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 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.

Scientists of the 20th century also studied the electronic structure of atoms. It also affects the periodicity of elements and is reflected in later editions Periodic tables. Photo The list shows 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 with similar chemical properties are arranged vertically. 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 principles 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 the 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 make learning 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 a more traditional way of memorizing a 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 remembering 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.

2.1. Chemical language and its parts

Humanity uses many different languages. Except natural languages(Japanese, English, Russian - more than 2.5 thousand in total), there are also artificial languages, for example, Esperanto. Among artificial languages ​​there are languages various sciences. So, in chemistry they use their own, chemical language.
Chemical language– a system of symbols and concepts designed for a brief, succinct and visual recording and transmission of chemical information.
A message written in most natural languages ​​is divided into sentences, sentences into words, and words into letters. If we call sentences, words and letters parts of language, then we can identify similar parts in chemical language (Table 2).

Table 2.Parts of chemical language

It is impossible to master any language immediately; this also applies to a chemical language. Therefore, for now you will only get acquainted with the basics of this language: learn some “letters”, learn to understand the meaning of “words” and “sentences”. At the end of this chapter you will be introduced to names chemical substances are an integral part of the chemical language. As you study chemistry, your knowledge of chemical language will expand and deepen.

CHEMICAL LANGUAGE.
1.What artificial languages ​​do you know (other than those mentioned in the text of the textbook)?
2.How do natural languages ​​differ from artificial ones?
3. Do you think it is possible to describe chemical phenomena without using chemical language? If not, why not? If so, what would be the advantages and disadvantages of such a description?

2.2. Chemical element symbols

The symbol for a chemical element represents the element itself or one atom of that element.
Each such symbol is an abbreviated Latin name of a chemical element, consisting of one or two letters of the Latin alphabet (for the Latin alphabet, see Appendix 1). The symbol is written with a capital letter. Symbols, as well as Russian and Latin names of some elements, are given in Table 3. Information about the origin of the Latin names is also given there. There is no general rule for the pronunciation of symbols, therefore Table 3 also shows the “reading” of the symbol, that is, how this symbol is read in the chemical formula.

It is impossible to replace the name of an element with a symbol in oral speech, but in handwritten or printed texts this is allowed, but not recommended. Currently, 110 chemical elements are known, 109 of them have names and symbols approved by the International Union of Pure and Applied Chemistry (IUPAC).
Table 3 provides information on only 33 elements. These are the elements that you will encounter first when studying chemistry. Russian names (in alphabetical order) and symbols of all elements are given in Appendix 2.

Table 3.Names and symbols of some chemical elements

Name
	Latin		Writing
-	Writing	Origin	-	-
Nitrogen	N itrogenium	From Greek "giving birth to saltpeter"		"en"
Aluminum	Al uminium	From Lat. "alum"		"aluminum"
Argon	Ar gon	From Greek "inactive"		"argon"
Barium	Ba rium	From Greek " heavy"		"barium"
Bor	B orum	From Arabic "white mineral"		"boron"
Bromine	Br omum	From Greek "smelly"		"bromine"
Hydrogen	H hydrogenium	From Greek "giving birth to water"		"ash"
Helium	He lium	From Greek " Sun"		"helium"
Iron	Fe rrum	From Lat. "sword"		"ferrum"
Gold	Au rum	From Lat. "burning"		"aurum"
Iodine	I odum	From Greek " violet"		" iodine"
Potassium	K alium	From Arabic "lye"		"potassium"
Calcium	Ca lcium	From Lat. "limestone"		"calcium"
Oxygen	O xygenium	From Greek "acid-generating"		" O"
Silicon	Si licium	From Lat. "flint"		"silicium"
Krypton	Kr ypton	From Greek "hidden"		"krypton"
Magnesium	M a g nesium	From the name Magnesia Peninsula		"magnesium"
Manganese	M a n ganum	From Greek "cleansing"		"manganese"
Copper	Cu prum	From Greek name O. Cyprus		"cuprum"
Sodium	Na trium	From Arabic, "detergent"		"sodium"
Neon	Ne on	From Greek " new"		"neon"
Nickel	Ni ccolum	From him. "St. Nicholas Copper"		"nickel"
Mercury	H ydrar g yrum	Lat. "liquid silver"		"hydrargyrum"
Lead	P lum b um	From Lat. names of an alloy of lead and tin.		"plumbum"
Sulfur	S ulfur	From Sanskrit "combustible powder"		"es"
Silver	A r g entum	From Greek " light"		"argentum"
Carbon	C arboneum	From Lat. " coal"		"tse"
Phosphorus	P hosphorus	From Greek "bringer of light"		"peh"
Fluorine	F luorum	From Lat. verb "to flow"		"fluorine"
Chlorine	Cl orum	From Greek "greenish"		"chlorine"
Chromium	C h r omium	From Greek " dye"		"chrome"
Cesium	C ae s ium	From Lat. "sky blue"		"cesium"
Zinc	Z i n cum	From him. "tin"		"zinc"

