Metals (from the Latin metallum - mine, mine) - a group of elements in the form of simple substances with characteristic metallic properties , such as high thermal and electrical conductivity , positive temperature coefficient of resistance , high ductility , ductility and metallic luster.
Content
Classification
Of the 118 chemical elements that are open at the moment (so far 127 have been found in total for 2019), metals are often referred to (there is no uniform generally accepted definition, for example, semimetals and semiconductors are not always classified as metals)
6 elements in the group of alkali metals : Li , Na , K , Rb , Cs , Fr ;
4 in the group of alkaline earth metals : Ca , Sr , Ba , Ra ;
as well as outside certain groups, beryllium and magnesium ;
38 in the group of transition metals :
- Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn;
- Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd;
- Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg;
- Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn;
7 in the group of light metals : Al, Ga, In, Sn, Tl, Pb, Bi;
7 in the group of semimetals [1] : B, Si, Ge, As, Sb, Te, Po;
14 in the group of lanthanides + lanthanum (La):
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu;
14 in the actinide group (physical properties are not studied in all elements) + actinium (Ac):
Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr.
Hydrogen may also have metallic properties [2] [3] .
Thus, perhaps 94 elements of all open metals belong to metals; all others are non-metals .
In astrophysics, the term "metal" may have a different meaning and denote all chemical elements heavier than helium (see Metallicity ) .
In addition, in physics, metals as conductors are opposed to semiconductors and dielectrics [4] .
Some groups / families of metals
- Alkaline :
- Lithium
- Sodium
- Potassium
- Rubidium
- Cesium
- Francius
- Alkaline :
- Calcium
- Strontium
- Barium
- Radium
- Others (which are often not quite correctly attributed to alkaline earth):
- Beryllium
- Magnesium
- Transients :
- Uranus
- Titanium
- Iron
- Platinum
- Copper
- Zinc
- Gold
- Silver
- Palladium
- Mercury
- Nickel
- Cobalt
- Tungsten
- Post junction :
- Lungs :
- Aluminum
- Gallium
- Lead
- Tin
- Heavy :
- Lead
- Mercury
- Copper
- Cadmium
- Cobalt
- Lungs :
- Refractory
- Platinum Group Metals
- Colored
- Noble
- Coin operated
Amorphous Metals
The origin of the word "metal"
The word " metal " is borrowed from German . It is noted in the "Travnik" of Nikolai Lubchanin, written in 1534: " ... gold and silver will overcome all the metals ." Finally learned in the era of Peter the Great. Originally had the general meaning of " mineral , ore , metal"; the distinction between these concepts occurred in the epoch of M. V. Lomonosov [5] .
| The metal is called the light body, which can be forged. There are only six such bodies: gold, silver, copper, tin, iron and lead. Separated into high and simple metals; which is the difference that it is not possible to burn high in one fire without the help of other matters, but on the contrary, simple ones turn into ashes through a single force. ... For semimetals arsenic, antimony, bismuth, zinc and mercury are revered.M. V. Lomonosov |
The German word “ metall ” is borrowed from the Latin language , where “ metallum ” is “ mine , metal”. Latin, in turn, is borrowed from Greek ( μεταλλον - “ mine , mine ”). [6]
Being in nature
Most metals are present in nature in the form of ores and compounds. They form oxides , sulfides , carbonates and other chemical compounds. To obtain pure metals and their further application, it is necessary to isolate them from ores and carry out refining. If necessary, carry out doping and other metal processing. The study of this engaged in the science of metallurgy . Metallurgy distinguishes ores of ferrous metals (based on iron ) and non-ferrous (iron does not include, in total about 70 chemical elements). Gold, silver and platinum also belong to precious (noble) metals . In addition, in small quantities they are present in sea water and in living organisms (playing an important role in this).
It is known that the human body is 3% composed of metals [7] . Most of the body contains calcium (in the bones ) and sodium , which acts as an electrolyte in the intercellular fluid and cytoplasm. Magnesium accumulates in the muscles and nervous system , copper in the liver , iron in the blood .
Metal production
Ore preparation
Metals are extracted from the earth in the process of mining . The mined ores are a relatively rich source of essential elements. To determine the presence of ores in the earth's crust , special search methods are used, including exploration and exploration of ore deposits. Ore deposits are developed by open pit or open pit mining and underground mining . Sometimes a combined (open-underground) method is used to develop ore deposits.
