Chemical elements of the periodic system. Periodic system of Mendeleev
In nature, there are a lot of repeating sequences:
- seasons;
- Times of Day;
- days of the week…
In the middle of the 19th century, D.I. Mendeleev noticed that Chemical properties elements also have a certain sequence (it is said that this idea came to him in a dream). The result of the miraculous dreams of the scientist was the Periodic Table of Chemical Elements, in which D.I. Mendeleev arranged the chemical elements in ascending order atomic mass. In the modern table, the chemical elements are arranged in ascending order of the atomic number of the element (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). Note that the atomic mass of some elements is a non-integer! Remember isotopes! Atomic mass is the weighted average of all the isotopes of an element that occur naturally under natural conditions.
Below the table are the lanthanides and actinides.
Metals, non-metals, metalloids
They are located in the Periodic Table to the left of the stepped diagonal line that starts 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 Periodic table. Basic properties of metals: solid (except mercury); glitter; good electrical and thermal conductors; plastic; malleable; donate electrons easily.
The elements to the right of the stepped diagonal B-Po are called non-metals. The properties of non-metals are directly opposite to the properties of metals: poor conductors of heat and electricity; fragile; non-forged; non-plastic; usually accept electrons.
Metalloids
Between metals and non-metals are semimetals(metalloids). They are characterized by the properties of both metals and non-metals. Semimetals have found their main industrial application in the production of semiconductors, without which no modern microcircuit or microprocessor is inconceivable.
Periods and groups
As mentioned above, the periodic table consists of seven periods. In each period, the atomic numbers of the elements increase from left to right.
The properties of elements in periods change sequentially: so sodium (Na) and magnesium (Mg), which are 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 the IA(1) group, 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 been given special names. These groups are discussed below.
Group IA(1). The atoms of the elements of this group have only one electron in the outer electron layer, so they easily donate one electron.
The most important alkali metals are sodium (Na) and potassium (K) as they play important role in the process of human life and are part of the 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). The atoms of the elements of this group have two electrons in the outer electron layer, which 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 the elements of this group usually receive one electron each, because. on the outer electronic layer there are five elements each, and one electron is just missing to the "complete set".
The most famous elements of this group are: 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 the elements of this group have a fully "staffed" outer electron layer. Therefore, they "do not 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 Barlett discovered that some of these gases, under certain conditions, can still react with other elements.
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 see 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 each:
- 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 periods.
Let us now turn our attention to the elements located in groups with symbols AT. They are located in the center of the periodic table and are called transition metals.
A distinctive feature of these elements is the presence of electrons in atoms that fill d-orbitals:
- sc- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 ;
- Ti- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2
Separate from the main table are located lanthanides and actinides are the so-called internal transition metals. In the atoms of these elements, electrons fill f-orbitals:
- 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 ;
- 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
The properties of chemical elements allow them to be combined into appropriate groups. On this principle, a periodic system was created that changed the idea of existing substances and made it possible to assume the existence of new, previously unknown elements.
In contact with
Periodic system of Mendeleev
The Periodic Table of Chemical Elements was compiled by D. I. Mendeleev in the second half of the 19th century. What is it, and why is it needed? It combines all the chemical elements in order of increasing atomic weight, and all of them are arranged so that their properties change in a periodic manner.
Mendeleev's periodic system brought into a single system all the existing elements that were previously considered simply separate substances.
Based on its study, new chemicals were predicted and subsequently synthesized. The significance of this discovery for science cannot be overestimated., it was far ahead of its time and gave impetus to the development of chemistry for many decades.
There are three most common table options, which are conventionally referred to as "short", "long" and "extra long". ». The main table is considered to be a long table, it approved officially. The difference between them is the layout of the elements and the length of the periods.
What is a period
The system contains 7 periods. They are represented graphically as horizontal lines. In this case, the period can have one or two lines, called rows. Each subsequent element differs from the previous one by increasing the nuclear charge (the number of electrons) by one.
Put simply, a period is a horizontal row in the periodic table. Each of them begins with a metal and ends with an inert gas. Actually, this creates periodicity - the properties of elements change within one period, repeating again in the next. The first, second and third periods are incomplete, they are called small and contain 2, 8 and 8 elements, respectively. The rest are complete, they have 18 elements each.
What is a group
Group is a vertical column, containing elements with the same electronic structure or, to put it simply, with the same higher . The officially approved long table contains 18 groups that start with alkali metals and end with inert gases.
Each group has its own name, which makes it easier to find or classify elements. The metallic properties are enhanced regardless of the element in the direction from top to bottom. This is due to an increase in the number of atomic orbits - the more there are, the weaker the electronic bonds, which makes the crystal lattice more pronounced.
