkalis. Loose oxide film (rust), formed on the surface of iron in moist air, does not interfere with the further oxidation of iron.

Under the influence concentrated acids are formed on metals sustainable oxide film. This phenomenon is called passivation. So, in concentrated sulfuric acid passivated (and then do not react with acid) such metals as Be, Bi, Co, Fe, Mg and Nb, and in concentrated nitric acid - metals A1, Be, Bi, Co, Cr, Fe, Nb, Ni, Pb , Th and U.

When interacting with oxidizing agents in acidic solutions, most metals turn into cations, the charge of which is determined by the stable oxidation state of a given element in compounds (Na +, Ca 2+, A1 3+, Fe 2+ and Fe 3+)

The reducing activity of metals in an acidic solution is transmitted by a series of stresses. Most metals are converted into a solution with hydrochloric and dilute sulfuric acids, but Cu, Ag and Hg - only with sulfuric (concentrated) and nitric acids, and Pt and Au - with "aqua regia".

Corrosion of metals

An undesirable chemical property of metals is their corrosion, i.e. active destruction (oxidation) upon contact with water and under the influence of oxygen dissolved in it (oxygen corrosion). For example, the corrosion of iron products in water is widely known, as a result of which rust is formed, and the products crumble into powder.

Corrosion of metals proceeds in water also due to the presence of dissolved CO 2 and SO 2 gases; an acidic environment is created, and H + cations are displaced by active metals in the form of hydrogen H 2 ( hydrogen corrosion).

The point of contact between two dissimilar metals can be especially corrosive ( contact corrosion). Between one metal, such as Fe, and another metal, such as Sn or Cu, placed in water, a galvanic couple occurs. The flow of electrons goes from the more active metal, which is to the left in the series of voltages (Re), to the less active metal (Sn, Cu), and the more active metal is destroyed (corrodes).

It is because of this that the tinned surface rusts. cans(tin-plated iron) when stored in a humid atmosphere and handled carelessly (iron quickly breaks down after even a small scratch is introduced, allowing iron to come into contact with moisture). On the contrary, the galvanized surface of an iron bucket does not rust for a long time, because even if there are scratches, it is not iron that corrodes, but zinc (a more active metal than iron).

Corrosion resistance for a given metal is enhanced when it is coated with a more active metal or when they are fused; for example, coating iron with chromium or making an alloy of iron with chromium eliminates the corrosion of iron. Chrome-plated iron and steel containing chromium ( stainless steel) have high corrosion resistance.

There are technological, physical, mechanical and chemical properties of metals. The physical ones include color, electrical conductivity. The characteristics of this group also include thermal conductivity, fusibility and density of the metal.

TO mechanical characteristics include plasticity, elasticity, hardness, strength, viscosity.

Chemical properties metals include corrosion resistance, solubility and oxidizability.

Characteristics such as "fluidity", hardenability, weldability, ductility, are technological.

Physical Properties

1. Color. Metals do not transmit light through themselves, that is, they are opaque. In reflected light, each element has its own hue - a color. Among technical metals, only copper and alloys with it have color. The remaining elements are characterized by a shade from silver-white to gray-steel.
2. Fusibility. This characteristic indicates the ability of the element under the influence of temperature to pass into a liquid state from a solid. Fusibility is considered the most important property metals. In the process of heating, all metals from a solid state pass into a liquid state. When the molten substance is cooled, a reverse transition occurs - from a liquid to a solid state.
3. Electrical conductivity. This characteristic indicates the ability to transfer electricity by free electrons. The electrical conductivity of metallic bodies is thousands of times greater than that of non-metallic ones. As the temperature increases, the conductivity of electricity decreases, and as the temperature decreases, accordingly, it increases. It should be noted that the electrical conductivity of alloys will always be lower than that of any metal that makes up the alloy.
4. Magnetic properties. The clearly magnetic (ferromagnetic) elements include only cobalt, nickel, iron, as well as a number of their alloys. However, in the process of heating to a certain temperature, these substances lose their magnetism. Individual iron alloys at room temperature are not ferromagnetic.
5. Thermal conductivity. This characteristic indicates the ability to transfer heat to a less heated one from a more heated body without visible movement of its constituent particles. The high level of thermal conductivity allows even and fast heating and cooling of metals. Among the technical elements, copper has the highest indicator.