2.3. Chemical formulas

Used to designate chemical substances chemical formulas.

For molecular substances, a chemical formula can denote one molecule of this substance.
Information about a substance may vary, so there are different types of chemical formulas.
Depending on the completeness of the information, chemical formulas are divided into four main types: protozoa, molecular, structural And spatial.

Subscripts in the simplest formula do not have a common divisor.
The index "1" is not used in formulas.
Examples of the simplest formulas: water - H 2 O, oxygen - O, sulfur - S, phosphorus oxide - P 2 O 5, butane - C 2 H 5, phosphoric acid - H 3 PO 4, sodium chloride (table salt) - NaCl.
The simplest formula of water (H 2 O) shows that the composition of water includes the element hydrogen(H) and element oxygen(O), and in any portion (a portion is a part of something that can be divided without losing its properties.) of water, the number of hydrogen atoms is twice the number of oxygen atoms.
Number of particles, including number of atoms, denoted by a Latin letter N. Denoting the number of hydrogen atoms – N H, and the number of oxygen atoms is N O, we can write that

Or N H: N O=2:1.

The simplest formula of phosphoric acid (H 3 PO 4) shows that phosphoric acid contains atoms hydrogen, atoms phosphorus and atoms oxygen, and the ratio of the numbers of atoms of these elements in any portion of phosphoric acid is 3:1:4, that is

NH: N P: N O=3:1:4.

The simplest formula can be compiled for any individual chemical substance, and for a molecular substance, in addition, it can be compiled molecular formula.

Examples of molecular formulas: water - H 2 O, oxygen - O 2, sulfur - S 8, phosphorus oxide - P 4 O 10, butane - C 4 H 10, phosphoric acid - H 3 PO 4.

Non-molecular substances do not have molecular formulas.

The sequence of writing element symbols in simple and molecular formulas is determined by the rules of chemical language, which you will become familiar with as you study chemistry. The information conveyed by these formulas is not affected by the sequence of symbols.

Of the signs reflecting the structure of substances, we will only use for now valence stroke("dash"). This sign shows the presence between the atoms of the so-called covalent bond(what type of connection this is and what its features are, you will soon find out).

In a water molecule, an oxygen atom is connected by simple (single) bonds to two hydrogen atoms, but the hydrogen atoms are not connected to each other. This is precisely what the structural formula of water clearly shows.

Another example: the sulfur molecule S8. In this molecule, 8 sulfur atoms form an eight-membered ring, in which each sulfur atom is connected to two other atoms by simple bonds. Compare the structural formula of sulfur with the three-dimensional model of its molecule shown in Fig. 3. Please note that the structural formula of sulfur does not convey the shape of its molecule, but only shows the sequence of connection of atoms by covalent bonds.

The structural formula of phosphoric acid shows that in the molecule of this substance one of the four oxygen atoms is connected only to the phosphorus atom by a double bond, and the phosphorus atom, in turn, is connected to three more oxygen atoms by single bonds. Each of these three oxygen atoms is also connected by a simple bond to one of the three hydrogen atoms present in the molecule.

