Chemical metals. Chemical properties of metals with examples

The structure of metals atoms determines not only characteristic physical properties. simple substances - Metals, but also common chemical properties.

With a large variety, all chemical reactions of metals refer to redox and can only be two types: compounds and substitutions. Metals are capable of chemical reactions to give electrons, that is, to be reducing agents, manifest only a positive degree of oxidation in the resulting compounds.

IN general This can be expressed by the scheme:
ME 0 - NE → ME + N,
where Metal is a simple substance, and a 0 + n is a metal chemical element in the compound.

Metals are able to give their valence electrons atoms of non-metals, hydrogen ions, ions of other metals, and therefore will react with non-metals - simple substances, water, acids, salts. However, the restorative capacity of metals is different. The composition of the reaction of metals with different substances depends on the oxidative ability of substances and conditions under which the reaction proceeds.

At high temperatures, most metals burn in oxygen:

2mg + O 2 \u003d 2mgo

Not oxidized in these conditions only gold, silver, platinum and some other metals.

With halogens, many metals react without heating. For example, aluminum powder when mixing with bromine lights up:

2AL + 3Br 2 \u003d 2Albr 3

In some cases, hydroxides are formed in some cases. Very active under normal conditions interact with water alkali metals, as well as calcium, strontium, barium. The scheme of this reaction in general looks like this:

Me + HOH → ME (OH) N + H 2

Other metals react with water when heated: magnesium when it is boiling, iron in water pairs during red boiling. In these cases, metal oxides are obtained.

If the metal reacts with acid, then it is part of the salt generated. When the metal interacts with the acid solutions, it can oxidize hydrogen ions available in this solution. Abbreviated ion equation In general, you can record like this:

ME + NH + → ME N + + H 2

Stronger oxidative propertiesThan hydrogen ions have anions of such oxygen-containing acids, such as concentrated sulfur and nitrogen. Therefore, those metals are reacting with these acids that are not capable of oxidizing hydrogen ions, for example, copper and silver.

In the interaction of metals with salts, substitution reaction occurs: electrons from the replacement atoms - more active metal go to the ions of the substituted - less active metal. That network occurs a metal substitution with metal in salts. These reactions are not reversible: if the metal and displaces the metal into salts, then the metal in will not exhibit the metal and from the salts solution.

In the order of decrease in the chemical activity, manifested in the reactions of displacement of metals of each other from aqueous solutions Their salts, metals are located in an electrochemical row of stresses (activity) of metals:

Li → Rb → K → Ba → SR → Ca → Na → Mg → Al → Mn → Zn → CR → → Fe → Zn → CR → → Fe → CD → CO → → Fe → CD → CO → Ni → SN → PB → Cu → SB → Bi → Cu → Hg → AG → PD → PT → AU

Metals located in this series of left are more active and able to outpipe the following metals from solutions of salts.

Hydrogen is included in the electrochemical row of metal voltages, as the only non-metall, separating with metals, to form positively charged ions. Therefore, hydrogen replaces some metals in their salts and itself can be replaced by many metals in acids, for example:

Zn + 2 HCl \u003d ZnCl 2 + H 2 + Q

Metals facing an electrochemical row of voltages to hydrogen are displaced from solutions of many acids (salt, sulfur, etc.), and all the following, for example, copper do not displace.

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Metals are active reducing agents with a positive degree of oxidation. Thanks to the chemical properties, the metals are widely used in industry, metallurgy, medicine, construction.

Metal activity

In reactions, the atoms of metals give valence electrons and are oxidized. The more energy levels and less electrons have an atom of a metal, the easier it is to give electrons and enter the reaction. Therefore, metal properties increase from top to bottom and right to left in the Mendeleev table.

Fig. 1. Changing metal properties in the Mendeleev table.

The activity of simple substances is shown in the electrochemical row of stresses of metals. The left of hydrogen is active metals (activity increases to the left edge), on the right - inactive.

Alkaline metals, in the first group of periodic table and the left of the hydrogen, in the electrochemical row of voltages are exhibiting the greatest activity. They react with many substances at room temperature. They are alkaline earth metals included in the group II. They react with most substances when heated. Metals in electrochemical row from aluminum to hydrogen (medium activity) require additional conditions for reaction entry.

Fig. 2. Electrochemical row of metal voltages.

Some metals exhibit amphoteric properties or duality. Metals, their oxides and hydroxides react with acids and bases. Most metals react only with some acids, replacing hydrogen and forming salt. The most pronounced dual properties show:

• aluminum;
• lead;
• zinc;
• iron;
• copper;
• beryllium;
• chromium.

