Knowing the wording periodic law and using the periodic system of elements of D.I. Mendeleev, it is possible to characterize any chemical element and its compounds. It is convenient to put together such a characteristic of a chemical element according to plan.

I. Symbol of a chemical element and its name.

II. The position of a chemical element in the periodic table of elements D.I. Mendeleev:

1. serial number;
2. period number;
3. group number;
4. subgroup (main or secondary).

III. Structure of an atom of a chemical element:

1. charge of the nucleus of an atom;
2. relative atomic mass of a chemical element;
3. number of protons;
4. number of electrons;
5. number of neutrons;
6. number of electronic levels in an atom.

IV. Electronic and electron-graphic formulas of an atom, its valence electrons.

V. Type of chemical element (metal or non-metal, s-, p-, d- or f-element).

VI. Formulas of the highest oxide and hydroxide of a chemical element, characteristics of their properties (basic, acidic or amphoteric).

VII. Comparison of metallic or non-metallic properties of a chemical element with the properties of neighboring elements by period and subgroup.

VIII. The maximum and minimum oxidation state of an atom.

For example, we will provide a description of a chemical element with serial number 15 and its compounds according to their position in D.I. Mendeleev’s periodic table of elements and the structure of the atom.

I. We find in D.I. Mendeleev’s table a cell with the number of a chemical element, write down its symbol and name.

Chemical element number 15 is Phosphorus. Its symbol is R.

II. Let us characterize the position of the element in D.I. Mendeleev’s table (period number, group, type of subgroup).

Phosphorus is found in main subgroup Group V, in the 3rd period.

III. We will provide general characteristics composition of an atom of a chemical element (nuclear charge, atomic mass, number of protons, neutrons, electrons and electronic levels).

The nuclear charge of the phosphorus atom is +15. The relative atomic mass of phosphorus is 31. The nucleus of an atom contains 15 protons and 16 neutrons (31 - 15 = 16). The phosphorus atom has three energy levels containing 15 electrons.

IV. We compose the electronic and electron-graphic formulas of the atom, marking its valence electrons.

The electronic formula of the phosphorus atom is: 15 P 1s 2 2s 2 2p 6 3s 2 3p 3.

Electronic graphic formula for the external level of a phosphorus atom: on the third energy level, on the 3s sublevel, there are two electrons (two arrows in the opposite direction are written in one cell), on three p-sublevels there are three electrons (one is written in each of the three cells arrows having the same direction).

Valence electrons are electrons of the outer level, i.e. 3s2 3p3 electrons.

V. Determine the type of chemical element (metal or non-metal, s-, p-, d- or f-element).

Phosphorus is a non-metal. Since the latter sublevel in the phosphorus atom, which is filled with electrons, is the p-sublevel, Phosphorus belongs to the family of p-elements.

VI. We compose formulas of higher oxide and hydroxide of phosphorus and characterize their properties (basic, acidic or amphoteric).

Higher phosphorus oxide P 2 O 5 exhibits properties acid oxide. Hydroxide corresponding higher oxide, H 3 PO 4, exhibits the properties of an acid. Let us confirm these properties with equations of the types of chemical reactions:

P 2 O 5 + 3 Na 2 O = 2Na 3 PO 4

H 3 PO 4 + 3NaOH = Na 3 PO 4 + 3H 2 O

VII. Let's compare the non-metallic properties of phosphorus with the properties of neighboring elements by period and subgroup.

Phosphorus' subgroup neighbor is nitrogen. Phosphorus' period neighbors are silicon and sulfur. Nonmetallic properties of atoms chemical elements the main subgroups with increasing serial number increase in periods and decrease in groups. Therefore, the non-metallic properties of phosphorus are more pronounced than those of silicon and less pronounced than those of nitrogen and sulfur.

VIII. We determine the maximum and minimum oxidation state of the phosphorus atom.

The maximum positive oxidation state for chemical elements of the main subgroups is equal to the group number. Phosphorus is in the main subgroup of the fifth group, so the maximum oxidation state of phosphorus is +5.

The minimum oxidation state for nonmetals in most cases is the difference between the group number and the number eight. Thus, the minimum oxidation state of phosphorus is -3.

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Zalesov Alexander Kirillovich

Chemical element - element elementum - element, independent part, which is the basis of something, such as a system or set.

Chemical element - etymology

The Latin word elementum was used by ancient authors (Cicero, Ovid, Horace), and in almost the same sense as now - as part of something (speech, education, etc.).

An ancient saying said: “Words are made of letters, bodies are made of elements.” Hence - one of the possible origins of this word - by the name of a number of consonants Latin letters L, M, N (el-em-en).

Mikhail Vasilyevich Lomonosov called atoms elements.

A chemical element is a set of atoms with the same nuclear charge, number of protons, coinciding with the serial or atomic number in the periodic table. Each chemical element has its own name and symbol, which are given in the Periodic Table of the Elements by Dmitry Ivanovich Mendeleev.