Compare the following three-dimensional model of a methane molecule with its spatial, structural and molecular formula:

In the spatial formula of methane, wedge-shaped valence strokes, as if in perspective, show which of the hydrogen atoms is “closer to us” and which is “further from us”.

Sometimes the spatial formula indicates bond lengths and angles between bonds in a molecule, as is shown in the example of a water molecule.

Non-molecular substances do not contain molecules. For the convenience of chemical calculations in a non-molecular substance, the so-called formula unit.

Examples of the composition of formula units of some substances: 1) silicon dioxide (quartz sand, quartz) SiO 2 – a formula unit consists of one silicon atom and two oxygen atoms; 2) sodium chloride (table salt) NaCl – the formula unit consists of one sodium atom and one chlorine atom; 3) iron Fe - a formula unit consists of one iron atom. Like a molecule, a formula unit is the smallest portion of a substance that retains its chemical properties.

Table 4

Information conveyed by different types of formulas

Formula type	Information conveyed by the formula.
The simplest Molecular Structural Spatial		The atoms of which elements make up the substance. Relationships between the numbers of atoms of these elements. The number of atoms of each element in a molecule. Types of chemical bonds. The sequence of joining atoms by covalent bonds. Multiplicity of covalent bonds. Mutual arrangement of atoms in space. Bond lengths and angles between bonds (if specified).

Let us now consider, using examples, what information different types of formulas give us.

1. Substance: acetic acid. The simplest formula is CH 2 O, molecular formula is C 2 H 4 O 2, structural formula

The simplest formula tells us that
1) acetic acid contains carbon, hydrogen and oxygen;
2) in this substance the number of carbon atoms relates to the number of hydrogen atoms and the number of oxygen atoms, as 1: 2: 1, that is N H: N C: N O = 1:2:1.
Molecular formula adds that
3) in a molecule of acetic acid there are 2 carbon atoms, 4 hydrogen atoms and 2 oxygen atoms.
Structural formula adds that
4, 5) in a molecule two carbon atoms are connected to each other by a simple bond; one of them, in addition, is connected to three hydrogen atoms, each with a single bond, and the other to two oxygen atoms, one with a double bond and the other with a single bond; the last oxygen atom is still connected by a simple bond to the fourth hydrogen atom.

2. Substance: sodium chloride. The simplest formula is NaCl.
1) Sodium chloride contains sodium and chlorine.
2) In this substance, the number of sodium atoms is equal to the number of chlorine atoms.

3. Substance: iron. The simplest formula is Fe.
1) This substance contains only iron, that is, it is a simple substance.

4. Substance: trimetaphosphoric acid . The simplest formula is HPO 3, molecular formula is H 3 P 3 O 9, structural formula

1) Trimetaphosphoric acid contains hydrogen, phosphorus and oxygen.
2) N H: N P: N O = 1:1:3.
3) The molecule consists of three hydrogen atoms, three phosphorus atoms and nine oxygen atoms.
4, 5) Three phosphorus atoms and three oxygen atoms, alternating, form a six-membered cycle. All connections in the cycle are simple. Each phosphorus atom is, in addition, connected to two more oxygen atoms, one with a double bond and the other with a single bond. Each of the three oxygen atoms connected by simple bonds to phosphorus atoms is also connected by a simple bond to a hydrogen atom.

Phosphoric acid – H 3 PO 4(another name is orthophosphoric acid) is a transparent, colorless, crystalline substance of molecular structure that melts at 42 o C. This substance dissolves very well in water and even absorbs water vapor from the air (hygroscopic). Phosphoric acid is produced in large quantities and is used primarily in the production of phosphate fertilizers, but also in the chemical industry, in the production of matches and even in construction. In addition, phosphoric acid is used in the manufacture of cement in dental technology and is included in many medicines. This acid is quite cheap, so in some countries, such as the United States, very pure phosphoric acid, highly diluted with water, is added to refreshing drinks to replace the expensive citric acid.

