Characteristic chemical properties of simple substances - metals
Most chemical elements refer to metals - 92 of 114 well-known elements. Metals - These are chemical elements whose atoms give electrons of external (and some - and the antisomial) electronic layer, turning into positive ions. This property of atoms of metals is determined by that they have relatively large radii and small number of electrons (Basically from 1 to 3 on the outer layer). The exception is only 6 metals: Germany, tin atoms, lead on the outer layer have 4 electrons, antimony and bismuth atoms - 5, polonium atoms - 6. For metals atoms characterized small electronegability values(from 0.7 to 1.9) and exclusively restorative properties, i.e. the ability to give electrons. In the periodic system of chemical elements, D. I. Mendeleev metals are below diagonal Bor - Astat, as well as above it, in side subgroups. In the periods and main subgroups, the regularities in the change in metallic, and therefore the restoration properties of the atoms of the elements are valid.
Chemical elements located near Diagonal Bor - Astat (BE, AL, TI, GE, NB, SB, etc.), possess dual properties: In some of its compounds behave like metals, in others - the properties of non-metals are shown. In adverse subgroups, the restoration properties of metals with an increase in the sequence number are most often reduced.
Compare the activity of the metals known to you I group of a side subgroup: CU, AG, AU; The second group of the side subgroup: zn, cd, hg - and you will be sure of it yourself. This can be explained by the fact that the strength of the supply of valence electrons with the nucleus at the metals data atoms are more affected by the charge of the kernel, and not the radius of the atom. The magnitude of the charge of the kernel increases significantly, the attraction of electrons to the kernel is enhanced. The radius of the atom is also increasing, but not so much as the main subgroups.
Simple substances formed by chemical elements - metals, and complex metal-containing substances play a crucial role in the mineral and organic "life" of the Earth. It suffices to recall that atoms (ions) of metal elements are an integral part of the compounds that determine the metabolism in the human body, animals. For example, in the blood of a person found 76 elements, and only 14 are not metals.
In the human body, some elements of metals (calcium, potassium, sodium, magnesium) are present in large quantities, i.e. are macroelements. And such metals, like chrome, manganese, iron, cobalt, copper, zinc, molybdenum are present in small quantities, i.e. it is trace elements. If a person weighs 70 kg, then in its body is contained (in grams): calcium - 1700, potassium - 250, sodium - 70, magnesium - 42, iron - 5, zinc - 3. All metals are extremely important, health problems arise and With their lack, and in excess.
For example, sodium ions regulate the water content in the body, the transfer of nerve impulses. Its disadvantage leads to headaches, weakness, weak memory, loss of appetite, and excess - to an increase in blood pressure, hypertension, heart disease.
Simple substances - metals
With the development of production of metals (simple substances) and alloys, the emergence of civilization (Bronze Age, Iron Age) is associated. The scientific and technical revolution, which affected and the industry, and the social sphere, which began, and the production of metals, which began approximately 100 years ago. Based on tungsten, molybdenum, titanium and other metals began to create corrosion-resistant, superhard, refractory alloys whose application has greatly expanded mechanical engineering. In nuclear and cosmic technology, tungsten and rhenium alloys make parts operating at temperatures up to 3000 ° C; Medicine use surgical instruments from tantalum and platinum alloys, unique ceramics based on titanium and zirconium oxides.
And, of course, we should not forget that in most alloys a long-known metal iron is used, and the basis of many light alloys is comparatively "young" metals - aluminum and magnesium. Supernovae became composite materials representing, for example, a polymer or ceramics, which inside (as concrete with iron rods) are hardened with metal fibers from tungsten, molybdenum, steel and other metals, and alloys - it all depends on the goal required to achieve the properties of the material. The figure shows the scheme of the crystal lattice of metallic sodium. In it, every sodium atom is surrounded by eight neighbors. At the sodium atom, like all metals, there are many free valence orbitals and little valence electrons. Sodium atom electronic formula: 1S 2 2S 2 2P 6 3S 1 3P 0 3D 0, where 3S, 3P, 3D - Valental orbitals.
The only valence electron of the sodium atom 3s 1 It may occupy any of the nine-free orbitals - 3s (one), 3r (three) and 3D (five), because they are not very different in the level of energy. Under the rapprochement of atoms when the crystal lattice is formed, the valence orbitals of neighboring atoms are overlapped, due to which the electrons are freely moving from one orbital to another, communicating between all the atoms of the metal crystal. Such a chemical connection is called metallic.
Metal bond form elements whose atoms on the outer layer have little valence electrons compared with a large number of external energy orbitals. Their valence electrons are weakly held in the atom. Electrons communicating, are common and move along the entire crystal lattice in general neutral metal. Metal bond substances are inherent with metal crystal lattices, which are usually depicted schematically as shown in the figure. Cations and metals atoms located in the nodes of the crystal lattice provide its stability and strength (the common electrons are depicted in the form of black small balls).
Metal communication - This is a connection in metals and alloys between atom-ions of metals located in the nodes of the crystal lattice carried out by the communal valence electrons. Some metals crystallize in two or more crystalline forms. This property of substances is to exist in several crystalline modifications - called polymorphism. Polymorphism of simple substances is known as Allhotropia. For example, iron has four crystalline modifications, each of which is stable at a certain temperature range:
α - resistant to 768 ° C, ferromagnetic;
β - resistant from 768 to 910 ° C, non-ferromagnetic, i.e. paramagnetic;
γ is resistant from 910 to 1390 ° C, neferromagnetic, i.e. paramagnetic;
Δ - resistant from 1390 to 1539 ° C (£ ° PL iron), neferromagnetic.
Tin has two crystal modifications:
α - resistant below 13.2 ° C (p \u003d 5.75 g / cm 3). This is a gray tin. It has a crystalline diamond type lattice (atomic);
β is resistant above 13.2 ° C (p \u003d 6.55 g / cm 3). This is a white tin.
