19 in the periodic table. General characteristics of chemical elements

A chemical element is a collective term that describes a collection of atoms simple substance, i.e. 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 to this, chemical compound, for example, iron oxide, always contains at least two various types 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: letter or pair Latin letters, representing the designation of this element.

Chemical compound: a substance that is made up of two or more chemical elements, connected to 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 usually a product 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 during 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

Name	Symbol	Percentage of all atoms *				Properties of chemical elements (under normal room conditions)
Name	Symbol	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	Found in natural minerals, shells, bones
Carbon	WITH	-	-	-	10,7	The basis of all living organisms
Chlorine	Cl	-	-	0,3	-	Poisonous gas
Copper	Cu	-	-	-	-	Red metal only
Gold	Au	-	-	-	-	Yellow metal only
Helium	He	7,1	-	-	-	Very light gas
Hydrogen	N	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 to produce 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	ABOUT	-	60,1	33,1	25,7	Gas, the second important one air component
Phosphorus	R	-	-	-	0,1	Non-metal; important for plants
Potassium	TO	-	1.1	-	-	Metal; important for plants; usually called "potash"

* 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 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 together 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? Whether there is a common law, uniting them?

Chemists suggested various systems 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 from the so-called halogen group (chlorine, bromine and iodine) could be classified according to 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 Dmitry 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 periodic law, because he took one step that Meyer didn't take. 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% total number options are tables, and the rest is geometric figures, mathematical curves, etc. As a result practical use found four types of tables: short, half-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 located in the same period have properties that slowly change from 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 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.

He relied on the works of Robert Boyle and Antoine Lavuzier. The first scientist advocated the search for indecomposable chemical elements. Boyle listed 15 of these back in 1668.

Lavouzier added 13 more to them, but a century later. The search dragged on because there was no coherent theory of the connection between the elements. Finally, Dmitry Mendeleev entered the “game”. He decided that there was a connection between the atomic mass of substances and their place in the system.

This theory allowed the scientist to discover dozens of elements without discovering them in practice, but in nature. This was placed on the shoulders of descendants. But now it’s not about them. Let's dedicate the article to the great Russian scientist and his table.

The history of the creation of the periodic table

Mendeleev table began with the book “Relationship of properties with the atomic weight of elements.” The work was published in the 1870s. At the same time, the Russian scientist spoke before the country’s chemical society and sent out the first version of the table to colleagues from abroad.

Before Mendeleev, 63 elements were discovered by various scientists. Our compatriot began by comparing their properties. First of all, I worked with potassium and chlorine. Then, I took up the group of metals of the alkali group.

The chemist acquired a special table and element cards to play them like solitaire, looking for the necessary matches and combinations. As a result, an insight came: - the properties of components depend on the mass of their atoms. So, elements of the periodic table lined up.

The chemistry maestro's discovery was the decision to leave empty spaces in these rows. The periodicity of the difference between atomic masses forced the scientist to assume that not all elements are known to humanity. The weight gaps between some of the “neighbors” were too large.

That's why, periodic table Mendeleev became like a chess field, with an abundance of “white” cells. Time has shown that they were indeed waiting for their “guests”. For example, they became inert gases. Helium, neon, argon, krypton, radioactivity and xenon were discovered only in the 30s of the 20th century.

Now about the myths. It is widely believed that periodic chemical table appeared to him in a dream. These are the machinations of university teachers, or rather, one of them - Alexander Inostrantsev. This is a Russian geologist who lectured at the St. Petersburg University of Mining.

Inostrantsev knew Mendeleev and visited him. One day, exhausted from the search, Dmitry fell asleep right in front of Alexander. He waited until the chemist woke up and saw Mendeleev grab a piece of paper and write down the final version of the table.

In fact, the scientist simply did not have time to do this before Morpheus captured him. However, Inostrantsev wanted to amuse his students. Based on what he saw, the geologist came up with a story, which grateful listeners quickly spread to the masses.

Features of the periodic table

Since the first version in 1969 periodic table has been modified more than once. Thus, with the discovery of noble gases in the 1930s, it was possible to derive a new dependence of elements - on their atomic numbers, and not on mass, as the author of the system stated.

The concept of “atomic weight” was replaced by “atomic number”. It was possible to study the number of protons in the nuclei of atoms. This figure is the serial number of the element.

20th century scientists studied and electronic structure atoms. It also affects the periodicity of elements and is reflected in later editions Periodic tables. Photo The list demonstrates that the substances in it are arranged as their atomic weight increases.

They did not change the fundamental principle. The mass increases from left to right. At the same time, the table is not single, but divided into 7 periods. Hence the name of the list. The period is a horizontal row. Its beginning is typical metals, its end is elements with non-metallic properties. The decrease is gradual.