Metals in the periodic table
Metals in the table Mendeleev have a predominant number, their list is quite extensive. They are characterized by common features, they are heterogeneous in properties and are divided into groups. Some of them have little in common with metals in the physical sense, while others can only exist for fractions of a second and are absolutely not found in nature (at least on the planet), because they were created, more precisely, calculated and confirmed in the laboratory, artificially. Each group has its own characteristics, the name is quite noticeably different from the others. This difference is especially pronounced in the first group.
The position of the metals
What is the position of metals in the periodic table? Elements are arranged by increasing atomic mass, or the number of electrons and protons. Their properties change periodically, so there is no neat one-to-one placement in the table. How to determine metals, and is it possible to do this according to the periodic table? In order to simplify the question, a special trick was invented: conditionally, a diagonal line is drawn from Bor to Polonius (or to Astatine) at the junctions of the elements. Those on the left are metals, those on the right are non-metals. It would be very simple and great, but there are exceptions - Germanium and Antimony.
Such a “method” is a kind of cheat sheet, it was invented only to simplify the memorization process. For a more accurate representation, remember that the list of non-metals is only 22 elements, therefore, answering the question of how many metals are contained in the periodic table
In the figure, you can clearly see which elements are non-metals and how they are arranged in the table by groups and periods.
General physical properties
There are general physical properties of metals. These include:
- Plastic.
- characteristic brilliance.
- Electrical conductivity.
- High thermal conductivity.
- Everything except mercury is in a solid state.
It should be understood that the properties of metals are very different with respect to their chemical or physical nature. Some of them bear little resemblance to metals in the ordinary sense of the term. For example, mercury occupies a special position. It is under normal conditions in liquid state, does not have a crystal lattice, the presence of which owes its properties to other metals. The properties of the latter in this case are conditional; mercury is related to them to a greater extent by chemical characteristics.
Interesting! Elements of the first group, alkali metals, do not occur in their pure form, being in the composition of various compounds.
The softest metal that exists in nature - cesium - belongs to this group. He, like other alkaline similar substances, has little in common with more typical metals. Some sources claim that in fact, the softest metal is potassium, which is difficult to dispute or confirm, since neither one nor the other element exists on its own - being released as a result of a chemical reaction, they quickly oxidize or react.
The second group of metals - alkaline earth - is much closer to the main groups. The name "alkaline earth" comes from ancient times, when oxides were called "earths" because they have a loose crumbly structure. More or less familiar (in the everyday sense) properties are possessed by metals starting from the 3rd group. As the group number increases, the amount of metals decreases., being replaced by non-metallic elements. Last group consists of inert (or noble) gases.
Definition of metals and non-metals in the periodic table. Simple and complex substances.
Simple substances (metals and non-metals)
Conclusion
The ratio of metals and non-metals in the periodic table clearly outweighs in favor of the former. This situation indicates that the group of metals is combined too broadly and requires a more detailed classification, which is recognized by the scientific community.
> Periodic table
Characteristics and structure Mendeleev's periodic table of chemical elements a: the position of the elements, the distribution system, the atomic number of the element.
Periodic table- the arrangement of chemical elements, based on their electronic configurations and repeating chemical characteristics Oh.
Learning task
- Understand how to periodic table chemical elements are located.
Key Points
- The periodic table is the main basis for characterizing the chemical behavior of elements.
- The table contains only those chemical elements that have a unique atomic number (the number of protons in the nucleus).
- The primacy of the publication of the first table is assigned to Dmitri Mendeleev.
Terms
- Element - any of the simplest chemical substances, which cannot be decomposed in a chemical reaction or by a chemical agent.
- The Periodic Table is a diagram of the chemical elements arranged according to their atomic numbers.
- Atomic number - a number equal to the number of protons, characterizing the chemical properties (Z).
The Periodic Table is a list of chemical elements arranged based on their atomic numbers, electronic configurations, and overlapping chemical characteristics. Elements are presented according to atomic number in ascending order. What does the structure of the periodic table look like? The standard form of the table accommodates an 18 x 7 grid. It can be deconstructed into 4 rectangular blocks: s for the left, p for the right, d for the middle, and f for the bottom of the last one. Table rows are periods. Columns s-, d- and p- are called groups, some of which have own names(e.g. halogens or noble gases).
The periodic table accommodates recurring trends, so it can be used to establish relationships between the characteristics of the elements. This also makes it possible to predict elements that have not yet been discovered. As a result, it can be used to analyze chemical behavior.
