Chemical elements.

Achievements and prospects

The definition that D.I. Mendeleev gave to chemical science still remains correct and accurate: “Chemistry is the study of elements and chemical compounds.” Chemical elements are the foundation of all chemistry, since all known today are composed of them. chemical compounds(currently there are more than 14 million), as well as all those that will someday be received.

Many quite rightly perceive the main part of the periodic table as a list of elementary “bricks” from which objects in the surrounding world are built. However, chemical elements should not be considered only as “building materials” for constructing molecules, since in their pure form they have merits no less than millions of compounds obtained from them, and are extremely widely used in modern world(see more about this: Chemical elements in everyday life. “Chemistry”, 1998, No. 42).

Respecting strict terminology, we note that a chemical element is a Latin symbol in the periodic table or a specific atom, but subsequent research can be obtained and carried out not with a chemical element, but only with a so-called simple substance consisting of atoms of the same type. In English-language literature it is simpler: both are called in one word - element. Therefore, we will further use the Russian analogue of this word in the broad sense.

Summing up the results of the century, let us first of all consider how the periodic table was filled with new elements in the current century. By the end of the previous century, D.I. Mendeleev’s table contained about 80 elements. Beginning of the 20th century was marked by the award Nobel Prize W. Ramsay for the discovery of inert gases (1904); however, such an event was not always celebrated so solemnly. The production of only two more elements - radium and polonium - was noted in the same way (M. Sklodowska-Curie, Nobel Prize 1911).

In 1927, rhenium was obtained. This was a unique milestone in the history of the discovery of new elements, since rhenium was the last stable chemical element found in nature. Then everything became much more complicated, since all subsequent elements could be obtained exclusively using nuclear reactions.

It took quite a lot of time to fill the four empty cells in the middle of the table to uranium (see about this: Errors and misconceptions in the history of chemistry. "Chemistry", 1999, No. 8). Technetium - element No. 43 - was obtained in 1937 by prolonged irradiation of a molybdenum plate with heavy hydrogen (deuterium) nuclei. Element No. 87 - francium - was discovered in 1939 in the radioactive decay products of natural actinium. Element number 85 - astatine - was obtained in 1940 by bombarding bismuth with helium nuclei. Element No. 61, promethium, was isolated in 1945 from the fission products of uranium. Then, with the help of nuclear fusion reactions, the 7th period of the table began to be gradually filled with elements following uranium. The last chemical element to receive a name was No. 109. Elements from No. 110 onwards are designated only by atomic numbers.

Now we can already say that the twentieth century is ending no less solemnly than it began. In December 1998, a new element, No. 114, was obtained in Dubna by irradiating a plutonium isotope with a beam of accelerated calcium ions. If we sum up the number of protons of two interacting nuclei - plutonium and calcium, we get 94 + 20 = 114. This corresponds to element number 114. However, the resulting nucleus, whose mass is 244 + 48 = 292, turned out to be unstable. It emits three neutrons and forms an isotope. Preliminary calculations showed that element No. 114, as well as the so far unattainable elements No. 126 and No. 164, should fall into the so-called islands of stability. Regarding element No. 114, this was confirmed. Its lifetime is more than 0.5 minutes, which is a very large value for such a superheavy atom. In 1999, element No. 118 was obtained at the Berkeley Laboratory (USA) by bombarding lead with krypton ions. Its lifetime is milliseconds. When it decays, it forms a new unstable element No. 116, which quickly turns into the more stable element No. 114.

So, today the periodic table ends with the 118th element. Experiments on the synthesis of new elements are extremely labor-intensive and quite lengthy. The fact is that, passing through the electron shells of atoms, projectile nuclei are slowed down and lose energy. In addition, the nucleus formed during fusion most often disintegrates into two lighter nuclei. Only in rare cases does it emit several neutrons (as, for example, when obtaining element No. 114) and form the desired heavy nucleus. Despite the difficulties, experiments aimed at synthesizing new elements continue.

Considering all the wealth of chemical elements accumulated to date, let's try to sum up the century. Let's conduct a kind of competition between all the chemical elements known today and try to determine which of them ended up in the 20th century. the most significant. In other words, we will note only those elements that most contributed to raising the level of civilization and the development of progress.