After the extraction of ores, they are usually subjected to enrichment . At the same time, one or several useful components are extracted from the initial mineral raw materials - ore concentrate (s), middling products and final tailings . The enrichment processes use the differences of minerals of the useful component and waste rock in density, magnetic susceptibility, wettability, electrical conductivity, grain size, grain shape, chemical properties, etc.
Work with ore
Metals are extracted from mined and enriched ore, as a rule, by chemical or electrolytic reduction. In pyrometallurgy , high temperatures are used to convert ore into metallic raw materials; in hydrometallurgy, water chemistry is used for the same purposes. The methods used depend on the type of metal and the type of contamination.
When a metal ore is an ionic compound of a metal and a non-metal, to extract pure metal, it is usually subjected to smelting — heating with a reducing agent. Many common metals, such as iron , copper , tin , are melted using carbon as a reducing agent. Some metals, such as aluminum and sodium , do not have any economically justifiable reducing agent and are recovered using electrolysis . [8] [9]
Sulfide ores are not improved directly to the production of a pure metal, but are burned in air, with the aim of converting them to oxides.
Physical properties of metals
Hardness
All metals (except mercury and, conditionally, France ) under normal conditions are in a solid state , however, they have different hardness . The table below shows the hardness of some metals on the Mohs scale .
| Hardness | Metal |
|---|---|
| 0.2 | Cesium |
| 0.3 | Rubidium |
| 0.4 | Potassium |
| 0.5 | Sodium |
| 0.6 | Lithium |
| 1.2 | Indium |
| 1.2 | Thallium |
| 1.25 | Barium |
| 1.5 | Strontium |
| 1.5 | Gallium |
| 1.5 | Tin |
| 1.5 | Lead |
| 1.5 | Mercury (TV) |
| 1.75 | Calcium |
| 2.0 | Cadmium |
| 2.25 | Bismuth |
| 2.5 | Magnesium |
| 2.5 | Zinc |
| 2.5 | Lanthanum |
| 2.5 | Silver |
| 2.5 | Gold |
| 2.59 | Yttrium |
| 2.75 | Aluminum |
| 3.0 | Copper |
| 3.0 | Antimony |
| 3.0 | Thorium |
| 3.17 | Scandium |
| 3.5 | Platinum |
| 3.75 | Cobalt |
| 3.75 | Palladium |
| 3.75 | Zirconium |
| 4.0 | Iron |
| 4.0 | Nickel |
| 4.0 | Hafnium |
| 4.0 | Manganese |
| 4.5 | Vanadium |
| 4.5 | Molybdenum |
| 4.5 | Rhodium |
| 4.5 | Titanium |
| 4.75 | Niobium |
| 5.0 | Iridium |
| 5.0 | Ruthenium |
| 5.0 | Tantalum |
| 5.0 | Technetium |
| 5.0 | Chromium |
| 5.5 | Beryllium |
| 5.5 | Osmium |
| 5.5 | Rhenium |
| 6.0 | Tungsten |
| 6.0 | β-Uranus |
Melting point
The melting points of pure metals range from −39 ° C (mercury) to 3410 ° C ( tungsten ). The melting point of most metals (with the exception of alkali) is high, but some metals, such as tin and lead , can melt on a conventional electric or gas stove .
Density
Depending on the density , metals are divided into light (density 0.53 ÷ 5 g / cm ³) and heavy (5 ÷ 22.5 g / cm ³). The lightest metal is lithium (density 0.53 g / cm ³). At present, it is impossible to call the heaviest metal, since the densities of osmium and iridium - the two heaviest metals - are almost equal (about 22.6 g / cm ³ - exactly twice the density of lead), and it is extremely difficult to calculate their exact density: for it needs to completely clean the metals, because any impurities reduce their density.
Plasticity
Most metals are plastic, that is, the metal wire can be bent, and it will not break. This is due to the displacement of the layers of metal atoms without breaking the bond between them. The most plastic are gold, silver and copper . Gold can be made into a foil with a thickness of 0.003 mm, which is used for gilding products. However, not all metals are plastic. Wire made of zinc or tin crunches when bent; during deformation, manganese and bismuth almost do not bend at all, but immediately break . Plasticity also depends on the purity of the metal; so, very pure chromium is very plastic, but contaminated with even minor impurities, becomes brittle and more solid. Some metals, such as gold, silver, lead, aluminum, osmium, can grow together with each other, but it can take decades.
