For some time now, in TheBat (it is not clear for what reason), the built-in certificate database for SSL has ceased to work correctly.

When checking the post, an error pops up:

Unknown CA certificate
The server did not present a root certificate in the session and the corresponding root certificate was not found in the address book.
This connection cannot be secret. Please
contact your server administrator.

And it is offered a choice of answers - YES / NO. And so every time you shoot mail.

Solution

In this case, you need to replace the S/MIME and TLS implementation standard with Microsoft CryptoAPI in TheBat!

Since I needed to merge all the files into one, I first converted everything doc files into a single pdf file (using the Acrobat program), and then transferred to fb2 through an online converter. You can also convert files individually. Formats can be absolutely any (source) and doc, and jpg, and even zip archive!

The name of the site corresponds to the essence:) Online Photoshop.

Update May 2015

I found another great site! Even more convenient and functional for creating a completely arbitrary collage! This site is http://www.fotor.com/ru/collage/ . Use on health. And I will use it myself.

Faced in life with the repair of electric stoves. I already did a lot of things, learned a lot, but somehow I had little to do with tiles. It was necessary to replace the contacts on the regulators and burners. The question arose - how to determine the diameter of the burner on the electric stove?

The answer turned out to be simple. No need to measure anything, you can calmly determine by eye what size you need.

The smallest burner is 145 millimeters (14.5 centimeters)

Medium burner is 180 millimeters (18 centimeters).

And finally the most large burner is 225 millimeters (22.5 centimeters).

It is enough to determine the size by eye and understand what diameter you need a burner. When I didn’t know this, I was soaring with these sizes, I didn’t know how to measure, which edge to navigate, etc. Now I'm wise :) I hope it helped you too!

In my life I faced such a problem. I think I'm not the only one.

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

In addition to serving you in the exam, it is also simply indispensable in solving problems. huge amount 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 system 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

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

We do not know how Mendeleev treated vodka, but it is known 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 the scientist dreamed of the periodic system, after which he only had to finalize 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, and you think: I sat and suddenly ... it’s ready. ”

In the middle of the nineteenth century, attempts to streamline the known chemical elements (63 elements were known) were simultaneously undertaken by several scientists. For example, in 1862 Alexandre Émile Chancourtois placed the elements along a helix and noted the cyclical repetition of chemical properties.

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

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

The first version of the table contained only 63 elements, but Mendeleev made a number of very non-standard decisions. So, he guessed to leave a place in the table for yet 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 scientists.

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 ascending order of atomic number (number of protons)

The columns of the table are so-called groups, and the rows are periods. There are 18 groups and 8 periods in the table.

1. The metallic properties of elements decrease when moving along the period from left to right, and increase in the opposite direction.
2. The dimensions of atoms decrease as they move from left to right along the periods.
3. When moving from top to bottom in the group, the reducing metallic properties increase.
4. Oxidative and non-metallic properties increase as you move along the period from left to right.

What do we learn about the 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 symbol of the element itself and its name under it. In the upper left corner is the atomic number of the element, in the order in which the element is located 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 (with the exception of 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 the so-called 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 - four.

So our course "Mendeleev's 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 more clear to you. We remind you that learning a new subject is always more effective not alone, but with the help of an experienced mentor. That is why, you should never forget about, who will gladly share his knowledge and experience with you.

How it all began?

Many well-known eminent chemists at the turn of the 19th-20th centuries have long noticed that the physical and chemical properties of many chemical elements are very similar to each other. For example, Potassium, Lithium and Sodium are all active metals, which, when interacting with water, form active hydroxides of these metals; Chlorine, Fluorine, Bromine in their compounds with hydrogen showed the same valence equal to I and all these compounds are strong acids. From this similarity, the conclusion has long been suggested that all known chemical elements can be combined into groups, and so that the elements of each group have a certain set of physicochemical characteristics. However, often such groups were incorrectly compiled from different elements by various scientists, and for a long time one of the main characteristics of the elements was ignored by many - this is their atomic mass. It was ignored because it was and is different for different elements, which means it could not be used as a parameter for grouping. The only exception was the French chemist Alexander Emile Chancourtua, who tried to arrange all the elements in a three-dimensional model along a helix, but his work was not recognized by the scientific community, and the model turned out to be cumbersome and inconvenient.

Unlike many scientists, D.I. Mendeleev took the atomic mass (in those days, even " Atomic weight") as a key parameter in the classification of elements. In his version, Dmitry Ivanovich arranged the elements in ascending order of their atomic weights, and here a pattern emerged that at certain intervals of elements their properties periodically repeat. True, exceptions had to be made: some elements were swapped and not corresponded to the increase in atomic masses (for example, tellurium and iodine), but they corresponded to the properties of the elements.Further development of the atomic and molecular theory justified such shifts and showed the validity of this arrangement.You can read more about this in the article "What is the discovery of Mendeleev"

As we can see, the layout of the elements in this version is not at all the same as we see in the modern form. Firstly, groups and periods are reversed: groups horizontally, periods vertically, and secondly, there are a bit too many groups in it - nineteen, instead of eighteen accepted today.