The standard form of the periodic table, in which the colors represent the different categories of elements
Features of the periodic table
Let's analyze the properties and characteristics of the periodic table of chemical elements. All varieties of the periodic table contain only chemical elements. Each has a unique atomic number - the number of protons in the nucleus. Many elements have a different number of neutrons - isotopes. For example, carbon has three naturally occurring isotopes. All its atoms have six protons, most of which have six neutrons and about 1% - 7 neutrons. In the table, isotopes are never divided, as they are grouped under one element. If the elements are devoid of stable isotopes, then they are endowed with a mass belonging to the most stable (indicated in brackets).
Scientists have managed to detect or synthesize all elements of atomic numbers from 1 (hydrogen) to 118 (oganesson). But even beyond the last element, new ones continue to be created. There is still debate about whether new ones should be added to the table.
Despite the fact that earlier tables are also known, the first publication was the version of Dmitry Mendeleev in 1869. He created it in order to show periodic trends in the characteristics of certain elements. He also managed to predict the properties of those not yet found, which were recorded in the table after him. With the advent of new elements, it was expanded and supplemented.
Mendeleev's periodic table (1869) displays periods vertically and groups horizontally
Known for illuminating the periodic table of elements
The periodic table is one of greatest discoveries humanity, which made it possible to streamline knowledge about the world around us and discover new chemical elements. It is necessary for schoolchildren, as well as for everyone who is interested in chemistry. In addition, this scheme is indispensable in other areas of science.
This diagram contains all known to man elements, and they are grouped according to atomic mass and serial number. These characteristics affect the properties of the elements. In total, there are 8 groups in the short version of the table, the elements included in one group have very similar properties. The first group contains hydrogen, lithium, potassium, copper, the Latin pronunciation in Russian of which is cuprum. And also argentum - silver, cesium, gold - aurum and francium. The second group contains beryllium, magnesium, calcium, zinc, followed by strontium, cadmium, barium, and the group ends with mercury and radium.
The third group includes boron, aluminum, scandium, gallium, then yttrium, indium, lanthanum, and the group ends with thallium and actinium. The fourth group begins with carbon, silicon, titanium, continues with germanium, zirconium, tin, and ends with hafnium, lead, and rutherfordium. In the fifth group there are elements such as nitrogen, phosphorus, vanadium, arsenic, niobium, antimony are located below, then bismuth tantalum comes and completes the dubnium group. The sixth begins with oxygen, followed by sulfur, chromium, selenium, then molybdenum, tellurium, then tungsten, polonium and seaborgium.
In the seventh group, the first element is fluorine, followed by chlorine, manganese, bromine, technetium, followed by iodine, then rhenium, astatine and borium. The last group is the most numerous. It includes gases such as helium, neon, argon, krypton, xenon and radon. This group also includes the metals iron, cobalt, nickel, rhodium, palladium, ruthenium, osmium, iridium, platinum. Next come hannium and meitnerium. Separately located elements that form the actinide series and the lanthanide series. They have similar properties to lanthanum and actinium.
This scheme includes all types of elements, which are divided into 2 large groups – metals and non-metals with different properties. How to determine whether an element belongs to a particular group, a conditional line will help, which must be drawn from boron to astatine. It should be remembered that such a line can only be drawn in full version tables. All elements that are above this line and are located in the main subgroups are considered non-metals. And which are lower, in the main subgroups - metals. Also, metals are substances that are in side subgroups. There are special pictures and photos on which you can get acquainted with the position of these elements in detail. It is worth noting that those elements that are on this line exhibit the same properties of both metals and non-metals.
A separate list is also made up of amphoteric elements, which have dual properties and can form 2 types of compounds as a result of reactions. At the same time, they manifest equally both basic and acid properties . The predominance of certain properties depends on the reaction conditions and the substances with which the amphoteric element reacts.
It should be noted that this scheme in the traditional execution of good quality is color. Wherein different colors for ease of orientation are marked main and secondary subgroups. And also elements are grouped depending on the similarity of their properties.
However, at present, along with the color scheme, the black-and-white periodic table of Mendeleev is very common. This form is used for black and white printing. Despite the apparent complexity, working with it is just as convenient, given some of the nuances. So, in this case, it is possible to distinguish the main subgroup from the secondary one by differences in shades that are clearly visible. In addition, in the color version, elements with the presence of electrons on different layers are indicated different colors.
It is worth noting that in a single-color design it is not very difficult to navigate the scheme. For this, the information indicated in each individual cell of the element will be enough.
