Indium(lat. Indium), In, a chemical element of group III periodic system Mendeleev; atomic number 49, atomic mass 114.82; white shiny soft metal. The element consists of a mixture of two isotopes: 113 In (4.33%) and 115 In (95.67%); the last isotope has a very weak β-radioactivity (half-life T ½ = 6 10 14 years).
In 1863, German scientists F. Reich and T. Richter, during a spectroscopic study of zinc blende, discovered new lines in the spectrum belonging to an unknown element. By the bright blue (indigo) color of these lines new element was named India.
Distribution India in nature. Indium is a typical trace element, its average content in the lithosphere is 1.4·10 -5% by weight. During magmatic processes, India is slightly accumulated in granites and other acidic rocks. India's main concentration processes in earth's crust associated with hot aqueous solutions that form hydrothermal deposits. Indium is bound in them with Zn, Sn, Cd, and Pb. Sphalerites, chalcopyrites and cassiterites are enriched in Indium by an average of 100 times (the content is about 1.4·10 -3%). Three minerals of India are known - native Indium, roquesite CuInS 2 and indite In 2 S 4 , but they are all extremely rare. Of practical importance is the accumulation of India in sphalerites (up to 0.1%, sometimes 1%). Enrichment in India is typical for deposits of the Pacific ore belt.
Physical properties India. Crystal cell India is tetragonal face-centered with parameters a = 4.583Å and c= 4.936Å. Atomic radius 1.66Å; ionic radii In 3+ 0.92Å, In + 1.30Å; density 7.362 g/cm 3 . Indium is fusible, its t pl is 156.2 ° C; t bale 2075 °C. Temperature coefficient linear expansion 33 10 -6 (20 °С); specific heat at 0-150°C 234.461 J/(kg K), or 0.056 cal/(g°C); electrical resistivity at 0°C 8.2·10 -8 ohm·m, or 8.2·10 -6 ohm·cm; modulus of elasticity 11 N/m 2 , or 1100 kgf/mm 2 ; Brinell hardness 9 MN / m 2, or 0.9 kgf / mm 2.
Chemical properties of India. In accordance with the electronic configuration of the 4d 10 5s 2 5p 1 atom, indium exhibits valences 1, 2, and 3 (predominantly) in compounds. In air in a solid compact state, indium is stable, but oxidizes at high temperatures, and above 800 ° C it burns with a violet-blue flame, giving oxide In 2 O 3 - yellow crystals, readily soluble in acids. When heated, indium easily combines with halogens, forming soluble halides InCl 3 , InBr 3 , InI 3 . Indium is heated in a stream of HCl to obtain InCl 2 chloride, and when InCl 2 vapor is passed over heated In, InCl is formed. With sulfur, Indium forms sulfides In 2 S 3 , InS; they give compounds InS·In 2 S 3 and 3InS·In 2 S 3 . In water in the presence of oxidizing agents, Indium slowly corrodes from the surface: 4In + 3O 2 + 6H 2 O = 4In(OH) 3 . In acids, Indium is soluble, its normal electrode potential is -0.34 V, and practically insoluble in alkalis. Salts of India are easily hydrolyzed; hydrolysis product - basic salts or hydroxide In(OH) 3 . The latter is highly soluble in acids and poorly in alkali solutions (with the formation of salts - indates): In (OH) 3 + 3KOH = K 3. India connections lower degrees oxidation is rather unstable; halides InHal and black oxide In 2 O are very strong reducing agents.
Getting India. Indium is obtained from waste and intermediate products of zinc, lead and tin production. This raw material contains from thousandths to tenths of a percent India. The extraction of India consists of three main stages: obtaining an enriched product - India concentrate; processing of concentrate to crude metal; refining. In most cases, the feedstock is treated with sulfuric acid and indium is transferred into a solution, from which a concentrate is isolated by hydrolytic precipitation. Rough Indium is isolated mainly by carburizing on zinc or aluminum. Refining is carried out by chemical, electrochemical, distillation and crystal-physical methods.
Application India. Indium and its compounds (for example, InN nitride, InP phosphide, InSb antimonide) are most widely used in semiconductor technology. Indium is used for various anti-corrosion coatings (including bearing coatings). Indium coatings are highly reflective, which is used to make mirrors and reflectors. Certain alloys of indium are of industrial importance, including fusible alloys, solders for gluing glass to metal, and others.