The form of existence of chemical elements in free form are simple substances (single element)

History of the concept
The word element (Latin elementum) was used in antiquity (Cicero, Ovid, Horace) as part of something (an element of speech, an element of education, etc.). In ancient times there was a common saying: “Just as words are made up of letters, so bodies are made up of elements.” Hence the probable origin of this word: from the name of a series of consonant letters in Latin alphabet: l, m, n, t (“el” - “em” - “en” - “tum”).

At the international congress of chemists in Karlsruhe (Germany) in 1860, definitions of the concepts of molecule and atom were adopted.

A chemical element (from the point of view of atomic-molecular theory) represents each individual type of atom. Modern definition of a chemical element: A chemical element is each individual type of atom, characterized by a certain positive charge on the kikos nucleus

Known chemical elements
As of November 2009, 117 chemical elements are known,

(with serial numbers from 1 to 116 and 118), of which 94 were found in nature (some only in trace quantities), the remaining 23 were obtained artificially as a result nuclear reactions.

The first 112 elements have permanent names, the rest have temporary names.
The discovery of element 112 (the heaviest of the official ones) is recognized by the International Union for Pure and Applied Chemistry. The most stable known isotope of this element has a half-life of 34 seconds. At the beginning of June 2009, it bears the unofficial name of ununbium, and was first synthesized in February 1996 at the heavy ion accelerator at the Heavy Ion Institute (Gesellschaft für Schwerionenforschung, GSI) in Darmstadt, Germany (as a result of bombarding a lead target with zinc nuclei). Discoverers have six months to propose a new official name to add to the table (they have already proposed Wickhausius, Helmholtzius, Venusius, Frischius, Strassmannius and Heisenbergius). Currently, transuranic elements with numbers 113-116 and 118 are known, obtained at the Joint Institute for Nuclear Research in Dubna, but they have not yet been officially recognized.

Chemical element symbols

The element symbol represents
- Item name
- One atom of an element
- One mole of atoms of this element

Chemical element symbols are used as abbreviations for the names of elements. The initial letter of the element name is usually taken as a symbol and, if necessary, the next one or one of the following is added. Usually these are the initial letters of the Latin names of the elements: Cu - copper (cuprum), Ag - silver (argentum), Fe - iron (ferrum), Au - gold (aurum), Hg - mercury (hydrargirum).

The number in front of the element symbol can be used to indicate the number of atoms or moles of atoms of that element. Examples:

- 5H - five atoms of the element hydrogen, five moles of atoms of the element hydrogen
- 3S - three atoms of the element sulfur, three moles of sulfur atoms

Smaller numbers next to the element symbol indicate: top left - atomic mass, bottom left - atomic number, top right - ion charge, bottom right - number of atoms in the molecule

Examples:
- H2 is a hydrogen molecule consisting of two hydrogen atoms
- Cu2+ - copper ion with charge 2+
- ()^(12)_6C - a carbon atom with a nuclear charge of 6 and an atomic mass of 12.

Story
System chemical symbols was proposed in 1811. Swedish chemist J. Berzelius. The temporary symbols for elements consist of three letters representing the abbreviation of their atomic number in Latin. The symbolism of chemical elements reveals not only high-quality composition chemical compounds, but also quantitative, since behind the symbol of each element lies the charge of the atomic nucleus inherent only to it, which determines the number of electrons in the atomic shell of a neutral atom and, thus, its chemical properties. Atomic mass was also considered earlier (in the 19th - early 20th century) characteristic property, which quantifies a chemical element, however, with the discovery of isotopes, it became clear that different sets of atoms of the same element can have different atomic masses; Thus, radiogenic helium isolated from uranium minerals, due to the predominance of the 4He isotope, has an atomic mass greater than cosmic ray helium.

Chemical element:

1 - designation of a chemical element.
2 - Russian name.
3 is the atomic number of a chemical element, equal to the number of protons in an atom.
4 - atomic mass.
5 - distribution of electrons by energy levels.
6 - electronic configuration.

Prevalence of chemical elements in nature:
Of all the chemical elements found in nature, 88; elements such as technetium Tc (serial number 43), promethium Pm (61), astatine At (85) and francium Fr (87), as well as all the elements following uranium U (serial number 92), were obtained artificially for the first time. Some of them are found in nature in vanishingly small quantities.

The most common chemical elements in earth's crust oxygen and silicon. These elements, together with the elements aluminum, iron, calcium, sodium, potassium, magnesium, hydrogen and titanium, make up more than 99% of the mass of the earth's shell, so that the remaining elements account for less than 1%. In sea water, in addition to oxygen and hydrogen - components of the water itself, elements such as chlorine, sodium, magnesium, sulfur, potassium, bromine and carbon have a high content. The mass content of an element in the earth's crust is called the clarke number or clarke of the element.