The exam today is the main type of test at the end of school, which means that special attention must be paid to preparing for it. Therefore, when choosing final exam in chemistry, you need to pay attention to the materials that can help in its delivery. As a rule, students are allowed to use some tables during the exam, in particular, the periodic table in good quality. Therefore, in order for it to bring only benefit in tests, attention should be paid in advance to its structure and the study of the properties of the elements, as well as their sequence. You also need to learn use the black and white version of the table so that you don't face any difficulties in the exam.
In addition to the main table characterizing the properties of elements and their dependence on atomic mass, there are other schemes that can help in the study of chemistry. For example, there are tables of solubility and electronegativity of substances. The first one can determine how soluble a particular compound is in water at ordinary temperature. In this case, anions are located horizontally - negatively charged ions, and cations, that is, positively charged ions, are located vertically. To find out degree of solubility of one or another compound, it is necessary to find its components in the table. And at the place of their intersection there will be the necessary designation.
If it is the letter "r", then the substance is completely soluble in water under normal conditions. In the presence of the letter "m" - the substance is slightly soluble, and in the presence of the letter "n" - it almost does not dissolve. If there is a “+” sign, the compound does not form a precipitate and reacts with the solvent without residue. If a "-" sign is present, it means that such a substance does not exist. Sometimes you can also see the “?” sign in the table, then this means that the degree of solubility of this compound is not known for certain. Electronegativity of the elements can vary from 1 to 8, there is also a special table to determine this parameter.
Another useful table is the metal activity series. All metals are located in it in increasing degree electrochemical potential. A series of stress metals begins with lithium, ends with gold. It is believed that the further to the left a metal occupies in this row, the more active it is in chemical reactions. In this way, the most active metal Lithium is considered to be an alkaline metal. Hydrogen is also present at the end of the list of elements. It is believed that the metals that are located after it are practically inactive. Among them are elements such as copper, mercury, silver, platinum and gold.
Periodic table pictures in good quality
This scheme is one of the greatest achievements in the field of chemistry. Wherein There are many types of this table.- a short version, a long one, as well as an extra long one. The most common is the short table, and the long version of the schema is also common. It is worth noting that the short version of the scheme is not currently recommended by IUPAC for use.
Total was more than a hundred types of tables have been developed, differing in presentation, shape and graphical representation. They are used in various fields of science, or not used at all. Currently, new circuit configurations continue to be developed by researchers. As the main option, either a short or a long circuit in excellent quality is used.
The graphic representation of the Periodic Law is the Periodic System (table). The horizontal rows of the system are called periods, and the vertical columns are called groups.
In total, there are 7 periods in the system (table), and the period number is equal to the number of electron layers in the atom of the element, the number of the external (valence) energy level, and the value of the main quantum number for the highest energy level. Each period (except the first) begins with an s-element - an active alkali metal and ends with an inert gas, which is preceded by a p-element - an active non-metal (halogen). If we move along the period from left to right, then with an increase in the charge of the nuclei of atoms of chemical elements of small periods, the number of electrons at the external energy level will increase, as a result of which the properties of the elements change - from typically metallic (because there is an active alkali metal at the beginning of the period), through amphoteric (the element exhibits the properties of both metals and non-metals) to non-metallic (active non-metal - halogen at the end of the period), i.e. metallic properties gradually weaken and non-metallic ones increase.
In large periods, with increasing nuclear charge, the filling of electrons is more difficult, which explains a more complex change in the properties of elements compared to elements of small periods. So, in even rows of long periods, with increasing nuclear charge, the number of electrons in the outer energy level remains constant and equal to 2 or 1. Therefore, while the next level after the outer (second from the outside) is filled with electrons, the properties of elements in even rows change slowly. When moving to odd rows, with an increase in the nuclear charge, the number of electrons in the external energy level increases (from 1 to 8), the properties of the elements change in the same way as in small periods.
DEFINITION
Vertical columns in the Periodic system are groups of elements with a similar electronic structure and are chemical analogues. Groups are designated by Roman numerals from I to VIII. The main (A) and secondary (B) subgroups are distinguished, the first of which contain s- and p-elements, the second - d - elements.
The subgroup number A indicates the number of electrons in the outer energy level (the number of valence electrons). For elements of B-subgroups, there is no direct relationship between the group number and the number of electrons in the outer energy level. In A-subgroups, the metallic properties of the elements increase, and the non-metallic properties decrease with increasing charge of the nucleus of the element's atom.
There is a relationship between the position of the elements in the Periodic system and the structure of their atoms:
- atoms of all elements of the same period have an equal number of energy levels, partially or completely filled with electrons;
— atoms of all elements of A subgroups have an equal number of electrons at the external energy level.