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A chemical element is a collective term that describes a set of atoms of a simple substance, that is, one that cannot be divided into any simpler (according to the structure of their molecules) components. Imagine that you receive a piece of pure iron with a request to split it into hypothetical constituents using any device or method ever invented by chemists. However, you can't do anything, the iron will never be divided into something simpler. A simple substance - iron - corresponds to the chemical element Fe.
Theoretical definition
The experimental fact noted above can be explained using the following definition: a chemical element is an abstract collection of atoms (not molecules!) of the corresponding simple substance, i.e. atoms of the same type. If there were a way to look at each of the individual atoms in the piece of pure iron mentioned above, then they would all be the same - iron atoms. In contrast, a chemical compound, such as iron oxide, always contains at least two different kind atoms: iron atoms and oxygen atoms.
Terms you should know
Atomic mass: the mass of protons, neutrons and electrons that make up an atom of a chemical element.
atomic number: the number of protons in the nucleus of an element's atom.
chemical symbol: a letter or pair of Latin letters representing the designation of the given element.
Chemical compound: a substance that consists of two or more chemical elements combined with each other in a certain proportion.
Metal: An element that loses electrons in chemical reactions with other elements.
Metalloid: An element that reacts sometimes as a metal and sometimes as a non-metal.
Non-metal: an element that tends to gain electrons in chemical reactions with other elements.
Periodic system of chemical elements: a system for classifying chemical elements according to their atomic numbers.
synthetic element: one that is obtained artificially in the laboratory, and usually does not occur in nature.
Natural and synthetic elements
Ninety-two chemical elements occur naturally on Earth. The rest were obtained artificially in laboratories. A synthetic chemical element is typically the product of nuclear reactions in particle accelerators (devices used to increase the speed of subatomic particles such as electrons and protons) or nuclear reactors (devices used to manipulate the energy released in nuclear reactions). The first synthetic element obtained with atomic number 43 was technetium, discovered in 1937 by Italian physicists C. Perrier and E. Segre. Apart from technetium and promethium, all synthetic elements have nuclei larger than those of uranium. The last synthetic element to be named is livermorium (116), and before that was flerovium (114).
Two dozen common and important elements
| Name | Symbol | Percentage of all atoms * | Properties of chemical elements (under normal room conditions) |
|||
| In the Universe | In the earth's crust | In sea water | In the human body |
|||
| Aluminum | Al | - | 6,3 | - | - | Lightweight, silver metal |
| Calcium | Ca | - | 2,1 | - | 0,02 | Included in natural minerals, shells, bones |
| Carbon | FROM | - | - | - | 10,7 | Basis of all living organisms |
| Chlorine | Cl | - | - | 0,3 | - | poisonous gas |
| Copper | Cu | - | - | - | - | Only red metal |
| Gold | Au | - | - | - | - | Only yellow metal |
| Helium | He | 7,1 | - | - | - | Very light gas |
| Hydrogen | H | 92,8 | 2,9 | 66,2 | 60,6 | The lightest of all elements; gas |
| Iodine | I | - | - | - | - | Non-metal; used as an antiseptic |
| Iron | Fe | - | 2,1 | - | - | Magnetic metal; used for the production of iron and steel |
| Lead | Pb | - | - | - | - | Soft, heavy metal |
| Magnesium | mg | - | 2,0 | - | - | Very light metal |
| Mercury | hg | - | - | - | - | Liquid metal; one of two liquid elements |
| Nickel | Ni | - | - | - | - | Corrosion resistant metal; used in coins |
| Nitrogen | N | - | - | - | 2,4 | Gas, the main component of air |
| Oxygen | O | - | 60,1 | 33,1 | 25,7 | Gas, the second important air component |
| Phosphorus | R | - | - | - | 0,1 | Non-metal; important for plants |
| Potassium | To | - | 1.1 | - | - | Metal; important for plants; commonly referred to as "potash" |
* If the value is not specified, then the element is less than 0.1 percent.
Big bang as the root cause of the formation of matter
What chemical element was the very first in the universe? Scientists believe that the answer to this question lies in the stars and the processes by which stars are formed. The universe is believed to have originated at some point in time between 12 and 15 billion years ago. Until this moment, nothing that exists, except for energy, is conceived. But something happened that turned this energy into a huge explosion (the so-called Big Bang). In the next seconds after big bang matter began to form.