Each metal is able to exhibit the other metal from the salts standing in the electrochemical row. Metals on the left of hydrogen are displaced from dilute acids.

Properties

Features of the interaction of metals with different substances Presented in the table of chemical properties of metals.

Reaction	Features	The equation
With oxygen	Most metals form oxide films. Alkaline metals are self-proposal in the presence of oxygen. At the same time, the sodium forms peroxide (Na 2 O 2), the remaining metals of the group I - Opperoxides (RO 2). When heated, alkaline earth metals are self-proposal, metals of medium activity - oxidized. In the interaction with oxygen, gold and platinum do not enter	4Li + O 2 → 2Li 2 O; 2NA + O 2 → Na 2 O 2; K + O 2 → KO 2; 4Al + 3O 2 → 2AL 2 O 3; 2CU + O 2 → 2CUO
With hydrogen	At room temperature, alkaline reacts, when heated - alkaline earth. Beryllium does not react. Magnesia additionally need high pressure	SR + H 2 → SRH 2; 2NA + H 2 → 2NAH; Mg + H 2 → MGH 2
	Only active metals. Lithium reacts at room temperature. The remaining metals - when heated	6Li + N 2 → 2LI 3 N; 3CA + N 2 → Ca 3 N 2
With carbon	Lithium and sodium, the rest - when heated	4Al + 3c → Al 3 C4; 2li + 2c → Li 2 C 2
	Gold and platinum do not interact	2k + s → k 2 s; Fe + S → Fes; Zn + S → ZNS
With phosphorus	When heated	3CA + 2P → CA 3 P 2
With halogen	Only lowactive metals are not reacting, copper - when heated	CU + CL 2 → CUCL 2
	Alkaline and some alkaline earth metals. When heated, medium activity metals react under conditions of sour or alkaline medium	2NA + 2H 2 O → 2NAOH + H 2; CA + 2H 2 O → Ca (OH) 2 + H 2; PB + H 2 O → PBO + H 2
With acids	Metals to the left of hydrogen. Copper dissolves B. concentrated acidsoh	Zn + 2HCl → ZnCl 2 + 2H 2; Fe + H 2 SO 4 → FESO 4 + H 2; Cu + 2H 2 SO 4 → CUSO 4 + SO 2 + 2H 2 O
With alkalis	Only amphoteric metals	2Al + 2KOH + 6H 2 O → 2k + 3h 2
	Active replace less active metals	3NA + AlCl 3 → 3NACL + Al

Metals interact with each other and form intermetallic compounds - 3CU + AU → CU 3 AU, 2NA + SB → Na 2 SB.

Application

The total chemical properties of metals are used to create alloys, detergents, are used in catalytic reactions. Metals are present in batteries, electronics, in bearing structures.

The main industries are specified in the table.

Fig. 3. Bismuth.

What did we know?

From the lesson of grade 9, chemistry learned about the basic chemical properties of metals. The ability to interact with simple and complex substances determines the activity of metals. The more active the metal, the easier it enters the reaction under normal conditions. Active metals react with halogens, non-metals, water, acids, salts. Amphoteric metals interact with alkalis. Non-effective metals do not react with water, halogens, most non-metals. Briefly reviewed the branch of the application. Metals are used in medicine, industry, metallurgy, electronics.

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If in the periodic table of elements D.I. IETELEEVE to hold a diagonal from beryllium to Astatu, then elements-metals will be left at the bottom of the diagonal (elements of side subgroups include, highlighted in blue), and on the right - non-metal elements (highlighted yellow). Elements located near the diagonal - semi-metals or metalloids (B, Si, Ge, SB, etc.), have a dual character (highlighted with pink color).

As can be seen from the figure, the overwhelming majority of elements are metals.

According to chemical nature Metals are chemical elements whose atoms give electrons from an external or antisomine energy level, forming positively charged ions.

Almost all metals have relatively large radii and a small number of electrons (from 1 to 3) at the external energy level. Metals are characterized by low electronegability values \u200b\u200band rehabilitation properties.

The most typical metals are located at the beginning of periods (starting from the second), further left to the right of the metal properties weaken. In the group from top to bottom, metal properties are enhanced, because the radius of atoms increases (due to an increase in the number of energy levels). This leads to a decrease in electronegability (the ability to attract electrons) of elements and reducing rehabilitation properties (the ability to give electrons to other atoms in chemical reactions).

Typical Metals are S-elements (elements of the Ia-group from Li to FR. elements of the pa-group from Mg to RA). General electronic formula of their NS 1-2 atoms. They are characterized by the degrees of oxidation + i and + ii, respectively.

