What are chemical elements? System and characteristics of chemical elements. Alphabetical list of chemical elements Chemical elements list

Indium(lat. Indium), In, chemical element of group III of the periodic system of 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 latter isotope has 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. Based on the bright blue (indigo) color of these lines, the new element was named indium.

Distribution of India in nature. Indium is a typical trace element; its average content in the lithosphere is 1.4·10 -5% by mass. During magmatic processes, a slight accumulation of indium occurs in granites and other acidic rocks. The main processes of Indian concentration in the earth's crust are associated with hot aqueous solutions that form hydrothermal deposits. Indium is associated with Zn, Sn, Cd and Pb. Sphalerites, chalcopyrites and cassiterites are enriched in Indium on average 100 times (content about l.4·10 -3%). Three minerals of India are known - native Indium, roquesite CuInS 2 and indite In 2 S 4, but all of them are extremely rare. The accumulation of India in sphalerites (up to 0.1%, sometimes 1%) is of practical importance. Enrichment of India is typical for deposits of the Pacific ore belt.

Physical properties India. The crystal lattice of 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/cm3. Indium is fusible, its melting point is 156.2 °C; boiling point 2075 °C. Temperature coefficient of linear expansion 33·10 -6 (20 °C); specific heat capacity 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; elastic modulus 11 n/m 2, or 1100 kgf/mm 2; Brinell hardness 9 Mn/m 2, or 0.9 kgf/mm 2.

Chemical properties India. In accordance with the electronic configuration of the atom 4d 10 5s 2 5p 1 Indium in compounds exhibits valency 1, 2 and 3 (predominantly). 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 In 2 O 3 oxide - yellow crystals, highly soluble in acids. When heated, indium easily combines with halogens, forming soluble halides InCl 3, InBr 3, InI 3. By heating India in a stream of HCl, InCl 2 chloride is obtained, 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 the 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. Indium is soluble in acids, its normal electrode potential is -0.34 V, and practically insoluble in alkalis. India salts are easily hydrolyzed; hydrolysis product - basic salts or hydroxide In(OH) 3. The latter is highly soluble in acids and poorly soluble in alkali solutions (with the formation of salts - indates): In(OH) 3 + 3KOH = K 3. Indium compounds of lower oxidation states are quite unstable; halides InHal and black oxide In 2 O are very strong reducing agents.

Receipt India. Indium is obtained from waste and intermediate products from the production of zinc, lead and tin. This raw material contains from thousandths to tenths of a percent India. 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 the indium is transferred into solution, from which the concentrate is isolated by hydrolytic precipitation. Rough indium is isolated mainly by cementation on zinc or aluminum. Refining is carried out by chemical, electrochemical, distillation and crystallophysical 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 have high reflectivity, which is used to make mirrors and reflectors. Some indium alloys are of industrial importance, including low-melting alloys, solders for gluing glass to metal, and others.

See also: List of chemical elements by atomic number and Alphabetical list of chemical elements Contents 1 Symbols currently used ... Wikipedia

See also: List of chemical elements by symbol and Alphabetical list of chemical elements This is a list of chemical elements arranged in order of increasing atomic number. The table shows the name of the element, symbol, group and period in... ... Wikipedia

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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, complex biochemical reactions occur that accompany vital processes. Nonliving 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 a common feature: they consist of many tiny structural particles called atoms of chemical elements. So small that they cannot 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.

Concept of chemical elements

In the generally accepted understanding, chemical elements are just a graphical representation of atoms. The particles that make up everything that exists in the Universe. That is, the following answer can be given to the question “what are chemical elements”. 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 to be discovered both naturally and synthetically, through nuclear reactions and the nuclei of other atoms. Each of them has a set of characteristics, its location in the overall system, history of discovery and name, and also plays a specific role in nature and the life of living beings. The science of chemistry studies these features. Chemical elements are the basis for building molecules, simple and complex compounds, and therefore chemical interactions.

History of discovery

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 from which everything around is composed, including all complex ones.

Before this work, the dominant views of alchemists were those who recognized the theory of the four elements - Empidocles and Aristotle, as well as those who discovered “combustible principles” (sulfur) and “metallic principles” (mercury).

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 elements known at that time, dividing them into four groups: metals, radicals, earths, non-metals.

The next big step in understanding what chemical elements are comes from Dalton. He is credited with the discovery of atomic mass. Based on this, he distributes some of the known chemical elements in order of increasing atomic mass.

The steadily intensive development of science and technology allows us 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 established classification of these particles.