Metals occupy a separate place in chemistry. The presence of appropriate characteristics allows the use of a particular substance in a certain area.

Chemical properties of metals

1. Corrosion resistance. Corrosion is the destruction of a substance as a result of an electrochemical or chemical relationship with environment. The most common example is the rusting of iron. Corrosion resistance is one of the most important natural characteristics of a number of metals. In this regard, substances such as silver, gold, platinum are called noble. Has high corrosion resistance Nickel and other non-ferrous metals are subject to destruction faster and more strongly than non-ferrous metals.
2. Oxidability. This characteristic indicates the ability of the element to react with O2 under the influence of oxidizing agents.
3. Solubility. Metals that have unlimited solubility in the liquid state can form solid solutions when solidified. In these solutions, atoms from one component are embedded in another component only within certain limits.

It should be noted that the physical and chemical properties of metals are one of the main characteristics of these elements.

The first material that people learned to use for their needs is stone. However, later, when a person became aware of the properties of metals, the stone moved far back. It is these substances and their alloys that have become the most important and main material in the hands of people. Household items, tools of labor were made from them, premises were built. Therefore, in this article we will consider what metals are, general characteristics, the properties and application of which are so relevant to this day. After all, literally immediately after the Stone Age followed whole galaxy metal: copper, bronze and iron.

Metals: general characteristics

What unites all representatives of these simple substances? Of course, this is the structure of their crystal lattice, types of chemical bonds and features of the electronic structure of the atom. After all, hence the characteristic physical properties that underlie the use of these materials by humans.

First of all, consider metals as chemical elements periodic system. In it, they are located quite freely, occupying 95 cells out of 115 known today. There are several features of their location in the general system:

• They form the main subgroups of groups I and II, as well as III, starting with aluminum.
• All side subgroups consist only of metals.
• They are located below the conditional diagonal from boron to astatine.

Based on such data, it is easy to see that non-metals are collected in the upper right part of the system, and the rest of the space belongs to the elements we are considering.

All of them have several features of the electronic structure of the atom:

The general characteristics of metals and non-metals makes it possible to identify patterns in their structure. So, crystal cell the first - metal, special. Its nodes contain several types of particles at once:

• ions;
• atoms;
• electrons.

A common cloud accumulates inside, called electron gas, which explains all the physical properties of these substances. Type chemical bond in metals of the same name with them.

Physical Properties

There are a number of parameters that unite all metals. Their general characteristics according to physical properties looks like that.

The listed parameters are the general characteristics of metals, that is, everything that unites them into one large family. However, it should be understood that there are exceptions to every rule. Moreover, there are too many elements of this kind. Therefore, within the family itself there are also divisions into various groups, which we will consider below and for which we will indicate the characteristic features.

Chemical properties

From the point of view of the science of chemistry, all metals are reducing agents. And, very strong. The fewer electrons in the outer level and the larger the atomic radius, the stronger the metal according to the specified parameter.

As a result, metals are able to react with:

This is just a general overview of chemical properties. After all, for each group of elements they are purely individual.

alkaline earth metals

The general characteristics of alkaline earth metals are as follows:

Thus, alkaline earth metals are common elements of the s-family, exhibiting high chemical activity and are strong reducing agents and important participants in biological processes in the body.

alkali metals

The general characteristic begins with their name. They received it for the ability to dissolve in water, forming alkalis - caustic hydroxides. Reactions with water are very violent, sometimes flammable. These substances are not found in free form in nature, since their chemical activity is too high. They react with air, water vapor, non-metals, acids, oxides and salts, that is, with almost everything.

This is explained by their electronic structure. At the outer level, there is only one electron, which they easily give away. These are the strongest reducing agents, which is why it took quite a long time to obtain them in their pure form. This was first done by Humphrey Davy already in the 18th century by electrolysis of sodium hydroxide. Now all representatives of this group are mined using this method.

The general characteristic of alkali metals is also that they constitute the first group of the main subgroup of the periodic system. All of them are important elements that form many valuable natural compounds used by man.