White Tin - Silver-White Very Soft Metal. When cooling below 13.2 ° C, it is crumpled into the gray powder, since its specific volume increases significantly. This phenomenon received the name of the "tin plague".
Of course, a special kind chemical bond and the type of metals crystal lattice must determine and explain their physical properties. What are they? This is a metal gloss, plasticity, high electrical conductivity and thermal conductivity, an increase in electrical resistance with increasing temperature, as well as significant properties such as density, high melting and boiling temperatures, hardness, magnetic properties. The mechanical effect on the crystal with a metal crystal lattice causes the displacement of the layers of ion-atoms relative to each other (Fig. 17), and since the electrons move across the entire crystal, the bond breaks does not occur, therefore large plasticity is characteristic of the metals. A similar effect on a solid with covalent bonds (atomic crystalline lattice) leads to a breaking of covalent bonds. The rupture of connections in the ion lattice leads to a mutual repulsion of the same name of charged ions. Therefore, substances with atomic and ion crystal lattices are fragile. The most plastic metals are AU, AG, SN, PB, ZN. They are easily pulled in a wire, sufficient forging, pressing, rolling into sheets. For example, from gold can be made of a gold foil with a thickness of 0.003 mm, and from 0.5 g of this metal can be pulled out a thread of 1 km long. Even mercury, which at room temperature is liquid, at low temperatures in solid state becomes a forging, like lead. Not possess plasticity only Bi and Mn, they are fragile.
Why are metals have a characteristic shine, and are also opaque?
Electrons that fill the intelligent space reflect light rays (and not let the glass), most of the metals in equal degree Scatter all the rays of the visible part of the spectrum. Therefore, they have silver-white or gray. Strontium, gold and copper are more absorbed by short waves (close to purple color) and reflect long waves of the light spectrum, so they have light yellow, yellow and "copper" colors. Although in practice, the metal does not always seem to us with a "light body". First, its surface can oxidize and lose shine. Therefore, native copper looks greenish. And secondly, and pure metal may not shine. Very subtle sheets of silver and gold have a completely unexpected look - they have bluish-green. And the small powders of metals seem dark gray, even black. Silver, aluminum, palladium have the greatest reflectivity. They are used in the manufacture of mirrors, including in spotlights.
Why are metals have high electrical conductivity and thermal conductors?
Chaotic moving electrons in the metal under the influence of the applied electrical voltage acquire directional motion, i.e. spend electricity. With increasing metal temperature, the amplitudes of oscillations in the nodes of the crystal lattice of atoms and ions increase. This makes it difficult to move the electrons, the electrical conductivity of the metal falls. At low temperatures, the oscillatory movement, on the contrary, is strongly reduced and the electrical conductivity of metals increases sharply. Near the absolute zero, metal resistance is practically absent, most metals appear superconductivity.
It should be noted that non-metals with electrical conductivity (for example, graphite), at low temperatures, on the contrary, do not conduct an electric current due to the lack of free electrons. And only with the increase in temperature and the destruction of some covalent bonds, their electrical conductivity begins to increase. The greatest electrical conductivity is silver, copper, as well as gold, aluminum, the smallest - manganese, lead, mercury.
Most often with the same pattern, as well as electrical conductivity, thermal conductivity of metals changes. It is due to the large mobility of the free electrons, which, facing the oscillating ions and atoms, exchange energy with them. There is a temperature alignment throughout the piece of metal.
Mechanical strength, density, melting point of metals are very different. Moreover, with an increase in the number of electrons connecting ion-atoms, and the decrease in the interatomic distance in the crystals, the indicators of these properties increase.
So, alkali metals (Li, K, NA, RB, CS), which have atoms one valence electron, soft (cut by a knife), with a small density (lithium - the lightest metal with p \u003d 0.53 g / cm 3) and melted at low temperatures (for example, the cesium melting point is 29 ° C). The only metal, liquid under normal conditions - mercury - has a melting point equal to -38,9 ° C. Calcium having two electrons at the external energy level of atoms is much more hard and melted at a higher temperature (842 ° C). An even stronger is a crystal lattice formed by scandium ions, which has three valence electron. But the most durable crystalline lattices, large density and melting points are observed in metals of side subgroups V, VI, VII, VIII groups. This is due to the fact that for metals of side subgroups having unpaired valence electrons on D-prying, it is characterized by the formation of very strong covalent bonds between atoms, in addition to the metal, electrically carried out by electrons of the outer layer with S-orbitals.
Heavy metal - These are osmium (OS) with p \u003d 22.5 g / cm 3 (component of superhard and wear-resistant alloys), the most refractory metal is tungsten W with T \u003d 3420 ° C (used for the manufacture of filaments of lamps), the hardest metal - This is a chrome CR (scratching glass). They are part of the materials from which the metal-cutting tool is manufactured, brake pads of heavy machines, etc. Metals interact differently with a magnetic field. Such metals like iron, cobalt, nickel and gadolinium are highlighted with its ability to magnify. They are called ferromagnets. Most metals (alkaline and alkaline earth metals and a significant part of transition metals) are poorly magnetized and does not retain this state outside the magnetic field - these are paramagnetics. Metals pushed into a magnetic field - diamagnetics (copper, silver, gold, bismuth).
When considering the electronic structure of metals, we divided metals to metals of the main subgroups (S- and P-elements) and metals of side subgroups (transient D- and F-elements).
The technique is customary to classify metals on various physical properties:
1. Density - Lungs (p< 5 г/см 3) и тяжелые (все остальные).
2. Melting temperature - low-melting and refractory.
There are classifications of metals for chemical properties. Metals with low chemical activity are called noble(Silver, Gold, Platinum and its analogs - Osmia, Iridium, Ruthenium, Palladium, Rhodium). In the proximity of chemical properties allocate alkaline(Metals of the main subgroup I group), alkaline earth(calcium, strontium, barium, radium), and rare earth metals(Scandium, Yttria, Lantan and Lantanoids, Actinia and Aktinoids).