There are only two obvious leaders. The first one is Uranus, who created a completely new scientific discipline- nuclear physics and provided humanity with enormous reserves of energy. Many will likely find such leadership controversial. Uranus gave humanity the expectation of the grim consequences of the use of nuclear weapons, the accident of nuclear power plants (NPPs) and the problem of nuclear waste disposal.

All these fears are well founded, but let’s look at the issue in more detail.

As for the threat of the use of nuclear weapons, humanity constantly keeps this problem in its field of vision. All issues related to a complete ban on the production and use of such weapons will inevitably have to be resolved in the future. More complex and controversial is the issue of the use of nuclear energy for peaceful purposes. The Chernobyl disaster on April 26, 1986 led to the fact that all people’s hearts clench with anxiety at the words “radiation” and “exposure.” Confidence in nuclear power has been shaken around the world.

Shouldn't nuclear power plants be abandoned altogether? At first it seemed that this would happen. Many countries have begun to reconsider the need to build new stations. The referendums held showed that the majority of people believe that it is necessary to abandon the use of nuclear energy. However, a calm, sober analysis of everything that happened gradually led to different conclusions. In terms of accident rates, nuclear power plants are practically in last place among all modern sources that produce electricity in large quantities. Moreover, the number of deaths during the operation of nuclear power plants is somewhat lower than even in the food and textile industries.

This picture has not changed even when taking into account the consequences of the Chernobyl accident, the largest in the history of the development of nuclear energy. It happened primarily due to a gross violation of operating rules: the reactor contained an unacceptably small number of cadmium rods, which inhibited the reaction. In addition, the station did not have a protective cap to prevent the release of radioactive substances into the atmosphere. As a result, one of the worst options was realized. Nevertheless, the release of radioactive substances into the atmosphere did not exceed 3.5% of their total amount accumulated in the reactor. Of course, no one thinks that this can be reconciled. Nuclear power plant safety control systems were subsequently significantly revised. Major research and development efforts are currently aimed at increasing their accident-free operation. The reactor control must be reliably blocked both from criminal negligence and from possible malicious plans of terrorists. In addition, all newly constructed stations will be equipped with protective caps in order to exclude the possibility of radioactive substances entering into environment.

No one is going to downplay the dangers of nuclear reactors. However, whether we like it or not, all the accumulated experience in the development of civilization inevitably leads to a certain conclusion.

Never in the history of mankind has there been a case when it refused the achievements of progress only because they pose a certain danger. Explosions of steam boilers, railway and plane crashes, car accidents, and electric shocks have not led to humanity banning the use of these technical means. As a result, the intensity of work aimed at increasing their safety only increased. Bans took place only for various types of weapons. The same is the case with nuclear energy.

Will new nuclear power plants really be built? Yes, this is inevitable, since already more than a quarter of the electricity consumed by large cities (Moscow, St. Petersburg) is produced by nuclear power plants (in Western countries this figure is higher). Humanity will no longer be able to refuse this new type of energy. With reliably organized operation, nuclear power plants undoubtedly benefit in comparison with thermal stations that consume trains with hydrocarbon fuels and pollute the atmosphere with combustion products of coal and oil.
Hydroelectric power stations turn forests and arable lands into wetlands and disrupt the natural biorhythm of all life on a vast territory. Nuclear power plants are incomparably more convenient to operate. They can be located in places remote from coal deposits and without sources of hydroelectric power. Nuclear fuel is changed no more than once every six months. Fuel consumption can be assessed using the following indicator. The fission of 1 g of uranium isotopes releases the same amount of energy as the combustion of 2800 kg of hydrocarbon fuel. In other words, 1 kg of nuclear fuel replaces a train of coal.

At the same time, the world's uranium reserves contain millions of times more accumulated energy than the energy resources of existing gas, oil and coal reserves. Nuclear fuel will last for tens of thousands of years, given the ever-increasing need for energy sources. At the same time, hydrocarbon raw materials can be used much more efficiently for the synthesis of various organic products.

The question immediately arises of what to do with spent nuclear fuel waste. Many people have probably heard about the problems of burying such waste. Intensive scientific works to solve this problem (humanity usually catches on with some delay). One of the promising ways is the construction of nuclear reactors that reproduce fuel. In conventional nuclear reactors, the uranium isotope 238 U is a kind of ballast; the main reaction takes place with the participation of the isotope 235 U, which, by the way, is very small in natural uranium (less than 1%). However, low-active 238 U, being in a certain amount in a nuclear reactor, can capture part of the released neutrons, ultimately forming plutonium 239 Pu, which itself is a nuclear fuel, no less effective than 235 U.