However, just a year later, in 1870, Mendeleev formed a new version of the table, which is already more recognizable to us: similar elements are lined up vertically, forming groups, and 6 periods are arranged horizontally. It is especially noteworthy that in both the first and second versions of the table one can see significant achievements that his predecessors did not have: the table carefully left places for elements that, according to Mendeleev, had yet to be discovered. The corresponding vacancies are indicated by him with a question mark and you can see them in the picture above. Subsequently, the corresponding elements were indeed discovered: Galium, Germanium, Scandium. Thus, Dmitry Ivanovich not only systematized the elements into groups and periods, but also predicted the discovery of new, not yet known, elements.

Later, after resolving many of the topical mysteries of chemistry of that time - the discovery of new elements, the isolation of a group of noble gases together with the participation of William Ramsay, the establishment of the fact that Didymium is not an independent element at all, but is a mixture of two others - more and more new and new versions of the table, sometimes even having a non-table view at all. But we will not give them all here, but we will give only the final version, which was formed during the life of the great scientist.

Transition from atomic weights to nuclear charge.

Unfortunately, Dmitry Ivanovich did not live to see the planetary theory of the structure of the atom and did not see the triumph of Rutherford's experiments, although it was with his discoveries that a new era began in the development of the periodic law and the whole periodic system. Let me remind you that from the experiments conducted by Ernest Rutherford, it followed that the atoms of the elements consist of a positively charged atomic nucleus and negatively charged electrons revolving around the nucleus. After determining the charges of the atomic nuclei of all elements known at that time, it turned out that in the periodic system they are located in accordance with the charge of the nucleus. And the periodic law has acquired a new meaning, now it began to sound like this:

"Properties of chemical elements, as well as the forms and properties formed by them simple substances and compounds are in a periodic dependence on the magnitude of the charges of the nuclei of their atoms "

Now it became clear why some of the lighter elements were put by Mendeleev behind their heavier predecessors - the whole point is that this is how they stand in the order of the charges of their nucleus. For example, tellurium is heavier than iodine, but it is earlier in the table, because the charge of the nucleus of its atom and the number of electrons is 52, while iodine has 53. You can look at the table and see for yourself.

After the discovery of the structure of the atom and the atomic nucleus, the periodic system underwent several more changes, until, finally, it reached the form already familiar to us from school, the short-period version of the periodic table.

In this table, we already know everything: 7 periods, 10 series, side and main subgroups. Also, with the time of the discovery of new elements and filling the table with them, elements like Actinium and Lanthanum had to be placed in separate rows, all of them were respectively named Actinides and Lanthanides. This version of the system existed for a very long time - in the world scientific community almost until the end of the 80s, the beginning of the 90s, and in our country even longer - until the 10s of this century.

A modern version of the periodic table.

However, the option that many of us went through at school actually turns out to be very confusing, and the confusion is expressed in the division of subgroups into main and secondary ones, and remembering the logic of displaying the properties of elements becomes quite difficult. Of course, despite this, many studied it, became doctors chemical sciences, but still in modern times it has been replaced by a new option - a long-period one. I note that this particular option is approved by IUPAC (International Union of Pure and Applied Chemistry). Let's take a look at it.

The eight groups were replaced by eighteen, among which there is no longer any division into main and secondary, and all groups are dictated by the arrangement of electrons in the atomic shell. At the same time, they got rid of two-row and single-row periods, now all periods contain only one row. How convenient is this option? Now the periodicity of the properties of elements is viewed more clearly. The group number, in fact, indicates the number of electrons in the outer level, and therefore all the main subgroups of the old version are located in the first, second and thirteenth to eighteenth groups, and all the "former side" groups are located in the middle of the table. Thus, it is now clearly seen from the table that if this is the first group, then these are alkali metals and no copper or silver for you, and it is clear that all transit metals demonstrate well the similarity of their properties due to the filling of the d-sublevel, which affects to a lesser extent external properties, as well as lanthanides and actinides, exhibit similar properties due to only the f-sublevel being different. Thus, the whole table is divided into the following blocks: s-block, on which s-electrons are filled, d-block, p-block and f-block, with filling d, p, and f-electrons, respectively.

Unfortunately, in our country this option has been included in school textbooks only in the last 2-3 years, and even then not in all. And very wrong. What is it connected with? Well, firstly, with stagnant times in the dashing 90s, when there was no development at all in the country, not to mention the education sector, namely in the 90s, the world chemical community switched to this option. Secondly, with a slight inertia and difficulty in perceiving everything new, because our teachers are accustomed to the old, short-term version of the table, despite the fact that it is much more difficult and less convenient when studying chemistry.

Expanded version of the periodic system.

But time does not stand still, science and technology too. The 118th element of the periodic system has already been discovered, which means that the next, eighth, period of the table will soon have to be discovered. In addition, a new energy sublevel will appear: the g-sublevel. The elements of its constituents will have to be moved down the table, like lanthanides or actinides, or this table will be expanded twice more, so that it will no longer fit on an A4 sheet. Here I will give only a link to Wikipedia (see Extended Periodic System) and will not repeat the description of this option once again. Anyone who is interested can follow the link and have a look.