The content of elements in the Earth's crust differs from the content of elements in the Earth taken as a whole, since the chemical compositions of the Earth's crust, mantle and core are different. Thus, the core consists mainly of iron and nickel. In turn, the abundances of elements in the Solar System and in the Universe as a whole also differ from those on Earth. The most abundant element in the Universe is hydrogen, followed by helium. The study of the relative abundances of chemical elements and their isotopes in space is an important source of information about the processes of nucleosynthesis and evolution solar system and celestial bodies.

Chemicals
A chemical substance can consist of either one chemical element (simple substance) or different ones (complex substance or chemical compound). The ability of one element to exist in the form of different simple substances, differing in properties, is called allotropy.

Physical state
Under normal conditions, the corresponding simple substances for 11 elements are gases (H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn), for 2 - liquids (Br, Hg), for the remaining elements - solids bodies. Chemical elements form about 500 simple substances.

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Chemical elements in living organisms

All living things are made up of chemical elements. It is necessary to know which elements are important for the health of plants, animals and humans, and which are harmful and in what quantities. Introduction

Let's start with those chemical elements without which life on Earth would be impossible. Hydrogen, oxygen, and their compound - water. Basics

Is a structural unit organic compounds, participating in the construction of organisms and ensuring their vital functions. Hydrogen (Hydrogenium)

Hydrogen was discovered by the Englishman H. Cavendish in 1766. It got its name from the Greek. The words khidor - water and genes - genus. Hydrogen (Hydrogenium) H. Cavendish

Oxygen is a bioelement. It is only 21% in the atmosphere. Living organisms contain about 70% oxygen. Oxygen (Oxygenium)

Oxygen is necessary for the respiration of all living organisms; it is the main participant in redox reactions. It also participates in the construction of organisms and ensuring their vital functions. Oxygen (Oxygenium)

Participates in the processes of photosynthesis and respiration. All oxygen arose due to the activity of green plants, which release oxygen during photosynthesis in the light. Oxygen in plant life Photosynthesis

Most living organisms use oxygen for respiration and are therefore aerobic organisms. But everyone needs a different amount of oxygen. For example, different breeds of fish require different amounts of oxygen in the water. For some it’s 4 mg/ml, for others it’s much more. Oxygen in animal life

Oxygen accounts for 62% of the human body weight. Oxygen is found in proteins nucleic acids etc. Food oxidation is a source of energy. Oxygen is delivered by hemoglobin, which forms a compound - oxyhemoglobin. It oxidizes proteins, fats and carbohydrates, forming carbon dioxide and water, and releasing the energy necessary for life. Oxygen in human life Hemoglobin

An allotropic modification of oxygen is ozone. This is a gas formed from oxygen molecules during a thunderstorm. At an altitude of 15-20 km. Above the Earth, ozone forms a layer that protects against ultraviolet rays. I use ozone for disinfection and disinfection. Ozone Earth and the ozone layer

The main compound of hydrogen and oxygen is water. Plants are 70-80% water. The set of processes of absorption, assimilation and release of water is called the water regime. Water (Aqua) Water molecule

Water performs many functions: it is a medium for biochemical reactions, participates in photosynthesis, determines the functional activity of enzymes and structural proteins of cell membranes and organelles. Water (Aqua) in plant life

In the process of evolution, plants acquired various adaptations related to the regulation water regime in specific living conditions. Based on these characteristics, they are classified into different ecological groups. Water (Aqua) in plant life

The life activity of many bacteria takes place in a humid environment. Hydrogen bacteria are widespread in the soil, which, through the process of chemosynthesis, oxidize hydrogen, which is constantly formed during the anaerobic decomposition of various organic residues by soil microorganisms. Water (Aqua) in the life of bacteria 2 H 2 + O 2 = 2H 2 O+ energy

Water with minerals dissolved in it is included in water-salt metabolism - a set of processes of consumption, absorption and excretion of water and salts. Water (Aqua) in the life of animals and humans Water-salt metabolism ensures the constancy of the ionic composition, acid-base balance and volume of fluids in the internal environment of the body

In addition to ordinary water, there is metabolic water, which is formed during the metabolic process. It is necessary for normal development embryo. In camels, water is formed during the oxidation of fats. From 100 grams – 107 ml. water. Water (Aqua) in the life of animals and humans Camels in the desert. The humps contain metabolic water.

The role of water in the life of living organisms is enormous. If a person loses 50% of his weight as a result of starvation, he may remain alive, but if he loses 15-20% of his weight as a result of dehydration, he will die. Water (Aqua) in the life of animals and humans

The next group of chemical elements is also very important for life. A person should consume at least 400 mg of them per day. And substances such as Na and K – 3000 mg per day. Ca, P, Na, K, Mg

Calcium was discovered by H. Davy in 1808. The name comes from Lat. kalcis (stone, limestone). The daily intake of calcium in the body is 800-1500 mg. Calcium H. Davy

In the animal's body, calcium is 1.9-2.5%. Calcium is a material for the construction of bone skeletons. Calcium carbonate CaCO 3 is part of corals, shells, shells and skeletons of microorganisms. The role of calcium in animal life

In the human body, 98-99% of calcium is found in bones. Calcium is necessary for the processes of hematopoiesis and blood coagulation, for the regulation of heart function, metabolism, and for normal bone growth (skeleton, teeth). The role of calcium in human life

Calcium is found in fermented milk products, vegetables, fruits, almonds, cereals... But the most calcium is found in cheeses. Where is calcium found?