Methane - CH 4. If you have a gas stove at home, then you encounter this substance every day: the natural gas that burns in the burners of your stove consists of 95% methane. Methane is a colorless and odorless gas with a boiling point of –161 o C. When mixed with air, it is explosive, which explains the explosions and fires that sometimes occur in coal mines (another name for methane is firedamp). The third name for methane - swamp gas - is due to the fact that bubbles of this particular gas rise from the bottom of swamps, where it is formed as a result of the activity of certain bacteria. In industry, methane is used as fuel and raw material for the production of other substances. Methane is the simplest hydrocarbon. This class of substances also includes ethane (C 2 H 6), propane (C 3 H 8), ethylene (C 2 H 4), acetylene (C 2 H 2) and many other substances.

Table 5.Examples of different types of formulas for some substances-

There are many repeating sequences in nature:

• Seasons;
• Times of Day;
• days of the week…

In the mid-19th century, D.I. Mendeleev noticed that the chemical properties of elements also have a certain sequence (they say that this idea came to him in a dream). The result of the scientist’s wonderful dreams was the Periodic Table of Chemical Elements, in which D.I. Mendeleev arranged chemical elements in order of increasing atomic mass. In the modern table, chemical elements are arranged in ascending order of the element's atomic number (the number of protons in the nucleus of an atom).

The atomic number is shown above the symbol of a chemical element, below the symbol is its atomic mass (the sum of protons and neutrons). Please note that the atomic mass of some elements is not a whole number! Remember isotopes! Atomic mass is the weighted average of all isotopes of an element found in nature under natural conditions.

Below the table are the lanthanides and actinides.

Metals, non-metals, metalloids

Located in the Periodic Table to the left of a stepped diagonal line that begins with Boron (B) and ends with polonium (Po) (the exceptions are germanium (Ge) and antimony (Sb). It is easy to see that metals occupy most of the Periodic Table. Basic properties of metals : hard (except mercury); shiny; good electrical and thermal conductors; plastic; malleable; easily give up electrons.

The elements located to the right of the B-Po stepped diagonal are called non-metals. The properties of non-metals are exactly the opposite of those of metals: poor conductors of heat and electricity; fragile; non-malleable; non-plastic; usually accept electrons.

Metalloids

Between metals and non-metals there are semimetals(metalloids). They are characterized by the properties of both metals and non-metals. Semimetals have found their main application in industry in the production of semiconductors, without which not a single modern microcircuit or microprocessor is conceivable.

Periods and groups

As mentioned above, the periodic table consists of seven periods. In each period, the atomic numbers of elements increase from left to right.

The properties of elements change sequentially in periods: thus sodium (Na) and magnesium (Mg), located at the beginning of the third period, give up electrons (Na gives up one electron: 1s 2 2s 2 2p 6 3s 1 ; Mg gives up two electrons: 1s 2 2s 2 2p 6 3s 2). But chlorine (Cl), located at the end of the period, takes one element: 1s 2 2s 2 2p 6 3s 2 3p 5.

In groups, on the contrary, all elements have the same properties. For example, in group IA(1), all elements from lithium (Li) to francium (Fr) donate one electron. And all elements of group VIIA(17) take one element.

Some groups are so important that they have received special names. These groups are discussed below.

Group IA(1). Atoms of elements of this group have only one electron in their outer electron layer, so they easily give up one electron.

The most important alkali metals are sodium (Na) and potassium (K), since they play an important role in human life and are part of salts.

Electronic configurations:

• Li- 1s 2 2s 1 ;
• Na- 1s 2 2s 2 2p 6 3s 1 ;
• K- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

Group IIA(2). Atoms of elements of this group have two electrons in their outer electron layer, which they also give up during chemical reactions. The most important element is calcium (Ca) - the basis of bones and teeth.

Electronic configurations:

• Be- 1s 2 2s 2 ;
• Mg- 1s 2 2s 2 2p 6 3s 2 ;
• Ca- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2

Group VIIA(17). Atoms of elements of this group usually receive one electron each, because There are five elements on the outer electronic layer and one electron is just missing from the “complete set”.