Electrical Conductivity
All metals conduct electricity well; This is due to the presence in their crystal lattices of mobile electrons moving under the action of an electric field . Silver, copper and aluminum have the highest electrical conductivity ; for this reason, the last two metals are most often used as a material for wires . Sodium also has a very high electrical conductivity; in experimental equipment attempts are made to use sodium conductors in the form of thin-walled stainless steel pipes filled with sodium. Due to the low specific weight of sodium, with equal resistance, sodium “wires” are much lighter than copper and even somewhat lighter than aluminum.
Thermal Conductivity
The high thermal conductivity of metals also depends on the mobility of free electrons. Therefore, a series of thermal conductivities is similar to a series of conductivities, and the best conductor of heat, like electricity, is silver. Sodium also finds use as a good conductor of heat; It is widely known, for example, the use of sodium in automobile engine valves to improve their cooling.
The lowest thermal conductivity - in bismuth and mercury.
Color
The color of most metals is about the same - light gray with a bluish tinge. Gold, copper and cesium, respectively, yellow, red and light yellow.
Interaction with simple substances
At the external electronic level, the majority of metals have a small amount of electrons (1-3), therefore, in most reactions they act as reducing agents (that is, they “give away” their electrons).
Reactions with simple substances
- All metals react with oxygen except for gold and platinum metals. The reaction with silver occurs at high temperatures, but silver (II) oxide is practically not formed, since it is thermally unstable. Depending on the metal, there may be oxides , peroxides , perpoxides at the outlet:
- lithium oxide
- sodium peroxide
- potassium peroxide
- sodium peroxide
To get oxide from peroxide, peroxide is reduced by metal:
With medium and low-active metals, the reaction occurs when heated:
- Only the most active metals react with nitrogen, only lithium interacts at room temperature, forming nitrides :
When heated:
- All metals react with sulfur except gold and platinum.
Iron reacts with sulfur when heated to form a sulfide :
- Only the most active metals react with hydrogen, that is, metals of the IA and IIA groups, except for Be. Reactions are carried out when heated, with the formation of hydrides . In reactions, the metal acts as a reducing agent, the degree of hydrogen oxidation is −1:
- Only the most active metals react with carbon. At the same time, acetylides or methanides are formed . Acetylenides in contact with water give acetylene , methanides - methane .
Interaction of acids with metals
Metals react with acids differently. Metals standing in the electrochemical series of metal activity (ERAM) to hydrogen interact with almost all acids.
The interaction of non-oxidizing acids with metals that are in the electric range of metal activity to hydrogen
There is a substitution reaction, which is also redox:
Interaction of concentrated sulfuric acid H 2 SO 4 with metals
Oxidizing acids can interact with metals standing in the EPAM after hydrogen:
A strongly diluted acid reacts with the metal according to the classical scheme:
With increasing acid concentration, various products are formed:
Reactions for nitric acid (HNO 3 )
When interacting with active metals reaction options even more:
Doping
Doping is the introduction to the melt of additional elements that modify the mechanical, physical and chemical properties of the base material.
Electronic structure
All metals have a weak bond of valence electrons ( electrons of an external energy level) with the nucleus . Due to this, the created potential difference in the conductor leads to an avalanche-like motion of electrons (called conduction electrons ) in the crystal lattice . The combination of such electrons is often called electron gas . In addition to electrons, phonons (lattice vibrations) contribute to thermal conductivity. Plasticity is due to the low energy barrier to the movement of dislocations and shear crystallographic planes. Hardness can be explained by a large number of structural defects (interstitial atoms, vacancies , etc.).
Due to the easy recoil of electrons, oxidation of metals is possible, which can lead to corrosion and further degradation of properties. The ability to oxidize can be recognized by a series of metal activities . This fact confirms the need to use metals in combination with other elements ( an alloy , the most important of which is steel ), their alloying and the use of various coatings.
For a more correct description of the electronic properties of metals, it is necessary to use quantum mechanics . In all solids with sufficient symmetry , the energy levels of electrons of individual atoms overlap and form allowed bands , and the zone formed by valence electrons is called the valence band . The weak bond of valence electrons in metals leads to the fact that the valence band in metals is very broad, and all valence electrons are not enough to fill it completely.
The principal feature of such a partially filled band is that even at the minimum applied voltage in the sample, the valence electrons reorganize, that is, the electric current flows.
The same high mobility of electrons leads to a high thermal conductivity, as well as to the ability to mirror the electromagnetic radiation (which gives metals a characteristic luster).