The schemes of many nuclear transformations are simple and clear. Two indices are placed before the symbol of a chemical element. The upper one indicates the mass of the nucleus, i.e. the sum of protons and neutrons, the lower one indicates the number of protons, i.e. the positive charge of the nucleus. When writing a reaction equation, you must follow a simple rule - the total amounts of charges of protons and electrons in both sides of the equation must be equal. In addition, you should know one of the simple equations of nuclear chemistry - a neutron can decay into a proton and an electron: n 0 = p + + e – .

This is what the scheme for converting 238 U into 239 Pu looks like, thanks to which in the future it will be possible to use completely all reserves of natural uranium as fuel:

The first equation shows that a neutron is captured by a uranium nucleus and an extremely unstable uranium isotope is formed. The intermediate stage is the formation and decay of an unstable isotope of neptunium. In the second and third equations, a neutron is converted into a proton (which remains in the nucleus) and an electron, which is released in the form b - radiation. This is the traditional name for the flow of electrons emitted by a radioactive substance. As a result, a very stable isotope of plutonium is formed with a half-life of 24 thousand years, which can be used as nuclear fuel in the same reactors.

So, the problem of waste destruction is postponed for a while, but is not completely removed, however, it is, in principle, solvable.

When the reactor operates, the uranium nucleus decays to form radioactive isotopes of various elements with a lower mass. The main isotopes are cobalt 60 Co, strontium 90 Sr and cesium 137 Cs, promethium 147 Pm, technetium 99 Tc. Some of them have already found application, for example, in the treatment of tumors (cobalt guns), for pre-sowing stimulation of seeds, and even in forensics. Another area of ​​application is the sterilization of food and medical products, since the isotopes emitted by these b - and g - radiation does not lead to the appearance of radioactivity in the irradiated substance.

It is very attractive to be able to create based on such b -emitters are sources of electricity. Under the influence b -rays (i.e., the flow of electrons) in semiconductor substances such as silicon or germanium, a potential difference arises. This makes it possible to create, for example, based on the 147 Pm isotope, long-term sources of electric current that operate without recharging for many years.

A nuclear reactor can be used in the same way as a kind of reaction flask for the directed synthesis of isotopes of various elements, in addition to those formed during spontaneous decay. Various substances are placed in special capsules in a nuclear reactor, where they are intensively irradiated with neutrons, resulting in the formation of the corresponding isotopes. Obtained in this way g -active isotopes of thulium and ytterbium, as well as technetium isotopes formed in reactors, are used to create compact mobile installations that replace bulky X-ray machines. They can be used not only for diagnostics for medical purposes, but also for the needs of technology for the purpose of flaw detection of various structures and equipment.

Thus, radioactive waste contains quite noticeable reserves of unspent energy, and methods for its extraction will be further improved.

Summarize. Uranium occupies a prominent place among all other elements. Thanks to him, in the 20th century, a new scientific direction was created - nuclear physics - and a practically inexhaustible source of energy was discovered.

The second element that claims an exceptional role in the twentieth century is silicon. Proving its significance will not be difficult, since it is not associated with various dark fears, as is the case with uranium. In the second half of the century, bulky vacuum tube electronic computers were replaced by compact computers. The brain of the computer - the processor - is made of ultra-pure silicon crystal. The semiconductor properties of silicon made it possible to create miniature ultra-fast computing devices based on it, which formed the basis of all modern computers. Of course, computer production uses a lot of modern technologies and various substances, but since we are talking only about chemical elements, the exclusive role of silicon is obvious.

It is clear that we are now in the initial stage of a powerfully developing process - the hurricane proliferation of computers in literally all areas of human activity. This is not just a stage of technological progress. The observed result is more impressive than in the case of uranium, since there is not only the development of new technical means, but also a change in the lifestyle and way of thinking of mankind.

Computers are entering homes with determination and energy, captivating every family member, especially the younger generation. Before our eyes, to some extent, the process of restructuring human psychology is taking place. Computers are gradually replacing televisions and VCRs, since most people devote most of their free time to them. They open up amazing opportunities for creativity and leisure.