CaCo 3 - calcite, chalk, etc. Ca 3 (PO 4) 2 - bone meal Ca (NO 3) 2 - calcium. nitrate CaO – quicklime Ca(OH) 2 - lime water CaOCl 2 – bleach Calcium compounds Calcite

Phosphorus is part of the most important cell substances: DNA, RNA, phospholipids, glycerol and ATP. Phosphorus was discovered by H. Brand in 1669. Phosphorus (P) Brand discovers phosphorus. Painting by J. Wright

Phosphorus makes up 0.1-0.7% of the plant weight. Phosphorus accelerates the ripening of fruits, so phosphorus fertilizers are actively used in agriculture. Phosphorus in plant life

With a lack of phosphorus, metabolism slows down, roots weaken, leaves turn purple... Phosphorus in plant life

The human body contains 4.5 kg of phosphorus. Phosphorus is part of lipids, DNA, RNA, ATP. Almost all the most important human processes are associated with the transformation of phosphorus-containing substances. Phosphorus in human life DNA molecule

The body needs twice as much phosphorus as calcium. But calcium and phosphorus cannot live without each other. Phosphorus, like calcium, is an integral part of bone tissue. If the balance of phosphorus and calcium is disturbed, the body will have to take reserves from bones and teeth to survive. Phosphorus in human life The daily intake of phosphorus is 1000-1300 mg.

In actively working organs - liver, muscles, brain - ATP is consumed most intensively. ATP is energy, and phosphorus plays one of the main roles in this nucleotide. Therefore A.E. Fersman called phosphorus “the element of life and thought.” Phosphorus in human life ATP molecule

White phosphorus oxidizes in air, giving a green glow. Very poisonous. Used in the production of sulfuric acid and red phosphorus. White phosphorus

Powder, non-toxic, non-flammable. Used as a filler in incandescent lamps and in the production of matches. Red phosphorus

Sodium is important for the transport of substances through cell membranes. Sodium also regulates carbon transport in the plant. With its deficiency, inhibition occurs in the formation of chlorophyll. Sodium in plant life

Sodium is distributed throughout the body. 40% of sodium is found in bone tissue, some in red blood cells, muscles, etc. Sodium in human life The daily intake of sodium is 4000-6000 mg.

Sodium is part of the sodium-potassium pump, a special protein that pumps sodium ions out of the cell and pumps in potassium ions, thereby ensuring the active transport of things into the cell. Sodium in human life

Sodium maintains acid-base balance in the body, regulates blood pressure, protein synthesis and much more. Lack of sodium leads to headaches, weakness, and loss of appetite. Sodium in human life Table salt is one of the main sources of sodium.

The role of potassium in plant life is great. Potassium is found in fruits, stems, roots, and leaves. It activates synthesis organic matter, regulates carbon transport, affects nitrogen metabolism and water balance. Potassium in plant life

If there is a lack of potassium, excess ammonia accumulates in the cells, which can lead to the death of the plant. A sign of element deficiency is yellow leaves. Potassium in plant life

Potassium is part of the sodium-potassium pump. The human body weighing 70 kg contains 140 grams of potassium. An adult should consume 2-3 mg per 1 kg of weight per day, and a child should consume 12-13 mg per 1 kg of weight. A lack of potassium leads to eye disease, poor memory, and periodontal disease. Potassium in human life

KOH – caustic potassium KCl - sylvite K2SO4 - arcanite KAL(SO4)2*12H2O – - potassium alum Basic potassium compounds

Magnesium is involved in the accumulation of solar energy; it is part of the chlorophyll molecule, being the central atom in the molecule. Magnesium in plant life

With magnesium deficiency, productivity decreases and the formation of chloroplasts is disrupted. The leaves become “marbled”: they turn pale between the veins, but remain green along the veins. Magnesium in plant life

For a person weighing 70 kg, it contains 20 grams of magnesium. It has an antiseptic effect, reduces blood pressure and cholesterol, strengthens immune system. With a lack of magnesium, the susceptibility to heart attacks increases. Magnesium in human life

We looked at several chemical elements and saw that they are all important for the life of plants, animals and humans. Many important elements were not covered in this presentation because... Only those substances that a person needs to consume in sufficiently large quantities every day were taken (minimum 300 mg). Bottom line

A student of grade 9 “A”, GOU secondary school No. 425 Zalesov A.K. worked on the presentation. Resources used: a) I.A. Shaposhnikova, I.V. Bolgova. “Periodic table in living organisms” b) www.wikipedia.org c) www.xumuk.ru