Metal Structure
No metal can be prepared in absolutely clean condition. Technically "pure" metals can contain up to several percent of impurities, and if these impurities are elements with low atomic weight (for example, carbon , nitrogen or oxygen ), then in terms of atomic percentages, the content of these impurities can be very large. The first small amounts of impurities in a metal usually enter the crystal as a solid solution. There are two main types of solid solutions :
- first, when the impurity atoms are much smaller than the solvent metal atoms, the dissolved atoms are located in the lattice of the solvent along interstices, or “voids”. The formation of such solid solutions — solid interstitial solutions — is almost always accompanied by expansion of the solvent lattice, and in the vicinity of each dissolved atom there is a local distortion of the lattice;
- the second, when the impurity and solvent atoms are approximately the same size, a solid substitution solution is formed, in which the atoms of the dissolved element replace the solvent atoms, so that atoms of both types occupy places in the common lattice sites. In such cases, there is also a distorted region around each dissolved atom, and whether the lattice will expand or contract in this case depends on the relative sizes of the solvent and solute atoms [11] .
For most metals, the most important elements that form solid interstitial solutions are hydrogen, boron, carbon, nitrogen, and oxygen. The presence of dislocations always leads to the appearance of abnormally large or small interatomic distances. In the presence of impurities, each dislocation is surrounded by the “atmosphere” of impurity atoms. Impurity atmospheres “fix” dislocations, because as a result of displacement of dislocations, a new configuration with increased energy will be formed. The boundaries between the crystals are also regions with anomalous interatomic distances and, therefore, also dissolve impurity atoms more easily than undistorted regions of the crystals.
As the content of impurities increases, the dissolved atoms also enter the bulk of the crystal, but there is still an excess of impurities along the grain boundaries and around dislocations. When the impurity content exceeds the solubility limit, a new phase appears, which can be either a solute, or an intermediate phase, or a compound. In such cases, the boundaries between the phases may be of two kinds. In the general case, the crystal structure of the impurity particles is too different from the structure of the metal-solvent; therefore, the lattices of the two phases cannot transform into one another, forming a continuous structure. In such cases, layers with an irregular (distorted) structure are formed at the interfaces of the phases. The appearance of free surface energy is associated with the formation of boundaries; however, the strain energy of the solvent lattice is relatively small. In such cases, it is said that these particles are allocated incoherently.
In some cases, the interatomic distances and the crystal structure of the solvent metal and impurity particles are such that some planes can be interconnected, forming a continuous structure. Then they say that the particles of the second phase are allocated coherently and, since the conjugation of the lattices is never absolutely accurate, a strongly stressed region forms around the boundary. In cases where the deformation energy is too high for this, neighboring crystals can be contacted in such a way that, in this case, regions of elastic deformation arise in the boundary layers and dislocations at the interface itself. In such cases, the particles are said to be semi-coherent [12] .
With an increase in temperature due to an increase in the amplitude of atomic oscillations, a lattice defect can form, which is called a vacancy or “hole”. Diffusion of vacancies is one of the mechanisms for the formation of dislocations [13] .
As a rule, metal crystallization occurs by supercooling with the formation of a dendritic structure . As the growth of dendritic crystals in contact, with the formation of various structural defects. In most cases, the metal hardens so that the first batch of crystals contains less impurities than subsequent ones. Therefore, as a rule, impurities concentrate on the grain boundaries, forming stable structures [14] .
Application of metals
Construction Materials
Metals and their alloys are one of the main structural materials of modern civilization. This is determined primarily by their high strength , uniformity and impermeability to liquids and gases . In addition, changing the formulation of the alloys, you can change their properties in very wide limits.
Electrical Materials
Metals are used as good conductors of electricity (copper, aluminum), and as materials with increased resistance for resistors and electric heating elements ( nichrome , etc.).
Tool materials
Metals and their alloys are widely used for the manufacture of tools (their working parts). Basically, these are tool steels and hard alloys . Diamond , boron nitride , and ceramics are also used as tool materials.
The history of the development of ideas about metals
Man's acquaintance with metals began with gold , silver, and copper , that is, metals that are found in a free state on the earth's surface; subsequently they were joined by metals that are widely distributed in nature and are easily separated from their compounds: tin , lead , iron, and mercury . These seven metals were familiar to mankind in ancient times. Among the ancient Egyptian artifacts, there are gold and copper products, which, according to some sources, belong to an epoch that was 3000–4000 years distant from AD. er
By the middle ages, zinc , bismuth , and antimony had already been added to the seven known metals, and arsenic in the early 18th century. From the middle of the 18th century, the number of exposed metals quickly increased and reached 65 at the beginning of the 20th century, and 96 at the beginning of the 21st century.