The capabilities of computers are unusually great, and therefore they become indispensable in the work of scientists, writers, poets, musicians, designers, chess players, and photographers. They have completely captivated fans of puzzles and strategy games, as well as those who want to learn foreign languages ​​and lovers of home cooking. World Information Network Internet literally doubled the capabilities of computers. Any information and reference sources, literary and encyclopedic publications have become available; but an exceptional opportunity arose for communication between people connected by common interests. As a result, most people feel a sense of affection for their computer comparable to the love they have for their pets.

It is impossible not to note the additional advantages of silicon based on its semiconductor properties. We mentioned one of them a little earlier. This is an opportunity to transform b - radiation into electricity. The second very valuable property is realized in solar panels - the ability to convert daylight into electrical energy. It is currently used in low-power devices such as calculators and to power spacecraft. In the near future, more powerful solar panels will find widespread use in everyday life.

Thus, silicon is partially invading even the energy sector, where uranium is the leader. So, the second winner of our competition is silicon, which opened the era of semiconductors and computer technology.

Competition between chemical elements can be arranged according to other parameters. Let's pose the question differently. Which one of chemical elements(let me remind you that we are not considering chemical compounds) is what humanity consumes most? Obviously, the one that produces the most. In order for the competition to be fair, let’s remove the difference effect atomic masses for elements, we will count them individually, that is, we will consider production volumes expressed in moles.

Below are, in ascending order, the average annual production (in moles) of some of the most commonly consumed elements (1980s levels):

W – 1.4 10 7 ; U – 2 10 8 ; Si – 2,8 10 8 ; Mo – 6 10 8 ; Ti – 6,3 10 8 ;
Mg – 8 10 9 ; Cu – 1,2 10 11 ; Al – 4,4 10 11 ; O – 1 10 12 ; Cl – 1,2 10 12 ;
S – 1,7 10 12 ; N – 5,1 10 12 ; Fe – 1,2 10 13 ; H – 3 10 13 ; C – 3,3 10 13 ,

Carbon took a dominant place thanks to coal and petroleum coke, consumed primarily by metallurgy. Diamonds and graphite make up only a small portion of all carbon produced and mined. Hydrogen quite naturally took second place, since its areas of application are extremely diverse: metallurgy, oil refining, chemical and glass production, as well as rocketry. Iron took an honorable third place in our competition, despite its rather high atomic mass.

Let me remind you that we are comparing the production of elements expressed in moles. If a comparison were made in mass terms, then iron would prove to be the undisputed leader. It has been known to mankind since ancient times, and its role in the development of progress has constantly increased. Figuratively speaking, the above-mentioned uranium and silicon can be compared to the new stars that flared up in the sky of the twentieth century, while iron is a reliable luminary that illuminates the entire path of civilization for many centuries. Iron is the core of all modern industry, and we can assume that this role will continue into the 21st century.

It is interesting to compare the series obtained above with the prevalence of elements in globe. Here are the eight most common elements (in order of increasing molar abundance): Na, Fe,H, Mg, Ca,Al, Si, O. Obviously, the pattern is different. Nature failed to impose its rules of the game on humanity. We consume most of all not what is available in maximum quantity, but what is dictated by the needs of progress.

The capabilities of chemical elements are far from being completely exhausted. I wonder which of them will be the most significant in the 21st century? It is hardly possible to predict this. Let us leave this issue to be decided and summed up by those who will celebrate 2101.

Let's return again to the periodic table - a wonderful catalog of chemical elements. Recently, it is more often depicted in the form of an expanded table. This configuration is incomparably more visual and convenient. The horizontal rows, called periods, became longer. In this version, there are no longer eight groups of elements, as before, but eighteen. The term “subgroups” disappears, only groups remain. All elements of the same type (they are marked with individual background coloring) are arranged compactly. Lanthanides and actinides, as before, are placed on separate lines.

Now let's try to look into the future. How will the periodic table be filled in further? The table shown above ends with the actinide lawrencium - No. 103. Let us consider the lower part of the table in more detail, introducing elements discovered in recent years.

The chemical properties of element No. 114, obtained in 1998, can be roughly predicted by its position in the periodic table. This is an intransition element located in the carbon group, and its properties should resemble the lead located above it. However, the chemical properties of the new element are not available for direct study - the element is fixed in the amount of several atoms and is short-lived.

The last element received today - No. 118 - has all seven electronic levels completely filled. Therefore, it is quite natural that it is in the group of inert gases - radon is located above it. Thus, the 7th period of the periodic table is completed. Spectacular finale of the century!

