If you find the periodic table difficult to understand, you are not alone! While it can be difficult to understand its principles, knowing how to work with it will help in the study of natural sciences. First, study the structure of the table and what information can be learned from it about each chemical element. Then you can start exploring 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 the periodic table of chemical elements, begins in the left upper corner and ends at the end of the last line of the table (in the lower right corner). Elements in the table are arranged from left to right in ascending order of their atomic number. The atomic number shows how many protons there are in one atom. In addition, with an increase in the atomic number, the atomic mass also increases. Thus, by the location of an element in the periodic table, you can determine its atomic mass.

1. As you can see, each next 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. Since the items are arranged in groups, some cells in the table remain blank.

   • 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, since they belong to different groups.

2. Learn about groups that include elements with similar physical and chemical properties. The elements of each group are arranged in a corresponding vertical column. Typically, they are indicated by the same color, which helps to identify elements with similar physical and chemical properties and predict their behavior. All elements of a particular group have the same number of electrons on the outer shell.

   • Hydrogen can be attributed both to the group of alkali metals and to the group of halogens. In some tables, it is indicated in both groups.
   • In most cases, groups are numbered from 1 to 18, and numbers are placed at the top or bottom of the table. Numbers can be specified in Roman (for example, IA) or Arabic (for example, 1A or 1) numerals.
   • Moving along the column from top to bottom is said to be "viewing the group."

3. Find out why the table contains empty cells. Elements are ordered not only according to their atomic number, but also according to groups (elements of one group have similar physical and chemical properties). This makes it easier to understand how a particular element behaves. However, as the atomic number grows, the 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, since transition metals are found only from atomic number 21.
   • Elements with atomic numbers 57 through 102 are classified as rare earth elements, and are usually listed in a separate subgroup in the lower right corner of the table.

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

   • For example, the atoms of the elements of the first period have one orbital, and the atoms of the elements of the seventh period have 7 orbitals.
   • As a rule, periods are indicated by numbers from 1 to 7 on the left of the table.
   • Moving along the line from left to right is said to be "viewing a 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 belongs to. For convenience, in most tables, metals, metalloids and non-metals are indicated by different colors. Metals are on the left and non-metals are on the right 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 an abbreviated name for an element, which is the same in most languages. When doing experiments and working with chemical equations, symbols for the elements are commonly used, so it is helpful to remember them.

      • Typically, element symbols are an abbreviation of their Latin name, although for some, especially recently discovered elements, they are derived from a common name. For example, helium is denoted 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 shown in the table. This "name" of the element is used in normal text. For example, "helium" and "carbon" are the names of the elements. Usually, though not always, full names elements are indicated under their chemical symbol.

      • Sometimes the names of the elements are not indicated in the table and only their chemical symbols are given.

   3. Find the atomic number. Usually the atomic number of an element is located at the top of the corresponding cell, in the middle or in the corner. It can also appear below the symbol or element 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 the atom. All atoms of an element contain the same number of protons. Unlike electrons, the number of protons in an element's atoms remains constant. Otherwise, another chemical element would have turned out!

      • 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. An exception is the case when the atom is ionized. Protons are positively charged and electrons are negatively charged. Since atoms are usually neutral, they contain the same number of electrons and protons. However, an atom can capture electrons or lose them, in which case it ionizes.

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

Period is a line of the periodic table of chemical elements, a sequence of atoms in accordance with the increase in the nuclear charge and the filling of the outer electron shell with electrons.

The periodic table has seven periods. The first period, containing 2 elements, as well as the second and the third, with 8 elements each, are called small. The rest of the periods with 18 or more elements are large. The seventh period has not been completed. The number of the period to which a chemical element belongs is determined by the number of its electron shells (energy levels).

The charge number of an atomic nucleus (synonyms: atomic number, atomic number, ordinal number of a chemical element) is the number of protons in an atomic nucleus. The charge number is equal to the charge of the nucleus in units of elementary charge and is at the same time equal to the ordinal number of the chemical element corresponding to the nucleus in the periodic table.

The group of the periodic system of chemical elements is a sequence of atoms with increasing nuclear charge, having the same type of electronic structure.

In the short-period version of the periodic system, the groups are subdivided into subgroups - main (or subgroups A), starting with the elements of the first and second periods, and secondary (subgroups B), containing d-elements. Subgroups are also named according to the element with the lowest nuclear charge (as a rule, according to the element of the second period for the main subgroups and the element of the fourth period for the secondary subgroups). Elements of one subgroup have similar chemical properties.

what is the period in chemistry

1. Period is a line of the periodic table of chemical elements, a sequence of atoms according to increasing nuclear charge and filling the outer electron shell with electrons.