The first simplest forms of matter to appear were protons and electrons. Some of them are combined into hydrogen atoms. The latter consists of one proton and one electron; it is the simplest atom that can exist.
Slowly, over long periods of time, hydrogen atoms began to gather together in certain regions of space, forming dense clouds. Hydrogen in these clouds was pulled into compact formations by gravitational forces. Eventually these clouds of hydrogen became dense enough to form stars.
Stars as chemical reactors of new elements
A star is simply a mass of matter that generates the energy of nuclear reactions. The most common of these reactions is the combination of four hydrogen atoms to form one helium atom. As soon as stars began to form, helium became the second element to appear in the universe.
As stars get older, they switch from hydrogen-helium nuclear reactions to other types. In them, helium atoms form carbon atoms. Later carbon atoms form oxygen, neon, sodium and magnesium. Still later, neon and oxygen combine with each other to form magnesium. As these reactions continue, more and more chemical elements are formed.
The first systems of chemical elements
Over 200 years ago, chemists began looking for ways to classify them. In the middle of the nineteenth century, about 50 chemical elements were known. One of the questions that chemists sought to resolve. boiled down to the following: is a chemical element a substance completely different from any other element? Or are some elements related to others in some way? Whether there is a common law that unites them?
Chemists have proposed various systems of chemical elements. So, for example, the English chemist William Prout in 1815 suggested that the atomic masses of all elements are multiples of the mass of the hydrogen atom, if we take it equal to one, that is, they must be integers. At that time, the atomic masses of many elements had already been calculated by J. Dalton in relation to the mass of hydrogen. However, if this is approximately the case for carbon, nitrogen, oxygen, then chlorine with a mass of 35.5 did not fit into this scheme.
The German chemist Johann Wolfgang Dobereiner (1780-1849) showed in 1829 that three elements from the so-called halogen group (chlorine, bromine and iodine) could be classified by their relative atomic masses. The atomic weight of bromine (79.9) turned out to be almost exactly the average of the atomic weights of chlorine (35.5) and iodine (127), namely 35.5 + 127 ÷ 2 = 81.25 (close to 79.9). This was the first approach to the construction of one of the groups of chemical elements. Doberiner discovered two more such triads of elements, but he failed to formulate a general periodic law.
How did the periodic table of chemical elements appear?
Most of the early classification schemes were not very successful. Then, around 1869, almost the same discovery was made by two chemists at almost the same time. Russian chemist Dmitri Mendeleev (1834-1907) and German chemist Julius Lothar Meyer (1830-1895) proposed organizing elements that have similar physical and Chemical properties, into an ordered system of groups, series and periods. At the same time, Mendeleev and Meyer pointed out that the properties of chemical elements are periodically repeated depending on their atomic weights.
Today, Mendeleev is generally considered to be the discoverer periodic law because he took one step that Meyer didn't. When all the elements were located in the periodic table, some gaps appeared in it. Mendeleev predicted that these were sites for elements that had not yet been discovered.
However, he went even further. Mendeleev predicted the properties of these not yet discovered elements. He knew where they were located on the periodic table, so he could predict their properties. Remarkably, every chemical element Mendeleev predicted, the future gallium, scandium, and germanium, were discovered less than ten years after he published his periodic law.
Short form of the periodic table
There were attempts to calculate how many variants of the graphic representation of the periodic system were proposed by different scientists. It turned out that more than 500. Moreover, 80% total number options are tables and the rest is geometric figures, mathematical curves, etc. As a result, four types of tables found practical application: short, semi-long, long and ladder (pyramidal). The latter was proposed by the great physicist N. Bohr.
The figure below shows the short form.
In it, the chemical elements are arranged in ascending order of their atomic numbers from left to right and from top to bottom. So, the first chemical element of the periodic table, hydrogen, has atomic number 1 because the nuclei of hydrogen atoms contain one and only one proton. Similarly, oxygen has an atomic number of 8, since the nuclei of all oxygen atoms contain 8 protons (see the figure below).
The main structural fragments of the periodic system are periods and groups of elements. In six periods, all cells are filled, the seventh is not yet completed (elements 113, 115, 117 and 118, although synthesized in laboratories, have not yet been officially registered and do not have names).
Groups are divided into main (A) and secondary (B) subgroups. The elements of the first three periods, containing one series-line each, are included exclusively in A-subgroups. The remaining four periods include two rows each.