A small number of electrons (1-2) at the external energy level of typical metals atoms implies a light loss of these electrons and the manifestation of strong reducing properties, which reflect low electronegability values. Hence the limitedness of the chemical properties and methods for obtaining typical metals.

A characteristic feature of typical metals is the desire of their atoms to form cations and ion chemical bonds with non-metal atoms. Connections of typical metals with non-metals are ionic crystals "Metallanion Nemetalla cation", for example K + Vg -, Ca 2+ per 2-. The cations of typical metals also consists of compounds with complex anions - hydroxides and salts, for example, Mg 2+ (ON -) 2, (Li +) 2СO 3 2-.

Metals of A-groups, forming amphoterity diagonal in the periodic system ve-al-GE-SB-RO, as well as metal adjacent to them (GA, IN, TL, SN, RB, BI) do not show typical metal properties. General electronic formula of their atoms nS. 2 nP. 0-4 involves a greater diversity of oxidation degrees, the greater ability to hold its own electrons, gradually lowering their restorative ability and the appearance of oxidative ability, especially in high degrees oxidation (characteristic examples - compounds of TL III, Pb IV, VI V). Such chemical behavior is characteristic and for most (D-elements, i.e. elements of B-groups Periodic system (typical examples - amphoteric elements of CR and Zn).

This is a manifestation of duality (amphoterity) properties, at the same time metal (basic) and non-metallic, due to the nature chemical bond. In the solid state, the connection of nonypical metals with non-metals contains predominantly covalent bonds (but less durable than the links between non-metals). In solution, these bonds are easily broken, and the compounds are dissociated on ions (fully or partially). For example, metal gallium consists of Ga 2 molecules, in a solid state of aluminum and mercury chlorides (II), Alsl 3 and NgSl 2 contain strongly covalent bonds, but in a solution of ALSL 3 dissociates almost completely, and the NGSL 2 is in a very small degree (and then on the ions NgSl + and Sl -).

General physical properties of metals

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

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

2) Metal shine and opacity. This is due to the interaction of free electrons with inclusive light.

3) Electrical conductivity. It is explained by the directional movement of free electrons from the negative pole to the positive influence of a small potential difference. When heated, the electrical conductivity decreases, because With increasing temperature, fluctuations of atoms and ions in the nodes of the crystal lattice are enhanced, which makes it difficult to the directional motion of the "electronic gas".

4) Thermal conductivity. It is due to the high mobility of free electrons, due to which the temperature is rapidly aligning the mass of metal. The greatest thermal conductivity is bismuth and mercury.

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

6) Density. It is the less less than the atomic mass of the metal and more radius of the atom. The easiest lithium (ρ \u003d 0.53 g / cm3); Heavy - osmium (ρ \u003d 22.6 g / cm3). Metals having a density of less than 5 g / cm3 are considered "light metal".

7) Melting and boiling temperatures. The most elbow metal - mercury (mp \u003d -39 ° C), the most refractory metal - tungsten (T ° field \u003d 3390 ° C). Metals with T ° PL. Above 1000 ° C are considered refractory, lower - low-melting.

General chemical properties of metals

Strong reducing agents: ME 0 - Nē → Me n +

A number of stresses characterize the comparative activity of metals in oxidative reducing reactions in aqueous solutions.

I. Metal reactions with non-metals

1) with oxygen:
2mg + O 2 → 2mgo

2) with gray:
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 alkaline and alkaline earth metals react):
2li + H 2 → 2lih

CA + H 2 → CAH 2

II. Acid metals reactions

1) Metals standing in an electrochemical row of stresses up to H restore non-oxidant 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 sulfur with metals hydrogen never stands out!

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 (K) + 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 (K) + Cu → Cu (NO 3) 2 + 2NO 2 + 2H 2 O

III. Metal interaction with water

1) active (alkaline 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 with water when heated to oxide:

Zn + H 2 O - T ° → Zno + H 2

3) Inactive (AU, AG, PT) - do not react.

IV. The outstanding of less active metals from solutions of their salts:

CU + HGCL 2 → HG + CUCL 2

Fe + Cuso 4 → Cu + Feso 4

In industry are often used not pure metals, but mixtures - alloysin which the beneficial properties of one metal are complemented by the beneficial properties of the other. So, copper has low hardness and is unsuitable for the manufacture of machine parts, copper alloys with zinc ( brass) are already solid and widely used in mechanical engineering. Aluminum has high plasticity and sufficient ease (low density), but too soft. Based on it is prepared alloy with magnesium, copper and manganese - Duralumin (Dural), which, without losing useful properties Aluminum, acquires high hardness and becomes suitable in aircraft. Iron alloys with carbon (and additives of other metals) - these are well-known cast ironand steel.