   The periodic table has seven periods. The first period, containing 2 elements, as well as the second and the third, with 8 elements each, are called small. The rest of the periods with 18 or more elements are large. The seventh period is not over. The number of the period to which a chemical element belongs is determined by the number of its electron shells (energy levels).

   
   

   Each period (except for the first) begins with a typical metal (Li, Na, K, Rb, Cs, Fr) and ends with a noble gas (He, Ne, Ar, Kr, Xe, Rn), which is preceded by a typical non-metal.

   Zarya # 769; additional number # 769; atomic nucleus (synonyms: atomic number, atomic number, ordinal number of a chemical element) the number of protons in an atomic nucleus. The charge number is equal to the charge of the nucleus in units of elementary charge and is at the same time equal to the ordinal number of the chemical element corresponding to the nucleus in the periodic table.

   The group of the periodic system of chemical elements is a sequence of atoms with increasing nuclear charge, having the same type of electronic structure.

   The group number is determined by the number of electrons on the outer shell of the atom (valence electrons) and, as a rule, corresponds to the highest valence of the atom.

   In the short-period version of the periodic system, the groups are subdivided into main subgroups (or subgroups A), starting with the elements of the first and second periods, and secondary (subgroups B), containing d-elements. Subgroups are also named according to the element with the lowest nuclear charge (as a rule, according to the element of the second period for the main subgroups and the element of the fourth period for the secondary subgroups). Elements of one subgroup have similar chemical properties.

   With an increase in the nuclear charge of elements of one group, due to an increase in the number of electron shells, atomic radii increase, as a result of which there is a decrease in electronegativity, an increase in the metallic and non-metallic properties of elements, an increase in the reducing and weakening of the oxidizing properties of the substances formed by them.

2. Horizontal lines in tab. Mendeleev
3. Horizontal line (that sho is angry) table. Mendeleva

Evolution of the periodic table of chemical elements

The idea of ​​the place of an element in the system, introduced by Mendeleev, turned out to be special and important for the evolution of the periodic system of chemical elements; the position of the element is determined by the numbers of the period and group. Based on this idea, Mendeleev came to the conclusion that it was necessary to change the atomic weights of some elements (U, In, Ce and its analogs), which were then adopted, which was the first practical application of P. s. e., and also for the first time predicted the existence and basic properties of several unknown elements, which corresponded to empty cells P. with. NS. A classic example is the prediction of "eka-aluminum" (the future Ga, discovered by P. Lecoq de Boisabaudran in 1875), "ekabor" (Sc, discovered by the Swedish scientist L. Nilson in 1879) and "ekasilicia" (Ge, discovered by the German scientist K. Winkler in 1886). In addition, Mendeleev predicted the existence of analogues of manganese (future Tc and Re), tellurium (Po), iodine (At), cesium (Fr), barium (Ra), tantalum (Pa).

In many ways, it represented an empirical generalization of the facts, since the physical meaning of the periodic law was unclear and there was no explanation of the reasons periodic changes properties of elements depending on the increase in atomic weights.

this up to the physical substantiation of the periodic law and the development of the theory of P. with. NS. many facts could not be explained. So, unexpected was the discovery at the end of the 19th century. inert gases, which, it seemed, did not find a place in P. with. NS.; this difficulty was eliminated due to the inclusion in P. with. NS. an independent zero group (later VIIIa-subgroup). The discovery of many "radioelements" at the beginning of the 20th century. led to a contradiction between the need for their placement in P. with. NS. and its structure (for more than 30 such elements there were 7 “vacancies” in the sixth and seventh periods). This contradiction was overcome as a result of the discovery of isotopes. Finally, the value of atomic weight (atomic mass) as a parameter that determines the properties of elements gradually lost its value.

The structure of the periodic table of chemical elements.

Modern (1975) P. s. NS. covers 106 chemical elements; of these, all transuranic (Z = 93-106), as well as elements with Z = 43 (Tc), 61 (Pm), 85 (At), and 87 (Fr), were obtained artificially. Throughout the history of P. s. NS. was asked a large number of(several hundred) options for its graphic representation, mainly in the form of tables; images are also known in the form of various geometric shapes (spatial and planar), analytical curves (for example, spirals), etc. The most widespread are three forms of P.

BC: short, proposed by Mendeleev (Fig. 2) and received universal recognition (in modern form it is given in Fig.); long (fig. 3); staircase (Fig. 4). The long form was also developed by Mendeleev, and in an improved form it was proposed in 1905 by A. Werner. The staircase form was proposed by the English scientist T. Bailey (1882), the Danish scientist J. Thomsen (1895), and improved by N. Bohr (1921). Each of the three forms has advantages and disadvantages. The fundamental principle of constructing P. with. NS. is the division of all chemical elements into groups and periods. Each group, in turn, is subdivided into main (a) and secondary (b) subgroups. Each subgroup contains elements with similar chemical properties. Elements of a- and b-subgroups in each group, as a rule, exhibit a certain chemical similarity among themselves, mainly in higher oxidation states, which, as a rule, correspond to the group number. A period is called a set of elements, beginning with an alkali metal and ending with an inert gas (a special case is the first period); each period contains a strictly defined number of elements. P. s. NS. consists of 8 groups and 7 periods (the seventh is not yet completed).