Chemical elements in the same group tend to have similar chemical properties. So, the first group consists of alkali metals, the second - alkaline earth. Elements in the same period have properties that slowly change from an alkali metal to a noble gas. The figure below shows how one of the properties - atomic radius - changes for individual elements in the table.
Long period form of the periodic table
It is shown in the figure below and is divided in two directions, by rows and by columns. There are seven period rows, as in the short form, and 18 columns, called groups or families. In fact, the increase in the number of groups from 8 in short form to 18 in long form is obtained by placing all elements in periods starting from the 4th, not in two, but in one line.
Two different systems numbering is used for groups, as shown at the top of the table. The Roman numeral system (IA, IIA, IIB, IVB, etc.) has traditionally been popular in the US. Another system (1, 2, 3, 4, etc.) is traditionally used in Europe, and was recommended for use in the USA a few years ago.
View periodic tables in the figures above is a little misleading, as in any such published table. The reason for this is that the two groups of elements shown at the bottom of the tables should actually be located within them. The lanthanides, for example, belong to period 6 between barium (56) and hafnium (72). In addition, the actinides belong to period 7 between radium (88) and rutherfordium (104). If they were pasted into a table, it would be too wide to fit on a piece of paper or a wall chart. Therefore, it is customary to place these elements at the bottom of the table.
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Terminology 1: : dw Number of the day of the week. "1" corresponds to Monday Term definitions from various documents: dw DUT The difference between Moscow and UTC, expressed as an integer number of hours Term definitions from ... ... Dictionary-reference book of terms of normative and technical documentation
A lot of different things and objects, living and inanimate bodies of nature surround us. And they all have their own composition, structure, properties. In living beings, the most complex biochemical reactions occur that accompany the processes of vital activity. Non-living bodies perform various functions in nature and biomass life and have a complex molecular and atomic composition.
But all together the objects of the planet have common feature: they consist of many tiny structural particles called atoms of chemical elements. So small that they can't be seen with the naked eye. What are chemical elements? What characteristics do they have and how did you know about their existence? Let's try to figure it out.
The concept of chemical elements
In the conventional sense, chemical elements are just a graphic representation of atoms. The particles that make up everything that exists in the universe. That is, the question "what are chemical elements" can be given such an answer. These are complex small structures, collections of all isotopes of atoms, united by a common name, having their own graphic designation (symbol).
To date, 118 elements are known that are discovered both in natural conditions and synthetically, through the implementation of nuclear reactions and the nuclei of other atoms. Each of them has a set of characteristics, its location in common system, history of discovery and name, and also plays a certain role in the nature and life of living beings. Chemistry is the study of these features. Chemical elements are the basis for building molecules, simple and complex compounds, and, consequently, chemical interactions.
Discovery history
The very understanding of what chemical elements are came only in the 17th century thanks to the work of Boyle. It was he who first spoke about this concept and gave it the following definition. These are indivisible small simple substances that make up everything around, including all complex ones.
Prior to this work, the views of alchemists dominated, recognizing the theory of the four elements - Empidocles and Aristotle, as well as those who discovered "combustible principles" (sulfur) and "metallic principles" (mercury).
For almost the entire 18th century, the completely erroneous theory of phlogiston was widespread. However, already at the end of this period, Antoine Laurent Lavoisier proves that it is untenable. He repeats Boyle's formulation, but at the same time supplements it with the first attempt to systematize all the elements known at that time, dividing them into four groups: metals, radicals, earths, non-metals.
The next big step in understanding what the chemical elements are comes from Dalton. He is credited with the discovery of atomic mass. Based on this, he distributes a part of the known chemical elements in the order of increasing their atomic mass.
The steadily intensive development of science and technology makes it possible to make a number of discoveries of new elements in the composition of natural bodies. Therefore, by 1869 - the time of the great creation of D. I. Mendeleev - science became aware of the existence of 63 elements. The work of the Russian scientist became the first complete and forever fixed classification of these particles.
The structure of chemical elements at that time was not established. It was believed that the atom is indivisible, that it is the smallest unit. With the discovery of the phenomenon of radioactivity, it was proved that it is divided into structural parts. Almost everyone at the same time exists in the form of several natural isotopes (similar particles, but with a different number of neutron structures, from which the atomic mass changes). Thus, by the middle of the last century, it was possible to achieve order in the definition of the concept of a chemical element.