General characteristics of metals of d- and f-families

This group of elements includes all those whose oxidation state can vary. This means that, depending on the conditions, the metal can act as both an oxidizing agent and a reducing agent. Such elements have a great ability to enter into reactions. Among them a large number of amphoteric substances.

The common name for all these atoms is transition elements. They received it for the fact that, in terms of their properties, they really stand, as it were, in the middle, between typical metals s-family and non-metals of the p-family.

The general characteristic of transition metals implies the designation of their similar properties. They are the following:

• a large number of electrons in the outer level;
• large atomic radius;
• several degrees of oxidation (from +3 to +7);
• are on the d- or f-sublevel;
• form 4-6 large periods of the system.

How simple substances metals of this group are very strong, ductile and malleable, therefore they are of great industrial importance.

Side subgroups of the periodic system

The general characteristics of the metals of the secondary subgroups completely coincide with those of the transitional ones. And this is not surprising, because, in fact, it is exactly the same thing. It’s just that the side subgroups of the system are formed precisely by representatives of the d- and f-families, that is, transition metals. Therefore, we can say that these concepts are synonyms.

The most active and important of them are the first row of 10 representatives from scandium to zinc. All of them are of great industrial importance and are often used by man, especially for smelting.

Alloys

The general characteristics of metals and alloys makes it possible to understand where and how it is possible to use these substances. Such compounds have undergone great transformations in the last decades, because more and more new additives are being discovered and synthesized to improve their quality.

The most famous alloys today are:

• brass;
• duralumin;
• cast iron;
• steel;
• bronze;
• will win;
• nichrome and others.

What is an alloy? This is a mixture of metals obtained by smelting the latter in special furnace devices. This is done in order to obtain a product that is superior in properties pure substances, which form it.

Comparison of properties of metals and non-metals

If we talk about general properties, then the characteristics of metals and non-metals will differ in one very significant point: for the latter, similar features cannot be distinguished, since they differ greatly in their manifested properties, both physical and chemical.

Therefore, it is impossible to create such a characteristic for non-metals. It is only possible to separately consider the representatives of each group and describe their properties.

Chemical properties of metals: interaction with oxygen, halogens, sulfur and relation to water, acids, salts.

The chemical properties of metals are due to the ability of their atoms to easily donate electrons from the external energy level to become positively charged ions. Thus, in chemical reactions, metals act as energetic reducing agents. This is their main common chemical property.

The ability to donate electrons in atoms of individual metallic elements is different. The more easily a metal gives up its electrons, the more active it is, and the more vigorously it reacts with other substances. Based on the research, all metals were arranged in a row according to their decreasing activity. This series was first proposed by the outstanding scientist N. N. Beketov. Such a series of activity of metals is also called the displacement series of metals or the electrochemical series of metal voltages. It looks like this:

Li, K, Ba, Ca, Na, Mg, Al, Zn, Fe, Ni, Sn, Pb, H2, Cu, Hg, Ag, Рt, Au

Using this series, you can find out which metal is the active of the other. This series contains hydrogen, which is not a metal. Its visible properties are taken for comparison as a kind of zero.

Having the properties of reducing agents, metals react with various oxidizing agents, primarily with non-metals. Metals react with oxygen under normal conditions or when heated to form oxides, for example:

2Mg0 + O02 = 2Mg+2O-2

In this reaction, magnesium atoms are oxidized and oxygen atoms are reduced. The noble metals at the end of the row react with oxygen. Reactions with halogens actively occur, for example, the combustion of copper in chlorine:

Cu0 + Cl02 = Cu+2Cl-2

Reactions with sulfur most often occur when heated, for example:

Fe0 + S0 = Fe+2S-2

Active metals in the activity series of metals in Mg react with water to form alkalis and hydrogen:

2Na0 + 2H+2O → 2Na+OH + H02

Metals of medium activity from Al to H2 react with water under more severe conditions and form oxides and hydrogen:

Pb0 + H+2O Chemical properties of metals: interaction with oxygen Pb+2O + H02.

The ability of a metal to react with acids and salts in solution also depends on its position in the displacement series of metals. Metals to the left of hydrogen in the displacement series of metals usually displace (reduce) hydrogen from dilute acids, and metals to the right of hydrogen do not displace it. So, zinc and magnesium react with acid solutions, releasing hydrogen and forming salts, while copper does not react.