General chemical properties of metals
Metal atoms are relatively easy give valence electrons and go to positively charged ions, that is, oxidized. This is the main general property and atoms, and simple substances - metals. Metals in chemical reactions are always reducing agents. The reduction capacity of atoms of simple substances - metals formed by the chemical elements of one period or one main subgroup of the periodic system D. I. Mendeleev varies naturally.
The reductive activity of the metal in chemical reactions that flow in aqueous solutions reflects its position in the electrochemical row of metals voltages.
Based on this series of stresses, we can draw the following important conclusions about the chemical activity of metals in the reactions occurring in aqueous solutions under standard conditions (T \u003d 25 ° C, p \u003d 1 atm).
· The to the left is the metal in this row, the stronger reducing agent it is.
· Each metal is able to exhibit (restore) from salts in solutions. Those metals that are in a row of stresses after it (to the right).
· Metals located in a row of voltage to the left of hydrogen are able to exhibit it from acids in solution
· Metals, which are the strongest reducing agents (alkaline and alkaline earth), interact in any aqueous solutions primarily with water.
The reductive activity of the metal, determined by the electrochemical row, does not always correspond to its position in the periodic system. This is due to the fact that in determining the position of the metal in a row of stresses, not only the energy of the separation of electrons from individual atoms is taken into account, but also the energy spent on the destruction of the crystal lattice, as well as the energy that is emitted during hydration of ions. For example, lithium is more active in aqueous solutions than sodium (although the provision in the periodic system Na is more active metal). The fact is that the hydration energy of Li + ions is much larger than the energy of hydration Na +, so the first process is energetically more profitable. Having considered the general provisions characterizing the rehabilitation properties of metals, we turn to specific chemical reactions.
Metal interaction with non-metals
· With oxygen most metals form oxides- Basic and amphoteric. Acid oxides of transition metals, such as chromium oxide (VI) Cro G or manganese oxide (VII) Mn 2 O 7, are not formed with direct oxidation of metal with oxygen. They are obtained indirectly.
Alkali metals Na, K actively react with air oxygenWhen forming peroxides:
Sodium oxide is obtained indirectly, when calculating peroxides with appropriate metals:
Lithium and alkaline earth metals interact with air oxygen, forming major oxides:
Other metals, except for gold and platinum metals, which are generally not oxidized by air oxygen, interact less actively or when heated:
· With halogens, metals form salts of halogeneous acids, eg:
· With hydrogen the most active metals form hydrides - ionic creeping substances in which hydrogen has a degree of oxidation -1, for example:
Many transition metals form a special type hydride with hydrogen - there is a dissolution or introduction of hydrogen into the crystal lattice of metals between atoms and ions, while the metal retains its appearance, but increases in volume. The absorbed hydrogen is in metal, which is imaginary, in atomic form.
There are also hydrides of intermediate metals.
· With gray metals form salts - sulphides, eg:
· With nitrogen metals react somewhat more difficult, t. K. Chemical connection in the nitrogen molecule N 2 is very strong; At the same time, nitrides are formed. At normal temperature, it interacts with nitrogen only lithium:
Metal interaction with complex substances
· With water. Alkaline and alkaline earth metals under normal conditions displacing hydrogen from the water and form soluble bases - alkali, for example:
Other metals in a row of voltages to hydrogen can also be suppressed by hydrogen from water under certain conditions. But aluminum strictly interacts with water, only if removed from its surface an oxide film:
Magnesium interacts with water only during boiling, and hydrogen is also highlighted:
If the burning magnesium is added to the water, the burning continues, since the reaction flows:
Iron interacts with water only in a rare form:
· With acids in solution (HCl, H 2 SO. 4 ), Ch 3 COOH, etc., except hno 3 ) Metals interact in a row of voltages to hydrogen. At the same time, salt and hydrogen are formed.
But lead (and some other metals), despite its position in a row of stresses (to the left of hydrogen), almost disassembled in dilute sulfuric acid, because the resulting sulfate of lead PBSO 4 insoluble and creates a protective film on the surface of the metal.
· Salts less active metals in solution. As a result of such a reaction, a salt of more active metal is formed and less active metal is distinguished in free form.
It should be remembered that the reaction is in cases where the soluble soluble is formed. The displacement of metals from their compounds by other metals was first studied by N. N. Beketov - the Great Russian scientist in the field of physical chemistry. It has placed metals for chemical activity in the "crucible row", which has become a prototype of a number of voltages of metals.
· With organic substances. Interaction with organic acids is similar to reactions with mineral acids. Alcohols can exhibit weak acidic properties when interacting with alkaline metals:
The phenol reacts similarly:
Metals are involved in halogens reactions, which are used to obtain lower cycloalkanes and for synthesis, during which the carbon skeleton of the molecule (reaction A. Würsts) is complicated:
· With alkalis, metals interact in the solution, the hydroxides of which are amphoterns. For example:
· Metals can form chemical compounds with each other, which received the common name of the intermetallic compounds. They most often do not appear the degrees of oxidation of atoms, which are characteristic of compounds of metals with non-metals. For example:
Cu 3 AU, LANI 5, NA 2 SB, CA 3 SB 2, etc.
Intermetallic compounds usually do not have a constant composition, the chemical bond in them is mainly metallic. The formation of these compounds is more characteristic of metals of side subgroups.
Metals of the main subgroups of I-III groups of the periodic system of chemical elements D. I. Mendeleev
general characteristics
These are metals of the main subgroup I group. Their atoms at the external energy level have one electron. Alkali metals - strong reducing agents. Their reduction capacity and chemical activity increase with an increase in the sequence number of the element (i.e., from top to bottom in the periodic table). All of them possess electronic conductivity. The strength of communication between alkali metal atoms is reduced with an increase in the sequence number of the element. Also reduced their melting and boiling points. Alkali metals interact with many simple substances - oxidifiers. In water reactions, they form soluble bases (alkali) soluble in water. Alkaline earth elements The elements of the main subgroup of group II are called. Atoms of these elements contain in the external energy level two electron. They are strongest reducing agents have a degree of oxidation +2. In this main subgroup, general patterns in changing the physical and chemical properties associated with an increase in the size of atoms over the group from top to bottom are also weakened by the chemical bond between atoms. With an increase in the size of the ion, acidic and the main properties of oxides and hydroxides are enhanced.