The structure of the chemical elements was not established at that time. It was believed that the atom was indivisible, that it was the smallest unit. With the discovery of the phenomenon of radioactivity, it was proven that it is divided into structural parts. Almost everyone exists in the form of several natural isotopes (similar particles, but with a different number of neutron structures, which changes the atomic mass). 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 based it on the difference in atomic mass and managed to ingeniously arrange all the known chemical elements in increasing 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. Mendeleev's chemical elements filled all the empty cells over time. Every structure predicted by the scientist was discovered. And now we can safely say that the system of chemical elements is represented by 118 units. True, the last three discoveries have not yet been officially confirmed.

The system of chemical elements itself is displayed graphically in a table in which the elements are arranged according to the hierarchy of their properties, nuclear charges and structural features of the electronic 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 combination of which is called the “mass number”. The number of protons is determined very simply - it is equal to the atomic number of the element in the system. And since the atom as a whole is an electrically neutral system, that is, having 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 table. After all, almost everything is described in the cell: the serial number, which means electrons and protons, atomic mass (the average value of all existing isotopes of a given element). You can see in which period the structure is located (this means that electrons will be located on so many layers). It is also possible to predict the number of negative particles at the last energy level for 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 atomic number. Thus, it is possible to obtain and compile an entire electron-graphic formula for each chemical element, which will accurately reflect its structure and show the possible and manifested properties.

Distribution of elements in nature

An entire science is studying this issue - cosmochemistry. The data shows that the distribution of elements across our planet follows 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 provided our planet with all available chemical elements.

In total, of the known 118 representatives in natural sources, 89 have been discovered by people. These are the fundamental, most common atoms. Chemical elements were also synthesized artificially by bombarding nuclei with neutrons (laboratory nucleosynthesis).

The most numerous are the simple substances of elements such as nitrogen, oxygen, and hydrogen. Carbon is part of all organic substances, which means it also occupies a leading position.

Classification according to the electronic structure of atoms

One of the most common classifications of all chemical elements of a system is their distribution based on their electronic structure. Based on 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 the last to be filled. This family includes elements of the first group of the main subgroup (or Just one electron at the outer level determines the similar properties of these representatives as strong reducing agents.

P-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, belonging to periods 3,4,5,6. Among them, the properties include both metals and typical non-metallic elements.

d-elements and f-elements

These are transition metals from the 4th to 7th major periods. 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. Thus, simple ones are considered to be those that are formed from the same structure in different quantities. 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 table. But not all of them are the same in their properties. So, there are simple substances, metals and non-metals. The first form the main subgroups with 1-3 groups and all the secondary subgroups in the table. Non-metals form the main subgroups of groups 4-7. The eighth main element includes special elements - noble or inert gases.

Among all the simple elements discovered to date, 11 gases, 2 liquid substances (bromine and mercury), and all the rest are solids are known under ordinary conditions.

Complex connections

These include everything that consists of two or more chemical elements. There are plenty of examples, because more than 2 million chemical compounds are known! These are salts, oxides, bases and acids, complex compounds, all organic substances.

See also: List of chemical elements by atomic number and Alphabetical list of chemical elements Contents 1 Symbols currently used ... Wikipedia

See also: List of chemical elements by symbol and Alphabetical list of chemical elements This is a list of chemical elements arranged in order of increasing atomic number. The table shows the name of the element, symbol, group and period in... ... Wikipedia

Main article: Lists of chemical elements Contents 1 Electronic configuration 2 References 2.1 NIST ... Wikipedia

Main article: Lists of chemical elements No. Symbol Name Mohs hardness Vickers hardness (GPa) Brinnell hardness (GPa) 3 Li Lithium 0.6 4 Be Beryllium 5.5 1.67 0.6 5 B Boron 9.5 49 6 C Carbon 1.5 (graphite) 6...Wikipedia

See also: List of chemical elements by atomic number and List of chemical elements by symbol Alphabetical list of chemical elements. Nitrogen N Actinium Ac Aluminum Al Americium Am Argon Ar Astatine At ... Wikipedia

Main article: Lists of chemical elements No. Symbol Russian name Latin name Etymology of the name 1 H Hydrogen Hydrogenium From other Greek. ὕδωρ “water” and γεννάω “I give birth.” 2 ... Wikipedia

List of symbols of chemical elements are symbols (signs), codes or abbreviations used for a brief or visual representation of the names of chemical elements and simple substances of the same name. First of all, these are symbols of chemical elements ... Wikipedia