The most well-known elements of this group: chlorine (Cl) - is part of salt and bleach; Iodine (I) is an element that plays an important role in the activity of the human thyroid gland.

Electronic Configuration:

• F- 1s 2 2s 2 2p 5 ;
• Cl- 1s 2 2s 2 2p 6 3s 2 3p 5 ;
• Br- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5

Group VIII(18). Atoms of elements of this group have a fully “complete” outer electron layer. Therefore, they “don’t” need to accept electrons. And they “don’t want” to give them away. Hence, the elements of this group are very “reluctant” to enter into chemical reactions. For a long time it was believed that they do not react at all (hence the name “inert”, i.e. “inactive”). But chemist Neil Bartlett discovered that some of these gases can still react with other elements under certain conditions.

Electronic configurations:

• Ne- 1s 2 2s 2 2p 6 ;
• Ar- 1s 2 2s 2 2p 6 3s 2 3p 6 ;
• Kr- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6

Valence elements in groups

It is easy to notice that within each group the elements are similar to each other in their valence electrons (electrons of s and p orbitals located on the outer energy level).

Alkali metals have 1 valence electron:

• Li- 1s 2 2s 1 ;
• Na- 1s 2 2s 2 2p 6 3s 1 ;
• K- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

Alkaline earth metals have 2 valence electrons:

• Be- 1s 2 2s 2 ;
• Mg- 1s 2 2s 2 2p 6 3s 2 ;
• Ca- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2

Halogens have 7 valence electrons:

• F- 1s 2 2s 2 2p 5 ;
• Cl- 1s 2 2s 2 2p 6 3s 2 3p 5 ;
• Br- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5

Inert gases have 8 valence electrons:

• Ne- 1s 2 2s 2 2p 6 ;
• Ar- 1s 2 2s 2 2p 6 3s 2 3p 6 ;
• Kr- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6

For more information, see the article Valency and the Table of Electronic Configurations of Atoms of Chemical Elements by Period.

Let us now turn our attention to the elements located in groups with symbols IN. They are located in the center of the periodic table and are called transition metals.

A distinctive feature of these elements is the presence in the atoms of electrons that fill d-orbitals:

1. Sc- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 ;
2. Ti- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2

Separately from the main table are located lanthanides And actinides- these are the so-called internal transition metals. In the atoms of these elements, electrons fill f-orbitals:

1. Ce- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 4d 10 5s 2 5p 6 4f 1 5d 1 6s 2 ;
2. Th- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 4d 10 5s 2 5p 6 4f 14 5d 10 6s 2 6p 6 6d 2 7s 2

If you find the periodic table difficult to understand, you are not alone! Although it can be difficult to understand its principles, learning how to use it will help you when studying science. First, study the structure of the table and what information you can learn from it about each chemical element. Then you can begin to study the properties of each element. And finally, using the periodic table, you can determine the number of neutrons in an atom of a particular chemical element.

Steps

Part 1

Table structure

The periodic table, or periodic table of chemical elements, begins in the upper left corner and ends at the end of the last row of the table (lower right corner). The elements in the table are arranged from left to right in increasing order of their atomic number. The atomic number shows how many protons are contained in one atom. In addition, as the atomic number increases, the atomic mass also increases. Thus, by the location of an element in the periodic table, its atomic mass can be determined.

1. As you can see, each subsequent element contains one more proton than the element preceding it. This is obvious when you look at the atomic numbers. Atomic numbers increase by one as you move from left to right. Because elements are arranged in groups, some table cells are left empty.

   • For example, the first row of the table contains hydrogen, which has atomic number 1, and helium, which has atomic number 2. However, they are located on opposite edges because they belong to different groups.

2. Learn about groups that contain elements with similar physical and chemical properties. The elements of each group are located in the corresponding vertical column. They are typically identified by the same color, which helps identify elements with similar physical and chemical properties and predict their behavior. All elements of a particular group have the same number of electrons in their outer shell.