Mendeleev's system of chemical elements
The scientist put the difference in atomic mass as the basis and managed to arrange in an ingenious way all known chemical elements in ascending order. However, the whole depth and genius of his scientific thinking and foresight lay in the fact that Mendeleev left empty spaces in his system, open cells for still unknown elements, which, according to the scientist, will be discovered in the future.
And everything turned out exactly as he said. The chemical elements of Mendeleev filled all the empty cells over time. Every structure predicted by scientists has been discovered. And now we can safely say that the system of chemical elements is represented by 118 units. True, three latest discoveries not yet officially confirmed.
The system of chemical elements itself is displayed graphically by a table in which the elements are arranged according to the hierarchy of their properties, the charges of the nuclei and the structural features of the electron shells of their atoms. So, there are periods (7 pieces) - horizontal rows, groups (8 pieces) - vertical, subgroups (main and secondary within each group). Most often, two rows of families are placed separately in the lower layers of the table - lanthanides and actinides.
The atomic mass of an element is made up of protons and neutrons, the totality of which is called the "mass number". The number of protons is determined very simply - it is equal to the ordinal number of the element in the system. And since the atom as a whole is an electrically neutral system, that is, it has no charge at all, the number of negative electrons is always equal to the number of positive proton particles.
Thus, the characteristics of a chemical element can be given by its position in the periodic system. Indeed, almost everything is described in a cell: the serial number, which means electrons and protons, atomic mass (the average value of all existing isotopes of a given element). It can be seen in which period the structure is located (which means that so many layers will have electrons). It is also possible to predict the number of negative particles at the last energy level for the elements of the main subgroups - it is equal to the number of the group in which the element is located.
The number of neutrons can be calculated by subtracting protons from the mass number, that is, the serial number. Thus, it is possible to obtain and compose a whole electron-graphic formula for each chemical element, which will accurately reflect its structure and show possible and manifested properties.
Distribution of elements in nature
A whole science, cosmochemistry, is engaged in the study of this issue. The data show that the distribution of elements on our planet repeats the same patterns in the universe. The main source of nuclei of light, heavy and medium atoms are nuclear reactions occurring in the interior of stars - nucleosynthesis. Thanks to these processes, the Universe and outer space have supplied our planet with all the available chemical elements.
In total, out of the known 118 representatives in natural sources, 89 were discovered by people. These are the fundamental, most common atoms. Chemical elements have also been synthesized artificially by bombarding nuclei with neutrons (nucleosynthesis in the laboratory).
The most numerous are simple substances of such elements as nitrogen, oxygen, hydrogen. Carbon is included in all organic matter, which means that it also occupies a leading position.
Classification according to the electronic structure of atoms
One of the most common classifications of all the chemical elements of a system is their distribution based on their electronic structure. According to how many energy levels are included in the shell of an atom and which of them contains the last valence electrons, four groups of elements can be distinguished.
S-elements
These are those in which the s-orbital is filled last. This family includes elements of the first group of the main subgroup (or Only one electron at the outer level determines the similar properties of these representatives as strong reducing agents.
R-elements
Only 30 pieces. Valence electrons are located at the p-sublevel. These are the elements that form the main subgroups from the third to the eighth group, related to 3,4,5,6 periods. Among them, according to their properties, both metals and typical non-metallic elements are found.
d-elements and f-elements
These are transition metals from 4 to 7 large period. There are 32 elements in total. Simple substances can exhibit both acidic and basic properties (oxidizing and reducing). Also amphoteric, that is, dual.
The f-family includes lanthanides and actinides, in which the last electrons are located in f-orbitals.
Substances formed by elements: simple
Also, all classes of chemical elements can exist in the form of simple or complex compounds. So, it is customary to consider simple those that are formed from the same structure in different amount. For example, O 2 is oxygen or dioxygen, and O 3 is ozone. This phenomenon is called allotropy.
Simple chemical elements that form compounds of the same name are characteristic of each representative of the periodic system. But not all of them are the same in terms of their properties. So, there are simple substances metals and non-metals. The first form the main subgroups with group 1-3 and all secondary subgroups in the table. Non-metals form the main subgroups of 4-7 groups. The eighth main includes special elements - noble or inert gases.
Among all open to date simple elements 11 gases are known under normal conditions, 2 liquid substances (bromine and mercury), all the rest are solid.
Complex connections
It is customary to refer to those that consist of two or more chemical elements. There are plenty of examples, chemical compounds over 2 million are known! These are salts, oxides, bases and acids, complex complex compounds, all organic substances.