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

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

Under the influence concentrated acids on metals formed sustainable Oxyde film. This phenomenon is called passivation. So, in concentrated sulfuric acid Passivable (and after that they do not react with acid) Such metals, as ve, Bi, CO, FE, MG and NB, and in concentrated nitric acid - Metals A1, ve, Bi, CO, SG, FE, NB, Ni, Rye , TH and U.

When interacting with oxidizing agents in acid solutions, most metals go into cations, the charge of which is determined by a stable degree of oxidation of this element in compounds (NA +, Ca 2+, A1 3+, Fe 2+ and Fe 3+)

The reductive activity of metals in an acid solution is transmitted by a number of voltages. Most metals are translated into a solution of hydrochloric and diluted with sulfuric acids, but Cu, Ag and Hg - only sulfur (concentrated) and nitric acids, and pt and ai - "tsarist vodka".

Corrosion Metals

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

Metal corrosion proceeds in water also due to the presence of dissolved gases from 2 and SO 2; The acid medium is created, and the H + cations are displaced by active metals in the form of hydrogen H 2 ( hydrogen corrosion).

The contact of two heterogeneous metals is particularly corrosion-dangerous ( contact corrosion). Between one metal, for example Fe, and other metal, for example, SN or Cu, placed in water, an electroplated pair occurs. The electron flow comes from a more active metal that is standing in the left in a row of stresses (re), to a less active metal (SN, CU), and more active metal is destroyed (corrodes).

It is because of this that rust is a tinned surface of tin cans (tin coated) during storage in a wet atmosphere and a careless handling of them (iron is quickly destroyed after the appearance of at least a small scratch that admits the contact of iron with moisture). On the contrary, the galvanized surface of the iron bucket does not rust for a long time, because even if there is scratches, it is corroded by iron, but zinc (more active metal than iron).

Corrosion resistance for this metal is enhanced with its coating with a more active metal or when they are fusing them; So, the coating of iron chromium or the manufacture of iron alloy with chromium eliminates iron corrosion. Chrome-plated iron and steel containing chrome ( stainless steel), have high corrosion resistance.

electrometallurgy, i.e., the production of metals by electrolysis of melts (for the most active metals) or salts solutions;

pyrometallurgy, i.e. restoration of metals from ores at high temperatures (for example, obtaining iron in the domain process);

hydrometallurgy, i.e. the release of metals from the solutions of their salts with more active metals (for example, the preparation of copper from the suction solution 4 with the action of zinc, iron or aluminum).

In nature, sometimes native metals (characteristic examples - Ag, AU, PT, NG), but more often, the metals are in the form of connections ( metal ores). In the prevalence of B. earth Kore Metals are different: from the most common - AL, NA, CA, FE, MG, K, TI) to the rarest - VI, IN, AG, AU, PT, RE.

According to its chemical activity, the metals vary greatly. About the chemical activity of the metal can be roughly judged by its position in.

The most active metals are located at the beginning of this series (left), the most lowactive - at the end (right).
Reactions with simple substances. Metals come in reaction with non-metals to form binary compounds. The conditions for the restoration of reactions, and sometimes their products differ greatly for different metals.
For example, alkali metals are actively reacting with oxygen (including in the air composition) at room temperature with the formation of oxides and peroxides

4Li + O 2 \u003d 2Li 2 O;
2NA + O 2 \u003d Na 2 O 2

Metals of medium activity react with oxygen when heated. At the same time, oxides are formed:

2mg + O 2 \u003d T 2MGO.

Non-effective metals (for example, gold, platinum) are not reacting with oxygen and therefore in air practically do not change their gloss.
Most metals when heated with sulfur powder form appropriate sulphides:

Reactions with complex substances. Metals react to compounds of all classes - oxides (including water), acid, bases and salts.
Active metals are rapidly interacting with water at room temperature:

2Li + 2H 2 O \u003d 2LIOH + H 2;
Ba + 2H 2 O \u003d Ba (OH) 2 + H 2.

The surface of such metals, such as magnesium and aluminum, is protected by a dense film of the corresponding oxide. This prevents the flow of reaction with water. However, if this film removes or disrupt its integrity, then these metals also actively react. For example, powdered magnesium reacts with hot water:

Mg + 2H 2 O \u003d 100 ° C Mg (OH) 2 + H 2.