   • Hydrogen can be classified as both alkali metals and halogens. In some tables it is indicated in both groups.
   • In most cases, the groups are numbered from 1 to 18, and the numbers are placed at the top or bottom of the table. Numbers can be specified in Roman (eg IA) or Arabic (eg 1A or 1) numerals.
   • When moving along a column from top to bottom, you are said to be “browsing a group.”

3. Find out why there are empty cells in the table. Elements are ordered not only according to their atomic number, but also by group (elements in the same group have similar physical and chemical properties). Thanks to this, it is easier to understand how a particular element behaves. However, as the atomic number increases, elements that fall into the corresponding group are not always found, so there are empty cells in the table.

   • For example, the first 3 rows have empty cells because transition metals are only found from atomic number 21.
   • Elements with atomic numbers 57 to 102 are classified as rare earth elements, and are usually placed in their own subgroup in the lower right corner of the table.

4. Each row of the table represents a period. All elements of the same period have the same number of atomic orbitals in which the electrons in the atoms are located. The number of orbitals corresponds to the period number. The table contains 7 rows, that is, 7 periods.

   • For example, atoms of elements of the first period have one orbital, and atoms of elements of the seventh period have 7 orbitals.
   • As a rule, periods are designated by numbers from 1 to 7 on the left of the table.
   • As you move along a line from left to right, you are said to be “scanning the period.”

5. Learn to distinguish between metals, metalloids and non-metals. You will better understand the properties of an element if you can determine what type it is. For convenience, in most tables metals, metalloids, and nonmetals are designated by different colors. Metals are on the left and non-metals are on the right side of the table. Metalloids are located between them.

   Part 2

   Element designations

   1. Each element is designated by one or two Latin letters. As a rule, the element symbol is shown in large letters in the center of the corresponding cell. A symbol is a shortened name for an element that is the same in most languages. Element symbols are commonly used when conducting experiments and working with chemical equations, so it is helpful to remember them.

      • Typically, element symbols are abbreviations of their Latin name, although for some, especially recently discovered elements, they are derived from the common name. For example, helium is represented by the symbol He, which is close to the common name in most languages. At the same time, iron is designated as Fe, which is an abbreviation of its Latin name.

   2. Pay attention to the full name of the element if it is given in the table. This element "name" is used in regular texts. For example, "helium" and "carbon" are names of elements. Usually, although not always, the full names of the elements are listed below their chemical symbol.

      • Sometimes the table does not indicate the names of the elements and only gives their chemical symbols.

   3. Find the atomic number. Typically, the atomic number of an element is located at the top of the corresponding cell, in the middle or in the corner. It may also appear under the element's symbol or name. Elements have atomic numbers from 1 to 118.

      • The atomic number is always an integer.

   4. Remember that the atomic number corresponds to the number of protons in an atom. All atoms of an element contain the same number of protons. Unlike electrons, the number of protons in the atoms of an element remains constant. Otherwise, you would get a different chemical element!

      • The atomic number of an element can also determine the number of electrons and neutrons in an atom.

   5. Usually the number of electrons is equal to the number of protons. The exception is the case when the atom is ionized. Protons have a positive charge and electrons have a negative charge. Because atoms are usually neutral, they contain the same number of electrons and protons. However, an atom can gain or lose electrons, in which case it becomes ionized.

      • Ions have an electrical charge. If an ion has more protons, it has a positive charge, in which case a plus sign is placed after the element symbol. If an ion contains more electrons, it has a negative charge, indicated by a minus sign.
      • The plus and minus signs are not used if the atom is not an ion.

How to use the periodic table? For an uninitiated person, reading the periodic table is the same as for a gnome looking at the ancient runes of the elves. And the periodic table can tell you a lot about the world.

In addition to serving you well in the exam, it is also simply irreplaceable in solving a huge number of chemical and physical problems. But how to read it? Fortunately, today everyone can learn this art. In this article we will tell you how to understand the periodic table.