The main subgroup of the group III is elements of boron, aluminum, gallium, indium and tall lities. All items belong to P-elements. In the external energy level, they have three (S. 2 p. 1 ) ElectronWhat explains the similarity of the properties. The degree of oxidation is +3. Inside the group with an increase in the charge of the kernel, metal properties increase. Bor - element-nonmetall, and aluminum has already metallic properties. All elements form oxides and hydroxides.
Most metals are in subgroups of the periodic system. In contrast to the elements of the main subgroups, where there is a gradual filling of the electrons of the appearance of atomic orbitals, the elements of side subgroups are filled with D-orbitals of the penultimate energy level and the latter S-orbital. The number of electrons corresponds to the group number. Elements with an equal number of valence electrons enter the group under one number. All elements of subgroups are metals.
Simple substances formed by metals subgroups have durable crystal lattices resistant to heating. These metals are the most durable and refractory among other metals. D-elements are brightly manifested by the transition with an increase in their valence from the main properties through amphoteric to acid.
Alkali metals (Na, K)
At the external energy level, alkali metal atoms of elements contain one electronlocated on a high distance from the kernel. They easily give this electron, so they are strong reducing agents. In all compounds, alkali metals exhibit the degree of oxidation +1. Their rehabilitation properties with increasing radius of atoms are amplified from Li to Cs. All of them are typical metals, have silver-white color, soft (cut by knife), light and low-melting. Actively interact with all nemmetallas:
All alkali metals when reacting with oxygen (elimination LI) form peroxides. In free form, alkali metals are not found due to their high chemical activity.
Oxides. - Solids, have basic properties. They are obtained by calcining peroxides with appropriate metals:
Naoh, KOH hydroxides - Solid white substances, hygroscopic, are well soluble in water with heat release, they are related to alkalis:
Alkali metal salts are almost soluble in water. The most important of them: Na 2 CO 3 - sodium carbonate; Na 2 CO 3 10H 2 O - crystalline soda; NaHCO 3 - sodium bicarbonate, food soda; K 2 CO 3 - potassium carbonate, potash; Na 2 SO 4 10h 2 O - Glauberova Salt; NaCl - sodium chloride, food salt.
Elements of group I in tables
Alkaline earth metals (CA, MG)
Calcium (CA) is a representative alkaline earth metalswhich are called elements of the main subgroup of group II, but not all, but only starting with calcium and down the group. These are the chemical elements that, interacting with water, form alkali. Calcium in the external energy level contains two electrons, oxidation degree +2.
The physical and chemical properties of calcium and its connections are presented in the table.
Magnesium (MG) It has the same structure of an atom as calcium, the degree of its oxidation is also +2. Soft metal, but its surface in air is covered with a protective film that slightly reduces chemical activity. His burning is accompanied by a dazzling outbreak. MGO and MG (OH) 2 show major properties. Although Mg (OH) 2 and a little solisten, but staining the phenolphthalein solution in the raspberry color.
Mg + O 2 \u003d MGO 2
Mo oxides are solid white refractory substances. In the technique of CaO is called negated lime, and MGO - magnesia, these oxides are used in the production of building materials. The reaction of calcium oxide with water is accompanied by the release of heat and is called lime quenching, and the resulting Ca (OH) 2 - hawed lime. A clear solution of calcium hydroxide is called lime water, and white suspension Ca (OH) 2 in water - lime milk.
Magnesium and calcium salts are obtained by reacting them with acids.
Caco 3 - calcium carbonate, chalk, marble, limestone. Used in construction. MGCO 3 - magnesium carbonate - applied in metallurgy for exemption from slags.
Caso 4 2H 2 O - Gypsum. MgSO 4 - magnesium sulfate - is called bitter, or English, salt, contained in sea water. BASO 4 - Barium sulfate - due to insoluability and ability to delay X-rays applied in diagnostics ("Barrit Porridge") of the gastrointestinal tract.
The share of calcium accounts for 1.5% of human body weight, 98% of calcium is contained in the bones. Magnesium is a bio-element, its in the body of a person about 40 g, it is involved in the formation of protein molecules.
Alkaline earth metals in tables
Aluminum
Aluminum (AL) - element of the main subgroup of the group III periodic system D. I. Mendeleev. Aluminum atom contains at the external energy level three electronswhich it easily gives in chemical interactions. The generic team of the subgroup and the upper neighbor of aluminum - boron - the radius of the atom is smaller (in the boron it is 0.080 nm, aluminum is 0.143 nm). In addition, one intermediate eight-electron layer (2e; 8e; 3e) appears at the aluminum atom, which prevents the length of external electrons to the kernel. Therefore, at atoms of aluminum, reducing properties are expressed quite strongly.
Almost all of its compounds aluminum has the degree of oxidation is +3..
Aluminum simple substance
Silver-white light metal. Melts at 660 ° C. Very plastic, it is easily pulled in a wire and rolled in foil thickness to 0.01 mm. It has a very large electrical conductivity and thermal conductivity. Form with other metals light and durable alloys. Aluminum is a very active metal. If the powder of aluminum or thin aluminum foil is strongly heat, then they flammable and burn with dazzling flame:
This reaction can be observed when burning Bengal lights and fireworks. Aluminum, like all metals, easy reacts with non-metals, especially in powder condition. In order to begin the reaction, initial heating must be necessary, with the exception of reactions with halogen - chlorine and bromine, but then all the aluminum reactions with non-metals are very violently and accompanied by the release of a large amount of heat:
Aluminum well dissolved in diluted sulfur and hydrochloric acids:
And here concentrated sulfur and nitric acids pass aluminumforming on the surface of the metal dense durable oxide filmwhich prevents further reaction flow. Therefore, these acids are transported in aluminum tanks.