Throughout the twentieth century. Humanity has largely filled this seventh period, and it now extends from element No. 87 - France - to the newly synthesized element No. 118 (some elements in this period are not yet obtained, such as No. 113, 115 and 117).

The moment is coming, in a certain sense, solemn. From element No. 119 in the periodic table a new, 8th period will begin. This event will probably brighten the beginning of the next century. The scheme for the gradual completion of electronic shells is clear in general terms. Everything will be played according to an already known system: at a certain moment, f-elements corresponding to lanthanides, and then - analogues d-elements called transitional. The most interesting thing is that the elements of the 8th period will also begin to fill in a new one, which does not exist for all elements received today g-level. So, they will appear g-elements that have no analogues in the periodic table known to us today. There is reason to believe that they will precede f-elements.

A careful examination of the periodic table reveals a certain harmony in it, which is not immediately noticeable. It is thanks to this harmony that the system has some predictive power. Let's confirm this with several examples.

Let us pose the question: how many expected g-elements in the 8th period? A simple calculation allows you to find out. First, remember that electrons are located at certain levels. The number of possible levels for each element corresponds to the period number. Electronic levels are divided into sublevels called orbitals and designated by letters of the Latin alphabet s, p, d, f. Each new sublevel can appear only at a set moment when the atomic number reaches a certain value. Each sublevel (or, in other words, each orbital) can accommodate no more than two electrons. s- Each element can have only one orbital; it has either one or two electrons. R-There can be three orbitals, therefore, the maximum possible number of electrons in them is six. Why R-can there be only three orbitals? This is determined by the laws of quantum mechanics. In our conversation we will not focus on this. d-There can only be five orbitals, which means 10 electrons.

Group names of elements are given in accordance with the names of orbitals. Elements that are filled with electrons s- orbitals are called s-elements, if filled R-orbitals, then this R-elements, and so on. All this is clearly visible in the table, where for each type of element the corresponding background color is given. Thus, in each period of the table there are two s-elements, six each p- elements and ten d-elements. Check this simple pattern in the table ( d-elements appear for the first time only in the 4th period).

You probably noticed that the number of possible orbitals when going from s- To p- And d- orbitals has a simple pattern. This is a series of odd numbers: 1, 3, 5. How many possible numbers do you think there are? f-orbitals? Logic dictates seven. This is true, and they can accommodate a maximum of 14 electrons. Means, f-elements in one period can only be 14. This is exactly the number of lanthanides in the table. Actinoids too f-elements, and there are also 14 of them. Now the main question: how many can there be g-orbitals? Let us mentally extend the series of numbers: 1, 3, 5, 7. Therefore, g-orbitals are nine, and the number of possible g-elements – 18.

So, we have answered the question posed above. All this can be confirmed experimentally only in the distant future. What will be the number of the very first one? g- element? It is not yet possible to answer unequivocally, since the order in which the electronic levels are filled out may not be the same as in the upper part of the table. By analogy with the moment at which they appear f-elements, we can assume that this will be element No. 122.

Let's try to solve another issue. How many elements will there be in the 8th period? Since the addition of each electron corresponds to the appearance of a new element, you simply need to add up the maximum number of electrons in all orbitals from s before g: 2 + 6 + 10 + 14 + 18 = 50. For a long time this was assumed, but computer calculations show that in the 8th period there will be not 50, but 46 elements.

So, the 8th period, which, as we believe, will begin to fill in the 21st century, will extend from element No. 119 to No. 164. However, the discovery of a new element is an expected thing, but not always predictable, and therefore one must be prepared for the fact that element No. 119 will be received even before this article falls into the hands of the reader, which will add even greater solemnity to the moment of the advent of the new century.

A careful examination of the periodic table allows us to note another simple pattern. R-Elements first appear in the 2nd period, d-elements – in the 4th, f-elements – in the 6th. The result is a series of even numbers: 2, 4, 6. This pattern is determined by the rules for filling electron shells. Now you should understand why g- the elements will appear, as mentioned above, in the 8th period. A simple continuation of a series of even numbers! There are longer-range forecasts, but they are based on fairly complex calculations. For example, it is shown that in the 9th period there will be only 8 elements, as in the 2nd and 3rd, which is somewhat unexpected.