None of the chemical industries has contributed so much to the development of chemical knowledge, such as the processes associated with the production and processing of metals; the most important moments in the history of chemistry are connected with their history. The properties of metals are so characteristic that already in the earliest epoch gold, silver, copper, lead, tin, iron and mercury constituted one natural group of homogeneous substances, and the concept of "metal" refers to the oldest chemical concepts. However, views on their nature in a more or less definite form appear only in the Middle Ages among the alchemists . True, Aristotle 's ideas about nature: the formation of everything that exists from the four elements (fire, earth, water, and air) already indicated the complexity of metals; but these ideas were too vague and abstract. Alchemists have the concept of the complexity of metals and, as a result of this, the belief in the ability to transform one metal into another, to create them artificially, is the basic concept of their worldview.
Only Lavoisier found out the role of air during combustion and showed that the profit in weight of metals during firing comes from the addition of oxygen from the air to metals, and thus found that the act of burning metals is not disintegration into elements, but, on the contrary, the act of combining, the question of The complexity of the metals was resolved negatively. Metals were classified as simple chemical elements, due to the basic idea of Lavoisier that simple bodies are those from which it was not possible to isolate other bodies. With the creation of a periodic system of chemical elements by Mendeleev, elements of metals took their rightful place in it.
See also
- Steel
- Alloy
- Metallurgy
- Metallicity
- Inorganic substances
Notes
- ↑ Strictly speaking, due to the amphoteric nature of the chemical properties, semimetals ( metalloids ) are a separate group, not referring to either metals or non-metals; To the group of metals they can be attributed only conditionally.
- ↑ Ranga P. Dias, Isaac F. Silvera. Observation of the Wigner-Huntington transition to metallic hydrogen (Eng.) // Science. - 2017-01-26. - P. eaal1579 . - ISSN 1095-9203 0036-8075, 1095-9203 . - DOI : 10.1126 / science.aal1579 .
- ↑ In, Geology . Scientists Have Finally Created Metallic Hydrogen , Geology IN . The date of circulation is January 28, 2017.
- ↑ Metals // Encyclopedic Dictionary of Young Physics. / Comp. V. A. Chuyanov. - M .: Pedagogy, 1984. - p. 165-167 . - 352 s.
- ↑ Lomonosov M.V. Fundamentals of Metallurgy and Mining. - St. Petersburg: Imperial Academy of Sciences, 1763. - 416 p.
- ↑ Etymological dictionary of the Russian language. Issue 10: M / Under the general editorship of A. F. Zhuravlev and N. M. Shansky. - M .: MGU Publishing House, 2007. - 400 p. ISBN 978-5-211-05375-5
- ↑ Yuri Kukshkin. Chemistry around us
- ↑ (English) Los Alamos National Laboratory - Sodium . The appeal date is June 8, 2007. Archived August 4, 2012.
- ↑ (English) Los Alamos National Laboratory - Aluminum . The appeal date is June 8, 2007. Archived August 4, 2012.
- ↑ Cooked A.S. Mineral hardness. - AN USSR, 1963. - p. 197-208. - 304 s.
- ↑ Yum-Rosary, 1965 , p. 92
- ↑ Yum-Rosary, 1965 , p. 93–94.
- ↑ Yum-Rosary, 1965 , p. 97.
- ↑ Yum-Rosary, 1965 , p. 103
Literature
- Vukolov S.P. Metals and Metalloids // Encyclopedic Dictionary of Brockhaus and Efron : in 86 tons (82 tons and 4 extras). - SPb. , 1890-1907.
- Gulyaev A.P. Metallography . - 6th. - M .: Metallurgy, 1986. - 544 p.
- Sheypak A. A. Chapter II. Metallurgy // Technique in its historical development . - 2nd. - M .: MGIU, 2004. - T. II. - pp. 54-108. - 302 s.
- Venetsky S.I. In the world of metals. - M .: Metallurgy, 1982. - 256 p.
- Venetsky S.I. On the Rare and Scattered: Stories about Metals / Preface. A. F. Belova. - M .: Metallurgy, 1980. - 184 p.
- Hume-Rosey V. Introduction to physical metallurgy. - Per. from English V.M. Glazov and S.N. Gorin. - Moscow: Metallurgy, 1965. - 203 p.