Each chemical element is a collection of atoms with the same charge of atomic nuclei and the same number of electrons in the atomic shell. The nucleus of an atom consists of protons, the number of which is equal to the atomic number of the element, and neutrons, the number of which can vary. Varieties of atoms of the same chemical element, having different mass numbers (equal to the sum of the masses of protons and neutrons forming the nucleus), are called isotopes. In nature, many chemical elements are represented by two or more isotopes. There are 276 known stable isotopes belonging to 81 natural chemical elements, and about 2000 radioactive isotopes. The isotopic composition of natural elements on Earth is usually constant; therefore, each element has an almost constant atomic mass, which is one of the most important characteristics element. More than 110 chemical elements are known; they, mostly non-radioactive, create a wide variety of simple and complex substances. A simple substance is a form of existence of an element in a free form. Some chemical elements exist in two or more allotropic modifications(for example, carbon in the form of graphite and diamond), differing in physical and chemical properties; the number of simple substances reaches 400. Sometimes the concepts of “element” and “simple substance” are identified, since in the overwhelming majority of cases there is no difference in the names of chemical elements and the simple substances they form; “...nevertheless, such a difference in concepts must always exist,” wrote D. I. Mendeleev in 1869. Taylor G. Basics organic chemistry for students of non-chemical specialties. - M.: 1989. A complex substance - a chemical compound - consists of chemically bonded atoms of two or more various elements; More than 100 thousand inorganic and millions of organic compounds are known. To designate chemical elements they are used chemical signs, consisting of the first or the first and one of the subsequent letters of the Latin name of the element (With one exception, the second letter of the chemical Element Curium, named after Marie Skladowska-Curie, "m" means Maria). IN chemical formulas And chemical equations each such sign (symbol) expresses, in addition to the name of the element, the relative mass of the chemical element, equal to its atomic mass. The study of chemical elements is the subject of chemistry, in particular inorganic chemistry. Artemenko A.I. Organic chemistry. - M., 2007

Historical information. In the pre-scientific period of chemistry, the teaching of Empedocles that the basis of all things is made up of four elements was accepted as something immutable: fire, air, water, earth. This teaching, developed by Aristotle, was fully accepted by the alchemists. In the 8th-9th centuries, they supplemented it with the idea of ​​sulfur (the beginning of flammability) and mercury (the beginning of metallicity) as components of all metals. In the 16th century, the idea of ​​salt as the beginning of non-volatility and fire constancy arose. The doctrine of 4 elements and 3 principles was opposed by R. Boyle, who in 1661 gave the first scientific definition chemical elements as simple substances that do not consist of any other substances or of each other and form all mixed (complex) bodies. In the 18th century, the hypothesis of I. I. Becher and G. E. Stahl, according to which the bodies of nature consist of water, earth and the principle of flammability - phlogiston, received almost universal recognition. At the end of the 18th century, this hypothesis was refuted by the works of A. L. Lavoisier. He defined chemical elements as substances that could not be decomposed into simpler ones and from which other (complex) substances are composed, that is, he essentially repeated Boyle’s formulation. But, unlike him, Lavoisier gave the first list of real chemical elements in the history of science. It included all non-metals known then (1789) (O, N, H, S, P, C), metals (Ag, As, Bi, Co, Ca, Sn, Fe, Mn, Hg, Mo, Ni, Au, Pt, Pb, W, Zn), as well as “radicals” [murium (Cl), fluoride (F) and boron (B)] and “earths” - not yet decomposed lime CaO, magnesia MgO, barite BaO, alumina Al2O2 and silica SiO2 (Lavoisier believed that “earths” were complex substances, but until this was proven experimentally, he considered them chemical elements). As a tribute to the times, he included weightless “fluids” - light and caloric - in the list of chemical elements. He considered the caustic alkalis NaOH and KOH to be complex substances, although it was possible to decompose them by electrolysis later - only in 1807 (G. Davy). J. Dalton's development of atomic theory had one of the consequences of clarifying the concept of an element as a type of atom with the same relative mass (atomic weight). Dalton compiled the first table in 1803 atomic masses(relative to the mass of a hydrogen atom, taken as one) of the five chemical Elements (O, N, C, S, P). Thus, Dalton laid the foundation for the recognition of atomic mass as main characteristics element. Dalton, following Lavoisier, considered chemical elements to be substances that cannot be decomposed into simpler ones Artemenko A.I. Organic chemistry. - M., 2007.

Subsequent rapid development chemistry led, in particular, to the discovery large number chemical elements. Lavoisier's list contained only 25 chemical elements, including "radicals", but not counting "fluids" and "earths". By the time of the discovery of Mendeleev's periodic law (1869), 63 elements were already known. The discovery of D.I. Mendeleev made it possible to foresee the existence and properties of a number of then unknown chemical elements and was the basis for establishing their relationship and classification. The discovery of radioactivity in the late 19th century shook more than a century of belief that atoms could not be broken down. In this regard, the discussion about what chemical elements are continued almost until the middle of the 20th century. Put an end to it modern theory structure of the atom, which made it possible to give a strictly objective definition of chemical elements given at the beginning of the article.