Oxide and aluminum hydroxide have amphoteric propertiestherefore aluminum dissolves in aqueous solutions by alkali, forming salts - aluminates:
Aluminum is widely used in metallurgy for the production of metals - chromium, manganese, vanadium, titanium, zirconium from their oxides. This method is called alylummith. In practice, the thermite is often used - a mixture of Fe 3 O 4 with aluminum powder. If this mixture is settling, for example, with a magnesium tape, then an energetic reaction occurs with the highlight of a large amount of heat:
The highlighted heat is quite enough to complete the melting of the formed iron, so this process is used for welding steel products.
Aluminum can be obtained by electrolysis - the decomposition of the melt of its al 2 O 3 oxide into components using an electric current. But the melting point of aluminum oxide is about 2050 ° C, so the electrolysis requires high energy costs.
Aluminum compounds
Aluminosilicates. These compounds can be considered as salts formed by alumina, silicon, alkaline and alkaline earth metals. They constitute the bulk of the earth's crust. In particular, aluminosilicates are part of the fields - the most common minerals and clays.
Bauxite- Mountain breed from which aluminum is obtained. It contains Al 2 O 3 alumina.
Corundum- The mineral of the composition Al 2 O 3, has a very high hardness, its fine-grained variety containing impurities - emery, is used as an abrasive (grinding) material. The same formula has another natural connection - alumina.
Well known transparent, painted by impurities, Corundum crystals: Red - rubies and blue - sapphires that use as precious stones. Currently, they are artificially obtained and used not only for jewelry, but also for technical purposes, for example, for the manufacture of details of hours and other accurate devices. Ruby crystals are used in lasers.
Aluminum aluminum oxide 2 O. 3 - White substance with a very high melting point. It can be obtained by decomposition when aluminum hydroxide heating:
Aluminum hydroxide Al (OH) 3 it falls in the form of a student under the action of alkalis for solutions of aluminum salts:
how amphoteric hydroxide It is easily dissolved in acids and alkalis solutions:
Aluminati. Called salts of unstable aluminum acids - orealuminum H 2 ALO 3, metaluminum Halo 2 (it can be considered as an orthoaluminum acid, from which the water molecule was taken away from the molecule). Natural aluminates include a noble spinel and precious chrysoberill. Aluminum salts, in addition to phosphates, are well soluble in water. Some salts (sulphides, sulfites) decompose water. AlCl 3 aluminum chloride is used as a catalyst in the production of very many organic substances.
Elements of group III in tables
Characteristics of transition elements - copper, zinc, chromium, iron
Copper (CU) - element of the side subgroup of the first group. Electronic formula: (... 3D 10 4S 1). The tenth D-electron is mobile, since he moved from 4s-sublevel. Copper in the compounds shows the oxidation degree +1 (Cu 2 O) and +2 (CUO). Copper - metal light pink color, drum, viscous, excellent electricity conductor. Melting point 1083 ° C.
Like other metals subgroups I of the periodic system, copper it is worthwhile to the row of the right of hydrogen and does not displace it from acids, but reacts with oxidizing acids:
Under the action of alkalishes on solutions of copper salts drops the sediment of a weak base of blue- Copper hydroxide (II), which, when heated, decomposes on the main oxide of Cuo black and water:
Chemical properties of copper in tables
Zinc (Zn)- element of a side subgroup of group II. Its electronic formula is as follows: (... 3D 10 4S 2). Since in the zinc atoms, the penultimate D-supeller is fully completed, the zinc in the connections shows the degree of oxidation +2.
Zinc - metal silver-white color, practically not changing in air. It has corrosion resistance, which is explained by the presence of an oxide film on its surface. Zinc - one of the most active metals, at elevated temperature reacts with ordinary substances:
Zinc as other metals huses less active metals from their salts:
Zn + 2AGNO 3 \u003d 2AG + Zn (NO 3) 2
Hydroxide zinc amphoterren, i.e. shows properties and acids, and grounds. With a gradual tide of the alkali solution to a solution of zinc salt, the precipitate was dissolved at first (similarly occurs with aluminum):
Chemical properties of zinc in tables
For example Chromium (CR) You can show that properties of transition elements are changing along the period not fundamentally: A quantitative change occurs, associated with a change in the number of electrons on valence orbital. Maximum degree of chromium oxidation +6. Metal in a row of activity is to the left of hydrogen and displaces it from the acids:
When adding a solution of alkali to such a solution, a precipitate of Me (OH) is formed 2 which is quickly oxidized by air oxygen:
It corresponds to amphoteric oxide CR 2 O 3. Oxide and chromium hydroxide (in the highest oxidation) exhibit the properties of acidic oxides and acids, respectively. Chromic acid salts (H 2 CR O. 4 ) In the acidic environment turn into dichromates - Salts of dichromic acid (H 2 Cr 2 O 7). Chromium compounds have a high oxidative capacity.
Chemical properties of chromium in tables
Iron FE- element of the side subgroup of the VIII group and the 4th period of the Periodic System D. I. Mendeleev. Iron atoms are somewhat different from the atoms of the elements of the main subgroups. As it should be the element of the 4th period, the iron atoms have four energy levels, but not the last, but the penultimate, the third of the nucleus, the level is filled out of them. At the last level, iron atoms contain two electrons. In the penultimate level, which can accommodate 18 electrons, the iron atom has 14 elens. Consequently, the distribution of electrons by levels in iron atoms is such: 2e; 8e; 14e; 2e. Like all metals, iron atoms show rehabilitation properties, giving up with chemical interactions not only two electrons from the last level, and purchasing the degree of oxidation +2, but also an electron from the penultimate level, while the degree of oxidation of the atom rises to +3.