In this version, neither f-elements (lanthanides and actinides) nor g-elements ("elements of the future" from Nos. 121-128) are listed separately, but make the table wider by 32 cells. Also, the element Helium is placed in the second group, since it is included in the s-block.

In general, it is unlikely that future chemists will use this option, most likely the periodic table will be replaced by one of the alternatives that are already put forward by brave scientists: the Benfey system, Stewart's "Chemical Galaxy" or another option. But this will be only after the achievement of the second island of stability of chemical elements and, most likely, it will be necessary more for clarity in nuclear physics than in chemistry, but for now, the good old Dmitry Ivanovich's periodic system will suffice.

Instruction

The periodic system is a multi-storey "house" in which the a large number of apartments. Each "tenant" or in his own apartment under a certain number, which is permanent. In addition, the element has a "surname" or name, such as oxygen, boron or nitrogen. In addition to these data, each "apartment" or information such as relative atomic mass is indicated, which may have exact or rounded values.

As in any house, there are "entrances", namely groups. Moreover, in groups, elements are located on the left and right, forming . Depending on which side there are more of them, that side is called the main one. The other subgroup, respectively, will be secondary. Also in the table there are "floors" or periods. Moreover, the periods can be both large (consist of two rows) and small (they have only one row).

According to the table, you can show the structure of the atom of an element, each of which has a positively charged nucleus, consisting of protons and neutrons, as well as negatively charged electrons rotating around it. The number of protons and electrons coincides numerically and is determined in the table by the ordinal number of the element. For example, the chemical element sulfur has #16, so it will have 16 protons and 16 electrons.

To determine the number of neutrons (neutral particles also located in the nucleus), subtract its serial number from the relative atomic mass of an element. For example, iron has a relative atomic mass of 56 and an atomic number of 26. Therefore, 56 - 26 = 30 protons in iron.

The electrons are located at different distances from the nucleus, forming electronic levels. To determine the number of electronic (or energy) levels, you need to look at the number of the period in which the element is located. For example, aluminum is in period 3, so it will have 3 levels.

By the group number (but only for the main subgroup), you can determine the highest valency. For example, the elements of the first group of the main subgroup (lithium, sodium, potassium, etc.) have a valency of 1. Accordingly, the elements of the second group (beryllium, magnesium, calcium, etc.) will have a valency of 2.

You can also analyze the properties of elements using the table. From left to right, the metallic properties decrease and the non-metallic properties increase. This is clearly seen in the example of period 2: it begins with an alkali metal sodium, then an alkaline earth metal magnesium, after it an amphoteric element aluminum, then non-metals silicon, phosphorus, sulfur, and the period ends gaseous substances- chlorine and argon. In the next period, a similar dependence is observed.

From top to bottom, a pattern is also observed - metallic properties are enhanced, and non-metallic ones are weakened. That is, for example, cesium is much more active than sodium.

If the periodic table seems difficult for you to understand, you are not alone! Although it can be difficult to understand its principles, knowing how to work with it will help in learning natural sciences. To get started, 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

The periodic table, or periodic table of chemical elements, begins at the top left and ends at the end of the last line of the table (bottom right). The elements in the table are arranged from left to right in ascending order of their atomic number. The atomic number tells you how many protons are in one atom. In addition, as the atomic number increases, so does the atomic mass. 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 elements are arranged in groups, some table cells remain 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 on opposite ends because they belong to different groups.

2. Learn about groups that include elements with similar physical and chemical properties. The elements of each group are located in the corresponding vertical column. As a rule, 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 in the outer shell.

   • Hydrogen can be classified as a group alkali metals, and to the halogen group. 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 given in Roman (eg IA) or Arabic (eg 1A or 1) numerals.
   • When moving along the column from top to bottom, they say that you are "browsing the group".

3. Find out why there are empty cells in the table. Elements are ordered not only according to their atomic number, but also according to groups (elements of the same group have similar physical and chemical properties). This makes it easier to understand how an 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 found only from atomic number 21.
   • Elements with atomic numbers from 57 to 102 belong to the rare earth elements, and they are usually placed in a separate 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 electrons are located in atoms. The number of orbitals corresponds to the period number. 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.
   • As you move along a line from left to right, you are said to be "scanning through 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 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 an abbreviated name for an element that is the same in most languages. When experimenting and working with chemical equations element symbols are commonly used, so it's good to remember them.

      • Typically, element symbols are shorthand for their Latin name, although for some, especially recently discovered elements, they are derived from the 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 given in the table. This "name" of the element is used in normal texts. For example, "helium" and "carbon" are the names of the elements. Usually, although not always, full names elements are listed below 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 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, another chemical element would have turned out!

      • The atomic number of an element can also be used to 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 electric charge. If there are more protons in the ion, then 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, which is indicated by a minus sign.
      • The plus and minus signs are omitted if the atom is not an ion.