The periodic table of chemical elements (Mendeleev's table) is a classification of chemical elements that establishes the dependence of various properties of elements on the charge of the atomic nucleus.

History of the creation of the Table

Dmitry Ivanovich Mendeleev was not a simple chemist, if anyone thinks so. He was a chemist, physicist, geologist, metrologist, ecologist, economist, oil worker, aeronaut, instrument maker and teacher. During his life, the scientist managed to conduct a lot of fundamental research in various fields of knowledge. For example, it is widely believed that it was Mendeleev who calculated the ideal strength of vodka - 40 degrees.

We don’t know how Mendeleev felt about vodka, but we know for sure that his dissertation on the topic “Discourse on the combination of alcohol with water” had nothing to do with vodka and considered alcohol concentrations from 70 degrees. With all the merits of the scientist, the discovery of the periodic law of chemical elements - one of the fundamental laws of nature, brought him the widest fame.

There is a legend according to which a scientist dreamed of the periodic table, after which all he had to do was refine the idea that had appeared. But, if everything were so simple.. This version of the creation of the periodic table, apparently, is nothing more than a legend. When asked how the table was opened, Dmitry Ivanovich himself answered: “ I’ve been thinking about it for maybe twenty years, but you think: I was sitting there and suddenly... it’s done.”

In the mid-nineteenth century, attempts to arrange the known chemical elements (63 elements were known) were undertaken in parallel by several scientists. For example, in 1862, Alexandre Emile Chancourtois placed elements along a helix and noted the cyclic repetition of chemical properties.

Chemist and musician John Alexander Newlands proposed his version of the periodic table in 1866. An interesting fact is that the scientist tried to discover some kind of mystical musical harmony in the arrangement of the elements. Among other attempts, there was also Mendeleev’s attempt, which was crowned with success.

In 1869, the first table diagram was published, and March 1, 1869 is considered the day the periodic law was opened. The essence of Mendeleev's discovery was that the properties of elements with increasing atomic mass do not change monotonically, but periodically.

The first version of the table contained only 63 elements, but Mendeleev made a number of very unconventional decisions. So, he guessed to leave space in the table for still undiscovered elements, and also changed the atomic masses of some elements. The fundamental correctness of the law derived by Mendeleev was confirmed very soon, after the discovery of gallium, scandium and germanium, the existence of which was predicted by the scientist.

Modern view of the periodic table

Below is the table itself

Today, instead of atomic weight (atomic mass), the concept of atomic number (the number of protons in the nucleus) is used to order elements. The table contains 120 elements, which are arranged from left to right in order of increasing atomic number (number of protons)

The table columns represent so-called groups, and the rows represent periods. The table has 18 groups and 8 periods.

1. The metallic properties of elements decrease when moving along a period from left to right, and increase in the opposite direction.
2. The sizes of atoms decrease when moving from left to right along periods.
3. As you move from top to bottom through the group, the reducing metal properties increase.
4. Oxidizing and non-metallic properties increase as you move along a period from left to right.

What do we learn about an element from the table? For example, let's take the third element in the table - lithium, and consider it in detail.

First of all, we see the element symbol itself and its name below it. In the upper left corner is the atomic number of the element, in which order the element is arranged in the table. The atomic number, as already mentioned, is equal to the number of protons in the nucleus. The number of positive protons is usually equal to the number of negative electrons in an atom (except in isotopes).

The atomic mass is indicated under the atomic number (in this version of the table). If we round the atomic mass to the nearest integer, we get what is called the mass number. The difference between the mass number and the atomic number gives the number of neutrons in the nucleus. Thus, the number of neutrons in a helium nucleus is two, and in lithium it is four.

Our course “Periodical Table for Dummies” has ended. In conclusion, we invite you to watch a thematic video, and we hope that the question of how to use the periodic table of Mendeleev has become clearer to you. We remind you that it is always more effective to study a new subject not alone, but with the help of an experienced mentor. That is why you should never forget about the student service, which will gladly share its knowledge and experience with you.