Prevalence in nature. The prevalence of chemical elements in space is determined by nucleogenesis inside stars. The formation of nuclei of chemical elements is associated with various nuclear processes in the stars. Therefore, at different stages of their evolution, different stars and stellar systems have unequal chemical composition. The prevalence and distribution of chemical elements in the Universe, the processes of combination and migration of atoms during the formation of cosmic matter, chemical composition cosmic bodies studies cosmochemistry. The bulk of cosmic matter consists of H and He (99.9%). The most developed part of cosmochemistry is geochemistry Akhmetov N.S. General and inorganic chemistry. - M., 2003.

Of the 111 chemical elements, only 89 are found in nature, the rest, namely technetium (atomic number Z = 43), promethium (Z = 61), astatine (Z = 85), francium (Z = 87) and transuranium elements, are obtained artificially through nuclear reactions (tiny amounts of Tc, Pm, Np, Fr are formed during the spontaneous fission of uranium and are present in uranium ores). In the accessible part of the Earth, the most common 10 elements with atomic numbers ranging from 8 to 26. In the earth's crust they are contained in the following relative quantities:

Classification and properties Akhmetov N.S. General and inorganic chemistry. - M., 2003. The most perfect natural classification of chemical elements, revealing their relationship and showing the change in their properties depending on atomic numbers, is given by D. I. Mendeleev’s periodic system of elements. According to their properties, chemical elements are divided into metals and non-metals, and the periodic system allows us to draw a boundary between them. For chemical properties The most characteristic feature of metals is the ability to donate external electrons and form cations during chemical reactions; for non-metals, the ability to gain electrons and form anions. Nonmetals are characterized by high electronegativity. There are chemical elements of the main subgroups, or non-transition elements, in which the s and p electron subshells are sequentially filled, and chemical elements of secondary subgroups, or transition elements, in which the d- and f-subshells are being completed. At room temperature, two chemical elements exist in liquid state(Hg and Br), eleven - in gaseous form (H, N, O, F, Cl, He, Ne, Ar, Kr, Xe, Rn), the rest - in the form solids, and their melting point varies over a very wide range - from about 30 °C (Cs 28.5 °C; Ga 29.8 °C) to 3000 °C and higher (Ta 2996 °C; W 3410 °C; graphite about 3800 °C) Akhmetov N.S. General and inorganic chemistry. - M., 2003.

It only takes one sheet of paper, but this sheet contains a huge amount of information. Each cell of the table contains the international symbol of an element, its name (in our tables - in Russian), its serial number, relative atomic mass (for unstable elements - mass number). As a rule, the belonging of elements to a particular family is highlighted in color, and the structure of the electronic shells of atoms is also given. Some companies produce colorful tables in which each cell contains a photograph of the corresponding simple substance, the structure of the most stable crystal lattice is given, and information about the use of this element is given. The design of cells with radioactive elements is interesting. Thus, in one table, in place of radium, there is a photograph of Marie Curie’s work journal, open on the page where the entry about the discovery of a new element first appeared.

The original series of fifteen color postcards was released by the Association of French Chemists. It contains photographs of postage stamps issued in many countries around the world. Each stamp is dedicated to a different chemical element. And, of course, a portrait of the creator of the periodic system of elements, D.I. Mendeleev, and a photograph of the first handwritten sketch of his table take pride of place. On the stamps are portraits of scientists who discovered the elements, the minerals from which these elements are extracted, their crystal lattices, structural formulas compounds... And when the owner of this philatelic collection, professor of chemistry from the University of Dijon Jean Tirouflé, could not find a suitable stamp, he wittily got out of the situation by resorting to allegory. Thus, in place of the gallium there is a French stamp with a singing cockerel. And this is not without reason. The element gallium was predicted by Mendeleev (as eka-aluminum) and discovered in 1875 by the French chemist P.E. Lecoq de Boisbaudran, who named it after his homeland (Gallia is the Latin name for France). The symbol of France is the rooster (in French - le coq), so in the name of the element its discoverer implicitly immortalized his surname!

Mendeleev also said that the table of elements is the fruit not only of his own work, but also of the efforts of many chemists, among whom he especially noted the “strengtheners of the periodic law” who discovered the elements he predicted. Creating a modern table required many years of hard work by thousands and thousands of chemists and physicists. If Mendeleev were alive today, he, looking at the modern table of elements, could well repeat the words of the English chemist J. W. Mellor, author of the classic 16-volume encyclopedia on inorganic and theoretical chemistry. Having finished his work in 1937, after 15 years of work, he wrote with gratitude to title page: “Dedicated to the privates of a huge army of chemists. Their names are forgotten, their works remain...

Nowadays, few people know the names of those who proposed the modern scale of atomic masses, who first divided the mythical element “didymium” into praseodymium and neodymium, synthesized technetium and found traces of it in the earth’s crust - in short, everyone who made at least a small contribution to table of elements. But the table is in front of us, and the amount of information it contains is enormous. Its beginning goes back centuries, to ancient times, when the Greek philosopher Leucippus and his famous student Democritus formulated the first ideas about atoms.