Below are the names of erroneously discovered chemical elements (indicating the authors and dates of discovery). All of the elements mentioned below were discovered as a result of experiments carried out more or less objectively, but usually incorrectly... ... Wikipedia

Recommended values ​​for many element properties, along with various references, are collected on these pages. Any changes in the values ​​​​in the infobox must be compared with the given values ​​​​and / or given accordingly ... ... Wikipedia

Chemical symbol of a diatomic chlorine molecule 35 Symbols of chemical elements (chemical symbols) symbol of chemical elements. Together with chemical formulas, diagrams and equations of chemical reactions they form a formal language... ... Wikipedia

Books

• English for doctors. 8th ed. , Muraveyskaya Marianna Stepanovna, Orlova Larisa Konstantinovna, 384 pp. The purpose of the textbook is to teach reading and translating English medical texts, conducting conversations in various areas of medicine. It consists of a brief introductory phonetic and... Category: Textbooks for universities Publisher: Flinta, Manufacturer: Flinta,
• English for doctors, Muraveyskaya M.S. The purpose of the textbook is to teach reading and translating English medical texts, and conducting conversations in various areas of medicine. It consists of a brief introductory phonetic and basic… Category: Textbooks and tutorials Series: Publisher: Flinta,

A chemical element is a collective term that describes a collection 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 being given a piece of pure iron and being asked to separate it into its 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 was a way to look at each of the individual atoms in the piece of pure iron mentioned above, then they would all be iron atoms. In contrast, a chemical compound such as iron oxide always contains at least two different kinds of 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 a 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 seeks to gain electrons in chemical reactions with other elements.

Periodic Table of Chemical Elements: A system for classifying chemical elements according to their atomic numbers.

Synthetic element: One that is produced artificially in a laboratory and is generally not found 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 control the energy released by nuclear reactions). The first synthetic element 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 uranium. The last synthetic chemical element to receive its name is livermorium (116), and before it was flerovium (114).

Two dozen common and important elements

* If the value is not specified, then the element is less than 0.1 percent.

The Big Bang as the root cause of matter formation

What chemical element was the very first in the Universe? Scientists believe the answer to this question lies in stars and the processes by which stars are formed. The universe is believed to have come into being at some point in time between 12 and 15 billion years ago. Until this moment, nothing existing except energy is thought of. But something happened that turned this energy into a huge explosion (the so-called Big Bang). In the next seconds after the Big Bang, matter began to form.

The first simplest forms of matter to appear were protons and electrons. Some of them combine to form 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 cluster together in certain areas of space, forming dense clouds. The 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 energy from nuclear reactions. The most common of these reactions involves the combination of four hydrogen atoms forming one helium atom. Once 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. Later still, 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

More than 200 years ago, chemists began to look for ways to classify them. In the mid-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 some elements related to others in some way? Is there a general law that unites them?

Chemists proposed various systems of chemical elements. 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 unity, i.e. 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, and 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 of 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 constructing one of the groups of chemical elements. Dobereiner discovered two more such triads of elements, but he was unable 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 periodically repeat depending on their atomic weights.

Today, Mendeleev is generally considered the discoverer of the periodic law because he took one step that Meyer did not. When all the elements were arranged in the periodic table, some gaps appeared. Mendeleev predicted that these were places 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, gallium, scandium, and germanium, was discovered less than ten years after he published his periodic law.

Short form of the periodic table

There have been attempts to count how many options for the graphic representation of the periodic table were proposed by different scientists. It turned out that there were more than 500. Moreover, 80% of the total number of options are tables, and the rest are 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 picture below shows the short form.

In it, chemical elements are arranged in ascending order of their atomic numbers from left to right and from top to bottom. Thus, 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. Likewise, oxygen has atomic number 8 since the nuclei of all oxygen atoms contain 8 protons (see 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).

The groups are divided into main (A) and secondary (B) subgroups. Elements of the first three periods, each containing one row, are included exclusively in the A-subgroups. The remaining four periods include two rows.

Chemical elements in the same group tend to have similar chemical properties. Thus, the first group consists of alkali metals, the second - alkaline earth metals. 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, rows and 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 the short form to 18 in the long form is obtained by placing all the elements in periods, starting from the 4th, not in two, but in one line.

Two different numbering systems are 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 United States. Another system (1, 2, 3, 4, etc.) is traditionally used in Europe and was recommended for use in the USA several years ago.

The appearance of the periodic tables in the figures above is a little misleading, as with 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). Additionally, actinides belong to period 7 between radium (88) and rutherfordium (104). If they were inserted into a table, it would become 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.