The first period of the periodic table of elements

The specificity of the first period is that it contains only 2 elements: H and He. The place of H in the system is ambiguous: hydrogen exhibits properties in common with alkali metals and with halogens; it is placed either in the Ia- or (preferably) in the VIIa-subgroup. Helium is the first representative of the VIIa-subgroup (however, for a long time, He and all inert gases were combined into an independent zero group).

The second period of the periodic table of elements

The second period (Li - Ne) contains 8 elements. It begins with an alkali metal Li, the only oxidation state of which is I. Then comes Be - a metal, oxidation state II. The metallic character of the next element B is weakly expressed (oxidation state III). The C following it is a typical non-metal, it can be either positively or negatively tetravalent. Subsequent N, O, F and Ne are non-metals, and only N has the highest oxidation state V corresponding to the group number; oxygen only in rare cases exhibits a positive valence, and the oxidation state VI is known for F. The period ends with the inert gas Ne.

The third period of the periodic table of elements

The third period (Na - Ar) also contains 8 elements, the nature of the change in the properties of which is in many respects similar to that observed in the second period. However, Mg, in contrast to Be, is more metallic, as is Al compared to B, although Al is amphoteric. Si, P, S, Cl, Ar are typical non-metals, but all of them (except for Ar) exhibit the highest oxidation states equal to the group number. Thus, in both periods, as Z increases, there is a weakening of the metallic character and an increase in the non-metallic character of the elements. Mendeleev called the elements of the second and third periods (small, in his terminology) typical. It is essential that they are among the most widespread in nature, and C, N and O are, along with H, the main elements of organic matter (organogens). All elements of the first three periods are included in subgroups a.

Modern terminology - the elements of these periods refer to the s-elements (alkali and alkaline-earth metals), which make up the Ia- and IIa-subgroups (highlighted on the colored table in red), and the p-elements (B - Ne, At - Ar), included in IIIa - VIIIa-subgroups (their symbols are highlighted in orange). For elements of small periods, with increasing ordinal numbers, at first a decrease in atomic radii is observed, and then, when the number of electrons in the outer shell of an atom already significantly increases, their mutual repulsion leads to an increase in atomic radii. The next maximum is reached at the beginning of the next period on an alkaline element. Approximately the same pattern is typical for ionic radii.

The fourth period of the periodic table of elements

The fourth period (K - Kr) contains 18 elements (the first large period, according to Mendeleev). After the alkali metal K and alkaline earth Ca (s-elements), there follows a series of ten so-called transition elements (Sc - Zn), or d-elements (symbols are given in blue), which are included in subgroups b of the corresponding groups of P. s. NS. Most of the transition elements (all of them are metals) exhibit the highest oxidation states equal to the group number. An exception is the Fe - Co - Ni triad, where two last items are maximally positively trivalent, and iron under certain conditions is known in the VI oxidation state. Elements starting with Ga and ending with Kr (p-elements) belong to subgroups a, and the nature of the change in their properties is the same as in the corresponding intervals Z for elements of the second and third periods. It was found that Kr is capable of forming chemical compounds (mainly with F), but the oxidation state VIII is unknown for it.

Fifth period of the periodic table of elements

The fifth period (Rb - Xe) is built similarly to the fourth; it also has an insert of 10 transition elements (Y - Cd), d-elements. Specific features of the period: 1) in the Ru - Rh - Pd triad, only ruthenium exhibits oxidation state VIII; 2) all elements of subgroups a exhibit the highest oxidation states equal to the group number, including Xe; 3) I have weak metallic properties. Thus, the nature of the change in properties with an increase in Z in elements of the fourth and fifth periods is more complicated, since the metallic properties are preserved in a wide range of ordinal numbers.

Sixth Period of the Periodic Table of Elements

The sixth period (Cs - Rn) includes 32 elements. In addition to 10 d-elements (La, Hf - Hg), it contains a set of 14 f-elements, lanthanides, from Ce to Lu (black symbols). The elements from La to Lu are chemically very similar. In P.'s short form with. NS. lanthanides are incorporated into the La cell (since their predominant oxidation state is III) and are recorded on a separate line at the bottom of the table. This technique is somewhat inconvenient, since 14 elements appear to be outside the table. The long and ladder forms of P. are deprived of a similar disadvantage. BC, well reflecting the specificity of lanthanides against the background of the integral structure of P. with. NS. Peculiarities of the period: 1) in the Os - Ir - Pt triad, only osmium exhibits oxidation state VIII; 2) At has a more pronounced (in comparison with 1) metallic character; 3) Rn, apparently (its chemistry has been little studied), should be the most reactive of the inert gases.