Latin word element ( elementum) was used by ancient authors (Cicero, Ovid, Horace), and in many ways in the same sense as its modern meaning - as part of something (an element of speech, an element of education, etc.). The origin of the name of this word is interesting. In ancient times there was a popular saying: “Just as words are made up of letters, so bodies are made up of elements.” Hence the probable origin of this word: by the name of a number of consonant letters in the Latin alphabet: l, m, n, t (“el” – “em” – “en” – “tum”).

The Romans had a similar word in meaning principium in the meaning of “component”, “beginning”. The ancient Roman philosopher Titus Lucretius Carus in his poem About the nature of things often used the term principium(translated as “the beginning”). In this sense, it is very close to the modern “chemical” concept of an element:

As for the first principles, they have even more
Means for various things to arise from them,
There are none of the things available to our gaze,
So that it consists of completely homogeneous principles...
The origins of things are carried away by their own weight
Or the pushes of others...

(About the nature of things. Titus Lucretius Carus)

The doctrine that all substances are composed of tiny particles is called the atomic theory. The guesses of the ancients, based only on reflection, are not so far, in principle, from modern ideas: There are a limited number of different types of atoms (i.e. elements) that can combine with each other in different ways, yielding a huge variety of substances with different properties. And the process of restructuring the relative arrangement of atoms is the essence chemical reaction. The concept of atoms and elements is the greatest achievement of the human mind. The laureate spoke about this very figuratively Nobel Prize in physics Richard Feynman: “If, as a result of some global catastrophe, all the accumulated scientific knowledge would be destroyed and only one phrase would be passed down to future generations of living beings, what statement, composed of the fewest words, would bring the most information? I believe that this is - atomic hypothesis(you can call it not a hypothesis, but a fact, but this does not change anything): All bodies consist of atoms - small bodies that are in continuous motion, attracted at a short distance, but repelled if one of them is pressed more closely to the other. This one phrase... contains incredible amount of information about the world, you just need to apply a little imagination and a little consideration to it.”

Atoms of the same kind make up a chemical element. Back in the 17th century. Robert Boyle, and in the next century M.V. Lomonosov and A.L. Lavoisier clearly formulated the concept of “element” as a simple substance that cannot be decomposed into its component parts by chemical methods. The modern definition of a chemical element is very laconic: an element is a collection of atoms with a certain nuclear charge Z. Core charge equal to the number protons in it; It is precisely this that determines the essence of a chemical element, its individuality and difference from all other elements. Therefore, it should be recognized that both a colorless light gas consisting of H 2 molecules and positively charged H + cations in aqueous solutions acids, and H anions in molten lithium hydride LiH, and protons in physical accelerators or in the depths of the Sun, and “cold” neutral H atoms in interstellar spaces- all this is the element hydrogen ( Z= 1). Moreover, heavy varieties hydrogen– deuterium (D) and tritium (T), containing, in addition to one proton, one or two neutrons, as well as artificially obtained superheavy atoms 4 H and 5 H, also belong to the element hydrogen.

In total, 90 different elements have been found in nature, and more than 20 have been obtained artificially. In nature, chemical elements are found in simple and complex substances. Simple substances are formed by atoms of the same chemical element, while complex substances contain atoms of two or more elements.

The American chemist Alexander Smith, the author of one of the the best textbooks inorganic chemistry of the early 20th century: “It will be correct if we talk about the element iron and the element sulfur in iron sulfide; but a chemist will never say that this compound contains simple substances: iron and sulfur. If he had said this, we would have understood him to mean that this material is not a compound, but a mixture; we would expect some parts of this material to be magnetic, like iron, and other parts to be yellow and dissolved in carbon disulfide - which is not the case."

But simple substances, it turns out, are not so “simple”: most elements can form several simple bodies. According to the definition given in the Chemical Encyclopedia, a simple substance is a form of existence of a chemical element that differs in the number of atoms in the molecules (for example, oxygen O 2 and ozone O 3), the type of crystal lattice (for example, modifications of carbon - graphite, diamond, carbine) or other properties. So hydrogen gas at room temperature contains two simple substances - two varieties of hydrogen (orthohydrogen and parahydrogen); they are different relative position nuclear spins ( cm. MOMENTS OF ATOMS AND NUCLEI) and hydrogen can be divided into two simple substances that differ in their physical properties (for example, heat capacities). And even gases such as H 2, D 2, T 2, HD, HT, DT should be considered different simple substances, since each gas contains atoms of only one element - hydrogen, and their properties are very different. Several simple substances form O 2 molecules: two types of oxygen gas (they are called singlet and triplet, they differ electronic structure And reactivity), and at least four (!) varieties of solid oxygen (in general, the presence of several crystalline modifications for one element is the rule rather than the exception). And then there is ozone... Not surprisingly, the number of known simple substances is many times greater than the number of known elements.