Very interesting, is there theoretically the last element of the periodic table? Modern calculations cannot yet answer this question, so it has not yet been resolved by science.

We have gone quite far in our forecasts, perhaps even into the 22nd century, which, however, is quite understandable. Trying to glance into the distant future is a completely natural desire for every person, especially at the moment when not only the century, but also the millennium is changing.

M.M.Levitsky

The latest additions to the periodic table are elements 113 and 115, which do not yet have their own names

Preparation of superheavy elements 113 and 115 1. A beam of calcium-48 ions (one shown) is accelerated to high speeds in a cyclotron and directed at an americium-243 target.

2. The target atom is americium-243. A nucleus made of protons and neutrons and a fuzzy electron cloud surrounding it

3. Accelerated calcium-48 ion and target atom (americium-243) immediately before collision

4. At the moment of the collision, a new superheavy element with serial number 115 is born, living for only about 0.09 seconds

5. Element 115 decays to element 113, which already lives for 1.2 seconds, and then along a chain of four alpha decays, lasting about 20 seconds

6. Spontaneous decay of the final link in the chain of alpha decays - element 105 (dubnium) into two other atoms

Scientists from two leading Russian and American nuclear research centers abandoned the arms race and, finally getting down to business, created two new elements. If any independent researchers confirm their results, the new elements will be dubbed "ununtrium" and "ununpentium". Chemists and physicists around the world, not paying attention to the ugly names, express delight at this achievement. Ken Moody, head of the American team based in Livermore national laboratory Lawrence, states: “New perspectives are thus opened for the periodic table.”

The periodic table to which Moody refers is a familiar poster that adorns the walls of any room where more than two chemists might meet at the same time. We all studied it in chemistry lessons in high school or junior years of university. This table was created to explain why various elements combine in one way and not another. Chemical elements are placed in it in strict accordance with atomic weight and chemical properties. The relative position of an element helps predict the relationships it will enter into with other elements. After the creation of the 113th and 115th total number known to science elements reached 116 (117, if we count the element with serial number 118, the synthesis of which was already observed in Dubna in 2002, but this discovery has not yet been officially confirmed. - PM editors).

The history of the creation of the periodic table began in 1863 (however, timid attempts were made before: in 1817, I.V. Döbereiner tried to combine elements into triads, and in 1843, L. Gmelin tried to expand this classification with tetrads and pentads. - Editorial " PM"), when the young French geologist Alexandre-Émile Beguyer de Chancourtois arranged all the elements known at that time in a chain in accordance with their atomic weight. Then he wrapped a ribbon with this list around the cylinder, and it turned out that chemically similar elements lined up in columns. Compared to the trial and error method - the only research approach, which was used by chemists of that time - this trick with a ribbon looked like a radical step forward, although it did not bring serious practical results.

Around the same time, the young English chemist John A.R. Newlands experimented in the same way with relative position elements. He noted that chemical groups are repeated every eight elements (like notes, which is why the author called his discovery the “law of octaves.” - PM editors). Believing that a great discovery was ahead, he proudly delivered a message to the British Chemical Society. Alas! The older, more conservative members of this society killed this idea, declaring it absurd, and for many years it was consigned to oblivion. (You shouldn’t blame conservative scientists too much - the “law of octaves” correctly predicted the properties of only the first seventeen elements. - PM editors).

Russian revival

In the 19th century, the exchange of scientific information was not as active as it is now. Therefore, it is not surprising that another five years passed before the revival of the forgotten idea. This time the insight came to the Russian chemist Dmitry Ivanovich Mendeleev and his German colleague Julius Lothar Meyer. Working independently of each other, they came up with the idea of ​​arranging the chemical elements in seven columns. The position of each element was determined by its chemical and physical properties. And here, as de Chancourtois and Newlands had previously noticed, the elements spontaneously combined into groups that could be called “chemical families.”

Mendeleev managed to look deeper into the meaning of what was happening. The result was a table with empty cells showing exactly where to look for elements that had not yet been discovered. This insight looks even more fantastic if we remember that at that time scientists had no idea about the structure of atoms.

Over the next century, the periodic table became more and more informative. From the simple diagram shown here, it has grown into a huge sheet, including specific gravity, magnetic properties, melting and boiling points. You can also add information about the building here. electron shell atom, as well as a list of atomic weights of isotopes, that is, heavier or lighter twins that many elements have.