Iron simple substance
This is a silver-white brilliant metal with a melting point of 1539 ° C. Very plastic, so it is easy to handle, goes, rolled, stamps. Iron has the ability to magnify and demagnetize. It can be given greater strength and hardness by methods of thermal and mechanical impact. There are technically clean and chemically pure iron. Technically pure iron, in fact, is a low-carbon steel, it contains 0.02-0.04% carbon, and oxygen, sulfur, nitrogen and phosphorus - even less. Chemically pure iron contains less than 0.01% impurities. Of the technically pure iron are made, for example, stationery clips and buttons. Such iron is easily corroded, while the chemically pure iron is almost not corrosion. Currently, iron is the basis of modern equipment and agricultural engineering, transport and means of communication, spacecraft and in general of the entire modern civilization. Most of the products starting from the sewing needle, and ending with spacecraft cannot be manufactured without the use of iron.
Chemical properties of iron
Iron can show the degree of oxidation +2 and +3Accordingly, iron gives two rows of compounds. The number of electrons that the atom of iron gives in chemical reactions depends on the oxidative ability of substances reacting with it.
For example, with halogens, iron forms halides in which it has a degree of oxidation +3:
and with gray - iron sulphide (II):
Running iron burns in oxygen With the formation of iron scale:
At high temperatures (700-900 ° C) iron reacts with water vapor:
In accordance with the position of iron in an electrochemical row of stresses, it can exhibit metals with the right of it, from aqueous solutions of their salts, for example:
In dilute hydrochloric and sulfuric acids, iron dissolves, i.e. oxidized by hydrogen ions:
Soluble iron and in dilute nitric acidAt the same time, iron (III) nitrate (III) is formed, water and nitric acid recovery products - N 2, NO or NH 3 (NH 4 NO 3) depending on the concentration of the acid.
Jean compounds
In nature, iron forms a number of minerals. This is a magnetic Zheleznyak (magnetite) Fe 3 O 4, Red Zhematte (hematite) Fe 2 O 3, Brown Zhemenyak (Limonite) 2fe 2 O 3 3H 2 O. Another natural iron connection - iron, or sulfur, cchedan (pyrite) fes 2, does not serve as an iron ore to obtain a metal, but is used for the production of sulfuric acid.
For iron, two rows of connections are characteristic: compounds of iron (II) and iron (III).The oxide of iron (II) FEO and the corresponding hydroxide of iron (II) FE (OH) 2 is indirectly, in particular, according to the following chain of transformations:
Both compounds have brightly pronounced basic properties.
Iron Cations (II) Fe 2 + Easily oxidized by air oxygen to iron (III) feed cations 3 + . Therefore, the white precipitate of iron hydroxide (II) acquires green color, and then becomes brown, turning into iron hydroxide (III):
Iron oxide (III) Fe 2 O. 3 and the corresponding iron (III) hydroxide (OH) 3 (OH) 3 also get indirectly, for example, by chain:
Sulfates and chlorides have the greatest technical importance from the salts of iron.
FEESO 4 7H 2 O Sulphate Crystal Hydalline 2 O, known called Iron Camp, is used to combat pests of plants, for the preparation of mineral paints and for other purposes. The chloride of iron (III) FECL 3 is used as a sweat when the tissue is painted. Iron sulfate (III) Fe 2 (SO 4) 3 9H 2 O is used to purify water and for other purposes.
The physical and chemical properties of iron and its connections are summarized in the table:
Chemical properties of iron in tables
Quality reactions to FE 2+ and Fe 3+ ions
To recognize iron (II) compounds and (iii) conduct high-quality reactions to Fe Ions 2+ and Fe. 3+ . A high-quality response to FE 2+ ions is the reaction of iron (II) salts with a compound K 3, called the red blood saline. This is a special group of salts, which are called comprehensive, with them you will get to know later. It is also necessary to assimilate how such salts dissociate:
FE 3+ ions reagent is another complex compound - yellow blood salt - K 4, which dissociates in a solution similarly:
If the solutions containing the FE 2+ and Fe 3+ ions add, respectively, the solutions of the red blood saline (reagent on Fe 2+) and the yellow blood salt (reagent on Fe 3+), then in both cases the same blue precipitate falls:
For the detection of FE 3+ ions, the interaction of iron (III) salts with KNCS rodanide Kncs or ammonium NH 4 NCS is used. At the same time, a brightly colored ion of Fencns 2+ is formed, as a result of which the whole solution acquires intensively red color:
Solubility table
Page 2.
Iron, copper and aluminum have a characteristic metal shine.
Studying solids that do not have a characteristic metal gloss, we notice that their electrical conductivity is very low. These include substances that we call ionic - sodium chloride, calcium chloride, silver nitrate and silver chloride, as well as molecular crystals, such as ice. Ice shown in Fig. 5 - 3 consists of the same molecules that exist in the gas phase, but ordering located in the crystal lattice. These bad electrical current conductors are very different from the metals in almost all properties. Thus, electrical conductivity can be used to classify substances, which is one of the most reasonable.
Metals are called simple crystalline substances having a characteristic metal shine, well conductive heat and electric current capable of changing their shape under the action of external effort and maintain it after removing the load without any signs of destruction. Of the entire number of chemical elements currently known, eighty elements are metals. The most common metals in the earth's crust in the form of chemical compounds are aluminum, iron, magnesium, potassium, sodium and calcium. Clean metals have limited use in the technique, as in nature is extremely rare, and the receipt of them from chemical compounds (ores) is associated with great difficulties.
As a result of hydrogen corrosion, the surface of steel loses the characteristic metal shine and becomes matte.
Polymers are finely dispersed painted powders with characteristic metal glitter, soluble only in concentrated sulfuric acid.
All D - elements are metals with a characteristic metal glitter. Compared to S - metals, their strength is significantly higher.