In Russian, the same terms are usually used to denote both elements and simple substances. This does not make it very difficult for chemists, since it is almost always clear from the context what the we're talking about. Thus, when saying “copper coin”, “smelting copper from ores”, “high electrical conductivity of copper”, they always mean metallic copper - a simple substance. When speaking about the small distribution of copper in nature, they do not mean a metal at all (native copper is an extremely rare mineral), but the element copper, the atoms of which can be included in various minerals. Stating that “copper occupies a place in the periodic table between nickel and zinc,” the chemist also means not pieces of metal in the cells of the table, but the element copper as a collection of its atoms with a nuclear charge Z = 29.

Different terms for an element and the simple substances it forms are rare. In addition to deuterium and tritium, carbon should be mentioned. Carbon is the “giving birth coal,” but it is not coal itself, but a chemical element. Carbon is found in ocean water and the atmosphere, in the body of humans and animals, and in many minerals. The pencil core and the decoration on the ring are made of simple substances - graphite and diamond. Other simple substances formed by the element carbon are now known - lonsdaleite, carbyne, various fullerenes, nanotubes (fullerenes and nanotubes are often combined under the same name “fullerite”).

The concept of a simple substance, like many other basic concepts of chemistry, is partly arbitrary. After all, an “iron” nail is not made of iron at all, but of low-carbon steel containing a small amount of carbon. A gold coin contains at least 10% copper or silver (pure gold is very soft). And even the purest semiconductor silicon contains minute amounts of atoms of other elements. The number of relatively pure simple substances around us in everyday life is small: these are aluminum and copper in wires, tungsten, molybdenum, krypton in light bulbs, hydrogen and helium in balloons, silver, gold, platinum, palladium in high-grade jewelry and coins, mercury in a thermometer, tin in a tin can, chromium and nickel in metal products, sulfur for pest control, zinc in electric batteries...

The atoms (or rather, nuclei) of any chemical element are built from a whole number of the simplest “building blocks” - the nuclei of hydrogen atoms (protons) and uncharged neutrons. The number of protons determines which specific element a given nucleus belongs to. But the number of protons in the nuclei of atoms of a given element can be different (the sum of protons and neutrons in the nucleus is called the mass number). Varieties of atoms of a given element, differing in the number of neutrons in the nucleus and, therefore, in mass, are called isotopes. This term was proposed in 1910 by the English chemist Frederick Soddy, who derived it from Greek words isos – equal, identical and topos – place, i.e. occupying the same cell in the periodic table. Different isotopes of a given element are named in the same way as the element itself with the addition of a mass number: chlorine-35, chlorine-37. Isotopes are designated by the symbols of the corresponding element with the mass number indicated at the top left: 35 Cl, 37 Cl, etc. A specific nucleus (or atom) with a certain mass number is called a nuclide (from the Latin nucleus - nucleus). Therefore, the following statement will be correct: natural chlorine is represented by two isotopes, oxygen by three (nuclides 16 O, 17 O and 18 O), sulfur by four, titanium by five, calcium by six, molybdenum by seven, cadmium by eight, xenon by nine , and the record belongs to tin - it has ten isotopes (nuclides from 112 Sn to 124 Sn with the exception of 113 Sn, 121 Sn and 123 Sn. Some elements in nature are represented by only one nuclide - these are 9 Be, 19 F, 23 Na, 27 Al , 31 P, 45 Sc, 59 Co, 75 As, 89 Y, 93 Nb, 103 Rh, 127 I, 133 Cs, 141 Pr, 159 Tb, 165 Ho, 169 Tm, 197 Au, 209 Bi (only stable, that is, non-radioactive nuclides). It is noteworthy that all the so-called “single elements” are represented by nuclides with an odd mass number.

In Soddy's time, isotopes were the names given to the different radioactive varieties of atoms of a given element. At the same time, the identity of a particular nuclide to a given element was often unknown, and many of them had their own names, for example, RaA (nuclide 218 Po), RaB (214 Pb), RaC (214 Bi), RaC" (214 Po), RaC"" (210 Tl), RaD (210 Pb), RaE (210 Bi), two “mesothoriums”: MsTh 1 (nuclide 228 Ra) and MsTh 2 (nuclide 228 Ac) “radiothorium” RdTh (nuclide 228 Th), gaseous isotopes of radon – “emanations” (from Latin emanatio– outflow): emanation of radium RaEm (nuclide 222 Rn), actinium AcEm (nuclide 219 Rn) and thorium ThEm (nuclide 220 Rn), etc. Some of these names are still sometimes used in radiochemistry. Currently, different names are generally accepted only for hydrogen isotopes - protium (1 H), deuterium (2 H or D), tritium (3 H or T). This happens because hydrogen is one of the essential elements, and its different isotopes differ very greatly - several times - in mass and therefore have not only different physical properties, but also different reactivity. For example, deuterium and its compounds are generally less reactive and react more slowly than the light isotope (kinetic isotope effect). Currently, about 280 stable and more than 2000 radioactive isotopes of chemical elements are known.

Ilya Leenson