There are large and small periods. The first ones are at the beginning of the table, there are 3 of them. A period of 2 elements opens the list. Next come two columns, each containing 8 items. The remaining 4 periods are large. The 6th is the longest, with 32 elements. In the 4th and 5th there are 18 of them, and in the 7th - 24.

You can count how many elements are in the table Mendeleev. There are 112 titles in total. Namely names. There are 118 cells, and there are variations of the list with 126 fields. There are still empty cells for undiscovered elements that do not have names.

Not all periods fit on one line. Large periods consist of 2 rows. The amount of metals in them outweighs. Therefore, the bottom lines are completely dedicated to them. A gradual decrease from metals to inert substances is observed in the upper rows.

Pictures of the periodic table divided and vertical. This groups in the periodic table, there are 8 of them. Elements similar in chemical properties. They are divided into main and secondary subgroups. The latter begin only from the 4th period. The main subgroups also include elements of small periods.

The essence of the periodic table

Names of elements in the periodic table– this is 112 positions. The essence of their arrangement into a single list is the systematization of the primary elements. People began to struggle with this back in ancient times.

Aristotle was one of the first to understand what all things are made of. He took as a basis the properties of substances - cold and heat. Empidocles identified 4 fundamental elements according to the elements: water, earth, fire and air.

Metals in the periodic table, like other elements, are the same fundamental principles, but from a modern point of view. The Russian chemist managed to discover most of the components of our world and suggest the existence of still unknown primary elements.

It turns out that pronunciation of the periodic table– voicing a certain model of our reality, breaking it down into its components. However, learning them is not so easy. Let's try to make the task easier by describing a couple of effective methods.

How to learn the periodic table

Let's start with modern method. Computer scientists have developed a number of flash games to help memorize Periodic List. Project participants are asked to find elements using different options, for example, name, atomic mass, or letter designation.

The player has the right to choose the field of activity - only part of the table, or all of it. It is also our choice to exclude element names and other parameters. This makes the search difficult. For the advanced, there is also a timer, that is, the training is carried out at speed.

Game conditions do study numbers of elements in the Mendleyev table not boring, but entertaining. Excitement awakens, and it becomes easier to systematize knowledge in your head. Those who do not accept computer flash projects offer more traditional way memorizing the list.

It is divided into 8 groups, or 18 (according to the 1989 edition). For ease of memorization, it is better to create several separate tables rather than work on a whole version. Visual images matched to each of the elements also help. You should rely on your own associations.

Thus, iron in the brain can be correlated, for example, with a nail, and mercury with a thermometer. Is the element name unfamiliar? We use the method of suggestive associations. , for example, let’s make up the words “toffee” and “speaker” from the beginnings.

Characteristics of the periodic table Don't study in one sitting. Exercises of 10-20 minutes a day are recommended. It is recommended to start by memorizing only the basic characteristics: the name of the element, its designation, atomic mass and serial number.

Schoolchildren prefer to hang the periodic table above their desk, or on a wall they often look at. The method is good for people with a predominance of visual memory. Data from the list is involuntarily remembered even without cramming.

Teachers also take this into account. As a rule, they do not force you to memorize the list; they allow you to look at it even during tests. Constantly looking at the table is equivalent to the effect of a printout on the wall, or writing cheat sheets before exams.

When starting to study, let us remember that Mendeleev did not immediately remember his list. Once, when a scientist was asked how he discovered the table, the answer was: “I’ve been thinking about it for maybe 20 years, but you think: I sat there and suddenly it’s ready.” The periodic system is painstaking work that cannot be completed in a short time.

Science does not tolerate haste, because it leads to misconceptions and annoying mistakes. So, at the same time as Mendeleev, Lothar Meyer also compiled the table. However, the German was a little flawed in his list and was not convincing in proving his point. Therefore, the public recognized the work of the Russian scientist, and not his fellow chemist from Germany.

Knowing the formulation of the periodic law and using D.I. Mendeleev’s periodic system of elements, one can 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 the chemical element in periodic table elements D.I. Mendeleev:

serial number;
period number;
group number;
subgroup (main or secondary).

III. Structure of an atom of a chemical element:

charge of the nucleus of an atom;
relative atomic mass chemical element;
number of protons;
number of electrons;
number of neutrons;
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 the 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, subgroup type).

Phosphorus is in the main subgroup of group V, in the 3rd period.

III. We will provide a general description of the 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 outer level of a phosphorus atom: at the third energy level, at the 3s sublevel, there are two electrons (two arrows with opposite direction), there are three electrons on three p-sublevels (in each of the three cells one arrow is written, 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 the properties of an acidic oxide. The hydroxide corresponding to the 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. The nonmetallic properties of atoms of chemical elements of the main subgroups with increasing atomic 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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