The fourth period of the periodic table includes the elements of the fourth line (or fourth period) of the periodic table of chemical elements. The structure of the periodic table is based on strings to illustrate repetitive (periodic) ... ... Wikipedia

The fifth period of the periodic system includes the elements of the fifth line (or fifth period) of the periodic table of chemical elements. The structure of the periodic table is based on strings to illustrate recurring (periodic) trends in ... ... Wikipedia

The seventh period of the periodic table includes the elements of the seventh row (or seventh period) of the periodic table of chemical elements. The structure of the periodic table is based on strings to illustrate repeating (periodic) trends ... Wikipedia

The sixth period of the periodic system includes the elements of the sixth line (or sixth period) of the periodic system of chemical elements. The structure of the periodic table is based on strings to illustrate recurring (periodic) trends in ... ... Wikipedia

The first period of the periodic system includes the elements of the first line (or first period) of the periodic system of chemical elements. The structure of the periodic table is based on strings to illustrate recurring (periodic) trends in ... ... Wikipedia

The elements of the second line (or second period) of the periodic table of chemical elements belong to the second period of the periodic system. The structure of the periodic table is based on strings to illustrate recurring (periodic) trends in ... Wikipedia

The third period of the periodic system includes the elements of the third line (or third period) of the periodic system of chemical elements. The structure of the periodic table is based on strings to illustrate repeating (periodic) trends ... Wikipedia

Includes hypothetical chemical elements belonging to the additional eighth line (or period) of the periodic table. The systematic names of these elements have been handed over to IUPAC for use. None of these elements have yet been ... ... Wikipedia

Period is a line of the periodic table of chemical elements, a sequence of atoms according to increasing nuclear charge and filling the outer electron shell with electrons. The periodic table has seven periods. The first period containing 2 elements ... Wikipedia

The short form of the periodic table is based on the parallelism of the oxidation states of the elements of the main and secondary subgroups: for example, maximum degree vanadium oxidation is +5, like phosphorus and arsenic, the maximum oxidation state of chromium is +6 ... Wikipedia

Books

• S. Yu. Witte. Collected works and documentary materials. In 5 volumes. Volume 3. Book 2, S. Yu. Witte. The second book of the third volume of the edition includes the most important documentary materials, official notes, publications and articles on the monetary reform and the monetary system in Russia, which constituted ...
• Periodicals and censorship of the Russian Empire in 1865-1905. The system of administrative penalties,. The book examines the censorship policy of the Russian government in relation to periodicals at a time when the role of the latter in the life of society was becoming more and more influential. ...

A sequence of atoms in order to increase the nuclear charge and fill the outer electron shell with electrons.

The periodic table has seven periods. The first period, containing 2 elements, as well as the second and third, with 8 elements each, are called small... The rest of the periods with 18 or more elements - large... The seventh period is over. The eighth period is not completed. The number of the period to which a chemical element belongs is determined by the number of its electron shells (energy levels).

Each period (except for the first) begins with a typical metal (, Na,,,,) and ends with a noble gas (,,, Xe,,), which is preceded by a typical non-metal.

In the first period, apart from helium, there is only one element - hydrogen, combining properties typical both for metals and (to a greater extent) for non-metals. These elements are filled with electrons 1 s-shell.

Elements of the second and third periods are sequentially filled s- and R-shells. For elements of small periods, a rather rapid increase in electronegativity with an increase in nuclear charges, a weakening of metallic properties and an increase in nonmetallic properties are characteristic.

The fourth and fifth periods contain decades of transition d-elements (from scandium to zinc and from yttrium to cadmium), in which, after filling with electrons, the external s-subshells are filled in according to the Klechkovsky rule, d- a subshell of the previous energy level.

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 6f 7d 7f ...

In the sixth and seventh periods saturation occurs 4 f- and 5 f- subshells, as a result of which they contain another 14 elements more compared to the 4th and 5th periods (lanthanides in the sixth and actinides in the seventh period).

Due to the difference in periods in length and other characteristics, there are different ways their relative location in the periodic table. In the short-period version, the small periods contain one a number of elements, large have two rows. In the long-period variant, all periods consist of one row. The series of lanthanides and actinides are usually recorded separately at the bottom of the table.

Elements of the same period have close values ​​of atomic masses, but different physical and chemical properties, in contrast to elements of the same