At elevated water temperature, the reaction is reacted and less active metals: Zn, Fe, Mil, and others. At the same time, appropriate oxides are formed. For example, when the water vapor passes over hot iron chips, the reaction proceeds:

3Fe + 4H 2 O \u003d T FE 3 O 4 + 4H 2.

Metals facing a row of activity to hydrogen react with acids (except HNO 3) to form salts and hydrogen. Active metals (K, Na, Ca, Mg) react with acid solutions very violently (at high speed):

Ca + 2HCl \u003d CaCl 2 + H 2;
2Al + 3H 2 SO 4 \u003d Al 2 (SO 4) 3 + 3H 2.

Non-effective metals are often practically dissolved in acids. This is due to the formation of an insoluble salt on their surface. For example, lead, which stands in a series of activity to hydrogen, is practically not dissolved in dilute sulfur and hydrochloric acids Due to the formation on its surface of insoluble salts (PBSO 4 and PBCl 2).

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Under metals, they mean a group of elements that is presented in the form of the simplest substances. They possess characteristic properties, namely, high electrical and thermal conductivity, positive temperature coefficient of resistance, high plasticity and metal glitter.

Note that out of 118 chemical elementswho were open to this momentTo the metals should be attributed:

• among the group of pic-earth metals 6 elements;
• among alkali metals 6 elements;
• among transition metals 38;
• in the group of light metals 11;
• among semi-metals of 7 elements,
• 14 among Lantanoids and Lantan,
• 14 in the Aktinoid and Actinium group,
• Beyond the definition there are beryllium and magnesium.

Based on this, 96 elements include metals. Consider more detailed with the reacting metals. Since at the external electron level in most metals there is a small amount of electrons from 1 to 3, then in most of their reactions can act as reducing agents (that is, they give their electrons to other elements).

Reactions with the easiest elements

• In addition to gold and platinum, absolutely all metals react with oxygen. We also note that the reaction at high temperatures occurs with silver, but silver oxide (II) at normal temperatures is not formed. Depending on the properties of the metal, oxides, pressure and peroxides are formed as a result of reaction with oxygen.

We give examples of each of the chemical education:

1. lithium oxide - 4Li + O 2 \u003d 2Li 2 O;
2. potassium propeller - K + O 2 \u003d KO 2;
3. sodium peroxide - 2NA + O 2 \u003d Na 2 O 2.

In order to obtain peroxide oxide, it must be restored by the same metal. For example, Na 2 O 2 + 2NA \u003d 2NA 2 O. with low-active and with average metals, such a reaction will occur only when heated, for example: 3Fe + 2O 2 \u003d Fe 3 O 4.

• With nitrogen, the metals can react only with active metals, but only lithium can interact at room temperature, while forming nitrides - 6Li + N 2 \u003d 2LI 3 N, but when heated is such chemical reaction 2AL + N 2 \u003d 2ALN, 3CA + N 2 \u003d Ca 3 N 2.
• With gray, as well as with oxygen, absolutely all metals react, while the exception is gold and platinum. Note that iron can only interact when heated with gray, at the same time, sulphide: Fe + S \u003d Fes
• Only active metals can react with hydrogen. These include metals of the IA Group and IIa, except Berilia. Such reactions can be carried out only when heated by forming hydrides.

  Since the degree of hydrogen oxidation is considered? 1, then the metals in this case act as reducing agents: 2NA + H 2 \u003d 2NAh.

• The most active metals are also reacting with carbon. As a result of this reaction, acetylenes or methanides are formed.

Consider which metals react with water and what do they give as a result of this reaction? Acetylene when interacting with water will produce acetylene, and methane will result from the reaction of water with metabins. We give examples of reaction data:

1. Acetylene - 2NA + 2C \u003d Na 2 C 2;
2. Methane - Na 2 C 2 + 2H 2 O \u003d 2NAOH + C 2 H 2.

Acid reactions with metals

Metals with acids can also react differently. With all the acids, only those metals react with the electrochemical activity of metals to hydrogen.

We give an example of a substitution reaction, which shows with which the metals react. In a different way, such a reaction is called redox: Mg + 2HCl \u003d MgCl 2 + H 2 ^.

Some acids can also interact with metals that stand after hydrogen: Cu + 2H 2 SO 4 \u003d Cuso 4 + SO 2 ^ + 2H 2 O.

Note that the dilute such acid can react with the metal according to the above classic scheme: Mg + H 2 SO 4 \u003d MgSO 4 + H 2 ^.