Unauthorized iodine forms a well-visible film with a characteristic metal glitter (floating on the surface of the solution) or assembled on the bottom of the flask in the form of ferrous particles. Since the solution of the iodine is painted into intensively red and almost not transparent, it is necessary to consider it very carefully, holding a flask against a bright electrical lamp hanging on the ceiling. To do this, you need to stand under the lamp, keeping the flask for the throat in the inclined position between the lamp and face, and try to see a bright image of the lamp in it. On such a background, unattended Iodine crystals are well noticeable. Then the crystals of both substances will gather in one place and around the crystals of the iodine will create a zone of a concentrated solution KJ, in which the iodine will quickly dissolve.
All alkaline metals are silver-white substances, with a characteristic metal glitter, good electricity and thermal conductivity, low melting temperatures and relatively low boiling temperatures, low density and large volume of atoms. In a vapor state of their molecule of monoatoms; ions are colorless.
In appearance dark purple, almost black crystals with a characteristic metal glitter. Well dissolved in water. Mangartageous potassium refers to the number of strong oxidizers than its disinfection properties due.
The peculiarities of the structure of metals are determined by their characteristic physical properties.
Plastic. When deforming (change in the shape of a piece of metal), the ions are only shifted relative to each other, but the rupture does not occur, since their electrons binding their, accordingly, moving around, continue to communicate between mounted ions. In practice, the plasticity manifests itself in the fact that under the blows of the hammer, the metals are not crushed into pieces, and they are flattened - they are forging. The most plastic metal is gold: it can be pulled in thin gold threads, invisible to the human eye or roll into the finest translucent sheets.
Electrical conductivity is explained by electron ability to easily move throughout the piece of metal.
High thermal conductivity is also due to the movement of electrons, since it is precisely they transmit heat into different sections of a piece of metal, due to electrons, metals have characteristic optical properties of opacity and metal glitter. Metals shine because light rays reflect from their surface, and do not let them like glass, and do not absorb them like soot.
Various properties are manifested in metals in an unequal degree. Silver has the best conductivity, the second place on electronic conductivity occupies copper, then aluminum follows. With the help of these metals, you can transmit electrical energy over long distances. But in electrical engineering, aluminum and copper are used as material for wiring, so they are much cheaper than silver.
In the same order, the metals are located on thermal conductivity: silver, copper, aluminum.
Of the more important properties of the metal, it is worth paying attention to density, hardness, strength and melting point. The density of the metal is greater than its relative atomic mass and the smaller the radius of the atom and vice versa. For example, lithium - 534 kg / m 3, and Osmia - 22,500 kg / m 3. Metals with a density below 5000 kg / m 3 are called light: magnesium, aluminum, titanium. Metals with high density: lead, osmium.
Such properties of metals, as durability, hardness and melting point depend on the strength of the metal communication. This connection is particularly strong in heavy metals with a completed penultimate electron layer of the atom: tantalum, tungsten, etc. These metals are distinguished by high hardness and low smowl.
The melting point of metals varies from 39 ° C (mercury) to 3410 ° C (tungsten). Mercury is the only liquid metal.
The hardness of the metals varies widely: alkaline metals are sufficient soft, and SAMA solid metals are not amenable to processing with a file.
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Chemical elements that form in free state simple substances with a metal tie (see chemical bond). Of 110 well-known chemical elements (see a periodic system of chemical elements) 88 - metals and only 22 - non-metals.
Metals such as gold, silver and copper are known to humans from prehistoric times. In the ancient and middle ages believed that there are only 7 metals (gold, silver, copper, tin, lead, iron and mercury). M. V. Lomonosov determined the metal as a "bright body that can be killed" and attributed to metals Gold, silver, copper, tin, iron and lead. A. Lavoisier in the "initial course of chemistry" (1789) already mentioned 17 metals. At the beginning of the XIX century. The discovery of platinum metals followed, then alkaline, alkaline earth and row of others.
The triumph of the periodic law was the discovery of metals predicted on its basis by D. I. Mendeleev, Glisy, Scandia and Germany. In the middle of the XX century With the help of nuclear reactions, transuran elements were obtained - non-natural radioactive metals.
Modern metallurgy receives over 60 metals and based on more than 5000 alloys.
The structure of metals is based on a crystal lattice of positive ions, immersed in dense gas of movable electrons. These electrons compensate for the power of electrical repulsion between positive ions and thereby bind them into solid bodies.
This type of chemical bond is called a metal tie. It led to the most important physical properties of metals: plasticity, electrical conductivity, thermal conductivity, metal shine.
Plasticity is the ability of metals to change the form when they hit, rolled into thin sheets and stretch into wire. In this case, the displacement of atoms and the ions of the crystal lattice occurs, but the relationship between them is not broken, since the electrons forming the links are moved. The plasticity of metals is reduced in a series of AU, AG, SI, SN, PB, Zn, Fe. Gold, for example, can be rolled into sheets with a thickness of up to 0.003 mm, which are used for gilding.
High electrical conductivity of metals is explained by the presence of free electrons, which, under the influence of even a small potential difference, move from the negative pole to the positive. With an increase in the temperature of oscillation of ions and metal atoms, it is enhanced, which makes it difficult to move the electron and thereby leads to a decrease in electrical conductivity. At low temperatures, the oscillatory movement of ions and atoms, on the contrary, is greatly reduced, and the electrical conductivity increases. Near the absolute zero, the electrical resistance of the metals is practically absent. The best electricity conductor is silver, copper, gold, aluminum, iron go behind it. The thermal conductivity of metals is also changed, which is caused by both high mobility of free electrons and the oscillatory movement of ions, due to which the temperature is rapidly aligning the mass of metal. Metal gloss is also associated with the presence of free electrons.
Of the other physical properties of metals, the density, melting point and hardness are of the greatest practical interest. The easiest of metals - lithium (density of 0.53 g / cm3), the hardest - osmium (22.6 g / cm3). Metals with a density less than 5 g / cm3 are called lungs, the rest are heavy. Melted melting temperatures differ very strongly: cesium and gallium can be melted with warm palms, and the melting point of tungsten + 3410 ° C. Under normal conditions, the only liquid metal - mercury. In a vapor state, all metals are single andomic, their crystal lattice is destroyed.