Mg0 + 2H+Cl → Mg+2Cl2 + H02

Zn0 + H+2SO4 → Zn+2SO4 + H02.

Metal atoms in these reactions are reducing agents, and hydrogen ions are oxidizing agents.

Metals react with salts in aqueous solutions. Active metals displace less active metals from the composition of salts. This can be determined from the activity series of metals. The reaction products are a new salt and a new metal. So, if an iron plate is immersed in a solution of copper (II) sulfate, after a while copper will stand out on it in the form of a red coating:

Fe0 + Cu+2SO4 → Fe+2SO4 + Cu0 .

But if a silver plate is immersed in a solution of copper (II) sulfate, then no reaction will occur:

Ag + CuSO4 ≠ .

To carry out such reactions, one should not take too active metals (from lithium to sodium), which are capable of reacting with water.

Therefore, metals are able to react with non-metals, water, acids and salts. In all these cases, the metals are oxidized and are reducing agents. To predict the flow chemical reactions with the participation of metals, a displacement series of metals should be used.

INTERACTION OF METALS WITH NONMETALS

Non-metals exhibit oxidizing properties in reactions with metals, accepting electrons from them and recovering.

Interaction with halogens

Halogens (F 2, Cl 2, Br 2, I 2 ) are strong oxidizing agents, therefore, all metals interact with them under normal conditions:

2Me+ n Hal 2 → 2 MeHal n

The product of this reaction is a metal halide salt ( MeF n -fluoride, MeCl n -chloride, MeBr n -bromide, MeI n -iodide). When interacting with a metal, the halogen is reduced to the lowest oxidation state (-1), andnequal to the oxidation state of the metal.

The reaction rate depends on the chemical activity of the metal and halogen. The oxidative activity of halogens decreases in the group from top to bottom (from F to I ).

Interaction with oxygen

Oxygen oxidizes almost all metals (except Ag, Au, Pt ), resulting in the formation of oxides Me 2 O n .

active metals easily interact with atmospheric oxygen under normal conditions.

2 Mg + O 2 → 2 MgO (with flash)

Intermediate activity metals also react with oxygen at ordinary temperature. But the rate of such a reaction is significantly lower than with the participation of active metals.

Inactive metals oxidized by oxygen when heated (combustion in oxygen).

oxides Chemical properties of metals can be divided into three groups:

1. Basic oxides ( Na 2 O, CaO, Fe II O, Mn II O, Cu I O etc.) are formed by metals in low oxidation states (+1, +2, as a rule, below +4). Basic oxides interact with acidic oxides and acids to form salts:

CaO + CO 2 → CaCO 3

CuO + H 2 SO 4 → CuSO 4 + H 2 O

2. Acid oxides ( Cr VI O 3 , Fe VI O 3 , Mn VI O 3 , Mn 2 VII O 7 etc.) are formed by metals in high oxidation states (as a rule, above +4). Acid oxides interact with basic oxides and bases to form salts:

FeO 3 + K 2 O → K 2 FeO 4

CrO 3 + 2KOH → K 2 CrO 4 + H 2 O

3. Amphoteric oxides ( BeO, Al 2 O 3, ZnO, SnO, MnO 2, Cr 2 O 3, PbO, PbO 2 etc.) have a dual nature and can interact with both acids and bases:

Cr 2 O 3 + 3H 2 SO 4 → Cr 2 (SO 4) + 3H 2 O

Cr 2 O 3 + 6NaOH → 2Na 3

Interaction with sulfur

All metals interact with sulfur (except Au ), forming salts - sulfides Me 2 S n . In this case, sulfur is reduced to the oxidation state of "-2". Platinum ( Pt ) interacts with sulfur only in a finely divided state. alkali metals, and Ca and Mg react with sulfur when heated with an explosion. Zn, Al (powder) and Mg in reaction with sulfur give a flash. In the direction from left to right in the activity series, the rate of interaction of metals with sulfur decreases.

Interaction with hydrogen

With hydrogen, some active metals form compounds - hydrides:

2 Na + H 2 → 2 NaH

In these compounds, hydrogen is in its rare oxidation state "-1".

E.A. Nudnova, M.V. Andriukhova