A plan for characterizing a chemical element based on its position in the Periodic Table
Usually, a characteristic of a chemical element based on its position in the Periodic system is given according to the following plan:
- indicate the symbol of the chemical element, as well as its name;
- indicate the serial number, number of the period and group (type of subgroup) in which the element is located;
- indicate the nuclear charge, mass number, number of electrons, protons and neutrons in the atom;
- write down the electronic configuration and indicate the valence electrons;
- draw electron-graphic formulas for valence electrons in the ground and excited (if possible) states;
- indicate the family of the element, as well as its type (metal or non-metal);
- compare the properties of a simple substance with the properties simple substances, formed by elements neighboring in the subgroup;
- compare the properties of a simple substance with the properties of simple substances formed by elements neighboring in a period;
- indicate the formulas of higher oxides and hydroxides with brief description their properties;
- indicate the values of the minimum and maximum oxidation states of a chemical element.
Characteristics of a chemical element using magnesium (Mg) as an example
Consider the characteristics of a chemical element using the example of magnesium (Mg) according to the plan described above:
1. Mg - magnesium.
2. Ordinal number - 12. The element is in period 3, in group II, A (main) subgroup.
3. Z=12 (nuclear charge), M=24 (mass number), e=12 (number of electrons), p=12 (number of protons), n=24-12=12 (number of neutrons).
4. 12 Mg 1s 2 2s 2 2p 6 3s 2 – electronic configuration, valence electrons 3s 2 .
5. Basic state
excited state
6. s-element, metal.
7. The highest oxide - MgO - exhibits the main properties:
MgO + H 2 SO 4 \u003d MgSO 4 + H 2 O
MgO + N 2 O 5 \u003d Mg (NO 3) 2
As a magnesium hydroxide, the base Mg (OH) 2 corresponds, which exhibits all the typical properties of bases:
Mg(OH) 2 + H 2 SO 4 = MgSO 4 + 2H 2 O
8. The degree of oxidation "+2".
9. The metallic properties of magnesium are more pronounced than those of beryllium, but weaker than those of calcium.
10. The metallic properties of magnesium are less pronounced than those of sodium, but stronger than those of aluminum (neighboring elements of the 3rd period).
Examples of problem solving
EXAMPLE 1
Exercise | Characterize the chemical element sulfur based on its position in the Periodic Table of D.I. Mendeleev |
Solution | 1. S - sulfur. 2. Ordinal number - 16. The element is in the 3rd period, in the VI group, A (main) subgroup. 3. Z=16 (nuclear charge), M=32 (mass number), e=16 (number of electrons), p=16 (number of protons), n=32-16=16 (number of neutrons). 4. 16 S 1s 2 2s 2 2p 6 3s 2 3p 4 – electronic configuration, valence electrons 3s 2 3p 4 . 5. Basic state
excited state
6. p-element, non-metal. 7. The highest oxide - SO 3 - exhibits acidic properties: SO 3 + Na 2 O \u003d Na 2 SO 4 8. The hydroxide corresponding to the higher oxide - H 2 SO 4, exhibits acidic properties: H 2 SO 4 + 2NaOH \u003d Na 2 SO 4 + 2H 2 O 9. Minimum oxidation state "-2", maximum - "+6" 10. The non-metallic properties of sulfur are less pronounced than those of oxygen, but stronger than those of selenium. 11. The non-metallic properties of sulfur are more pronounced than those of phosphorus, but weaker than those of chlorine (adjacent elements in the 3rd period). |
EXAMPLE 2
Exercise | Describe the chemical element sodium based on its position in the Periodic Table of D.I. Mendeleev |
Solution | 1. Na - sodium. 2. Ordinal number - 11. The element is in period 3, in group I, A (main) subgroup. 3. Z=11 (nuclear charge), M=23 (mass number), e=11 (number of electrons), p=11 (number of protons), n=23-11=12 (number of neutrons). 4. 11 Na 1s 2 2s 2 2p 6 3s 1 – electronic configuration, valence electrons 3s 1 . 5. Basic state 6. s-element, metal. 7. The highest oxide - Na 2 O - exhibits the main properties: Na 2 O + SO 3 \u003d Na 2 SO 4 As sodium hydroxide, the base NaOH corresponds, which exhibits all the typical properties of bases: 2NaOH + H 2 SO 4 \u003d Na 2 SO 4 + 2H 2 O 8. The oxidation state "+1". 9. The metallic properties of sodium are more pronounced than those of lithium, but weaker than those of potassium. 10. The metallic properties of sodium are more pronounced than those of magnesium (the neighboring element of the 3rd period). |