Metals differ in hardness. The hardest of them - chrome - cuts glass, and the wildest - potassium, rubidium and cesium - easily cut into a knife. Strength, melting point and hardness depend on the strength of the metal communication. It is especially large in heavy metals.
In the technique of iron-based alloys, i.e. cast iron, steel, and the guckle itself is called ferrous metals, all other metals are called color. There are other classifications of metals (see Periodic System of Chemical Elements).
The chemical properties of metals are determined by the weak bond of valence electrons with the atom core. Atoms relatively easily give them, turning into positively charged ions. Therefore, metals are good reducing agents. In this, their main and most common chemical property.
Obviously, the metal reducing agents should enter into reactions with different oxidizing agents, among which there may be simple substances (non-metals), acids, salts of less active metals and some other substances. Compounds of oxygen metals are called oxides with halogen halides, with sulfur - sulfides, with nitrogen-nitrides, with phosphorus - phosphide, with carbon - borides, with hydride hydride, etc. Many of these compounds have found important use in the technique.
In the interaction of metals with acid acids, hydrogen ion is H +, which takes an electron from the metal atom:
Mg - 2e - \u003d Mg 2+
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Mg + 2H + \u003d Mg 2+ + H 2
Metals standing in a row of standard electrode potentials (row of stresses) to the left of hydrogen, usually displaced (restore) hydrogen from diluted acids of the NCL or H2SO4 type, and the metal standing with the right of hydrogen, it is not supplanted.
The interaction of metals with aqueous solutions of salts of less active metals can be illustrated by an example:
Zn + Cuso4 \u003d ZnSO4 + Cu
In this case, there is a separation of electrons from the atoms of a more active metal - zinc and the attachment by the ions of less active S2 +. Guided by a number of standard electrode potentials, it can be said that the metal displaces (restores) from the solutions of their salts many of the metals following it.
Active metals (alkaline and alkaline earth) interact with water, which in this case acts as an oxidizing agent.
Metals, hydroxides, which are amphoterns (see amphoterity), as a rule, interact with solutions and acids, and alkalis.
Metals can form chemical connections to each other. Such compounds typically form typical metals with metals with weak metal properties, such as certain sodium compounds with lead:
NA5PB2, NAPB, NA2PB, NA4PB
Connections of some metals with others are the common name of the intermetallic, intermetallic compounds, or metodes.
The considered properties of metals associated with the impact of electrons in chemical reactions are called metal. To varying degrees, all chemical elements possess them. The metal properties are judged by comparing electronegability of elements. This value, expressed in conventional units, characterizes the ability of an atom in the molecule to attract electrons. The relative values \u200b\u200bof the electrical negativeness of the elements are shown in the table. The less electronegativity, the stronger the metallic properties of the elements are expressed.
Atoms contain atoms in the nodes of the crystal lattice of metals. Electrons moving around atoms form "electronic gas" which can freely move in different directions. This property explains high electrical conductivity and thermal conductivity of metals.
Electronic gas reflects almost all light rays. That is why metals are so hot and most often have gray or white. The links between the individual layers of metal are small, which allows you to move these layers under load in different directions (differently - to deform the metal). A unique metal is pure gold. With pure gold forging, you can make a foil thickness 0.002 mm! Such the finest sheet metal is translucent and has a green shade if a look through it on sunlight.
Electrophysical property of metals expressed in its electrical conductivity. It is believed that all metals have a high electrical conductivityThat is, they spend the current well! But this is not the case, and besides, it all depends on the temperature at which the current is measured. Imagine the crystal lattice of the metal, in which the current is transmitted by electron movement. Electrons move from one knot crystalline grille to another. One electron electron from the lattice node is another electron that continues to move towards another grid node, etc. That is, the electrical conductivity also depends on how easily the electrons can move between the lattice nodes. It can be said that the electrical conductivity of the metal depends on the crystalline structure of the grille and the location density in it particles.
The particles in the nodes of the lattice have oscillations, and these oscillations are the greater the higher the temperature of the metal. Such cribs significantly prevent the movement of electrons in the crystal lattice
Thus, the lower the temperature of the metal, the higher its ability to carry out the current!
Hence the concept superconductivitywhich comes in the metal at temperatures close to absolute zero! With absolute zero (-273 0 c), the fluctuations in the particles in the crystal lattice of the metal completely fade!
Electrophysical property of metalsassociated with current passage call temperature coefficient of electrical resistance!
An interesting fact is established that, for example, lead (Pb) and mercury (Hg) at a temperature that is above absolute zero is only a few degrees, the electrical resistance almost completely disappears, that is, the superconductivity condition comes.
The highest electrical conductivity has silver (AG), then copper (CU), then Gold (AU) and aluminum (AL) goes. With high electrical conductivity of these metals, their use in electrical engineering is associated. Sometimes, gold (gilded contacts) is used to provide chemical resistance and anti-corrosion properties.
It should be noted that the electrical conductivity of metals is significantly higher than the electrical conductivity of non-metals. For example, carbon (C - graphite) or silicon (Si) have electrical conductivity of 1000 times less than, for example, mercury. In addition, non-metals, in their majority are not electricity conductors. But among non-metals there are semiconductors: Germanium (GE), silicon crystalline, as well as some oxides, phosphites (metal compounds with phosphorus) and sulfides (metal and sulfur chemical compounds).
You, probably, is familiar to the phenomenon - this property of metals under the action of temperature or light to give electrons.
As for the thermal conductivity of metals, it can be estimated from the Mendeleev table, it is distributed as much as electronegability of metals. (Metals left at the top have the greatest electronenence, for example, sodium electronenence Na is -2.76 B). In terms of queue, the thermal conductivity of metals is explained by the presence of free electrons that carry thermal energy.
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