Artificial elements

Perhaps the most important news that the first versions of the periodic table brought to chemists was an indication of where the yet undiscovered elements were located.

By the beginning of the 20th century, the suspicion began to grow among physicists that atoms are not structured at all as was commonly thought. Let's start with the fact that these are not monolithic balls at all, but rather volumetric structures stretched out in empty space. The clearer the ideas about the microworld became, the faster the empty cells were filled.

Direct indications of the gaps in the table radically accelerated the search for elements that had not yet been discovered, but were actually present in nature. But when an accurate theory was formed that adequately described the structure of the atomic nucleus, new approach to “completing” the periodic table. A technique was created and tested for creating “artificial” or “synthetic” elements by irradiating existing metals with streams of high-energy elementary particles.

If you add electrically uncharged neutrons to the nucleus, the element becomes heavier, but its chemical behavior does not change. But as the atomic weight increases, elements become more and more unstable and acquire the ability to spontaneously decay. When this happens, some free neutrons and other particles are scattered into the surrounding space, but most of the protons, neutrons and electrons remain in place and are rearranged into the form of lighter elements.

Newcomers to the table

This February, researchers from LLNL (Lawrence Livermore National Laboratory) and the Russian Joint Institute for Nuclear Research (JINR), using the above-described atomic bombardment technique, obtained two completely new elements.

The first of these, element 115, was obtained after americium was bombarded with a radioactive isotope of calcium. (For reference, americium, a metal not often found in everyday life, is used in smoke detectors of common fire alarms.) The bombardment produced four atoms of element 115, but after 90 milliseconds they disintegrated to create another newborn - element 113. These four atoms lived for almost one and a half seconds before lighter elements already known to science were formed from them. Artificial elements rarely have longevity - their inherent instability is a consequence of the excessive number of protons and neutrons in their nuclei.

And now - regarding their awkward names. Several years ago, the International Union of Pure and Applied Chemistry (IUPAC), headquartered in Research Triangle Park, N.C. decreed that new chemical elements should be given culturally neutral names. Such neutrality can be achieved if you use the Latin pronunciation of the serial number of this element in periodic table. Thus, the numbers 1, 1, 5 will be read “un, un, pent”, and the ending “ium” is added for reasons of linguistic coherence. (A neutral Latin name and corresponding three-letter symbol are given to the element temporarily until the International Union of Pure and Applied Chemistry approves its final name. The organization's guidelines, published in 2002, are that discoverers have priority in proposing a name for a new element , by tradition elements may be named after mythological events or characters (including celestial bodies), minerals, geographical regions, properties of the element, famous scientists. - Editorial Board "PM").

Even if these new elements do not live very long and are not found outside the walls of laboratories, their creation still means more than just filling empty cells and increasing the total number of elements known to science. “This discovery allows us to expand the applicability of fundamental principles of chemistry,” says Livermore Chief Moody, “and new advances in chemistry are leading to the creation of new materials and the development of new technologies.”

In a nuclear reactor with neutrons of several MeV, reactions can take place (n,p) and(n,a) . In this way, the four most important radioactive isotopes 14 C, 32 P, 35 S and 3 H are formed by the reactions:

14 N(n,p) 14 C; 32 S(n,p) 32 P; 35 Cl(n,a) 35 S; 6 Li(n,a) 3 H

In all of these cases, a radioactive isotope of another chemical element is formed from a target element, and thus it becomes possible to isolate these isotopes without carrier or with specified radioactivity.

To obtain radionuclides, in addition to nuclear reactors, other sources of bombarding particles and gamma quanta, the operation of which is based on the occurrence of various nuclear reactions, are widely used. Powerful streams of charged particles are obtained using accelerators(electrostatic, linear and cyclotrons, etc.), in which charged particles are accelerated under the influence of constant or alternating fields. In electrostatic and linear accelerators, particles are accelerated by a single electric field; in cyclotrons, a magnetic field also acts simultaneously with the electric one.

Rice. Synchrophasotron

To produce high-energy neutrons, neutron generators are used, which use nuclear reactions under the influence of charged particles, most often deuterons. (d, n) or protons (p, n).

Using accelerators mainly receive radionuclides with different Z.

With boosters progress related recent years in the synthesis of new chemical elements. Thus, by irradiation in a cyclotron with alpha particles with an energy of 41 MeV and a beam density of 6 × 10 12 particles/s einsteinia the first 17 atoms were obtained mendelevium:

Subsequently, this gave impetus to the intensive development of the method of accelerating multiply charged ions. By bombarding uranium-238 in a cyclotron with carbon ions, californium was obtained:

U(C6+,6n)Cf

However, light projectiles - carbon or oxygen ions - made it possible to advance only to elements 104-10. Over time, to synthesize heavier nuclei, isotopes with serial numbers 106 and 107 were obtained by irradiating stable isotopes of lead and bismuth with chromium ions:

Pb(Cr,3n)Sg

209 83 B(Cr,2n)Bh

In 1985, the alpha-active element 108-hassium (Hs) was obtained in Dubna. irradiation with Cf neon-22:

Cf(Ne+4n)Hs

In the same year, in the laboratory of G. Seaborg, they synthesized 109 and 110 elements by irradiation of uranium-235 with argon nuclei 40.

The synthesis of further elements was carried out by bombarding U, curium-248, Es with Ca nuclei.

The synthesis of element 114 was carried out in 1999 in Dubna by fusion of calcium-48 and plutonium-244 nuclei. The new, superheavy nucleus cools, emitting 3-4 neutrons, and then decays by emitting alpha particles to element 110.

To synthesize element 116, a fusion reaction between curium-248 and calcium –48 was carried out. In 2000, the formation and decay of element 116 was recorded three times. Then, after about 0.05 s, the nucleus of element 116 decays to element 114, followed by a chain of alpha decays to element 110, which decays spontaneously.

The half-lives of the spontaneously decaying new elements synthesized were several microseconds. It would seem that continuing the synthesis of heavier elements becomes pointless, since their lifetime and yield are too short. At the same time, the discovered half-lives of these elements turned out to be much longer than expected. Therefore, it can be assumed that with a certain combination of protons and neutrons, stable nuclei with half-lives of many thousands of years should be obtained.

And so, obtaining isotopes that are not found in nature is a purely technical task, since theoretically the question is clear. You need to take a target, irradiate it with a stream of bombarding particles with the appropriate energy, and quickly isolate the desired isotope. However, choosing a suitable target and bombarding particles is not so easy.

Physicists from the Livermore National Laboratory in the United States in January 2016 reported progress in inertial controlled thermonuclear fusion. Using new technology, scientists were able to quadruple the efficiency of such installations. The research results were published in the journal Nature Physics, and were briefly reported by the Livermore National Laboratory and the University of California at San Diego. Lenta.ru talks about new achievements.

People have long been trying to find an alternative to hydrocarbon energy sources (coal, oil and gas). Burning fuel pollutes the environment. Its reserves are rapidly dwindling. The way out of the situation - dependence on water resources, as well as climate and weather - is the creation of thermonuclear power plants. To do this, it is necessary to achieve controllability of thermonuclear fusion reactions, which release the energy necessary for humans.

In thermonuclear reactors, heavy elements are synthesized from light ones (the formation of helium as a result of the fusion of deuterium and tritium). Conventional (nuclear) reactors, on the contrary, work on the decay of heavy nuclei into lighter ones. But for fusion it is necessary to heat the hydrogen plasma to thermonuclear temperatures (approximately the same as in the core of the Sun - one hundred million degrees Celsius or more) and keep it in an equilibrium state until a self-sustaining reaction occurs.

Work is being carried out in two promising areas. The first is associated with the possibility of confining heated plasma using magnetic field. Reactors of this kind include a tokamak (a toroidal chamber with magnetic coils) and a stellarator. In a tokamak, an electric current is passed through a plasma in the form of a toroidal cord; in a stellarator, a magnetic field is induced by external coils.

The ITER (International Thermonuclear Experimental Reactor) under construction in France is a tokamak, and the Wendelstein 7-X, launched in December 2015 in Germany, is a stellarator.

The second promising direction of controlled thermonuclear fusion is associated with lasers. Physicists propose using laser radiation to quickly heat and compress matter to the required temperatures and densities so that, being in the state of inertially confined plasma, it ensures the occurrence of a thermonuclear reaction.

Inertial controlled thermonuclear fusion involves the use of two main methods of igniting a pre-compressed target: impact - using a focused shock wave, and fast - implosion (explosion inward) of a spherical hydrogen layer inside the target. Each of them (in theory) should ensure optimal conversion of laser energy into pulsed energy and its subsequent transmission to a compressed spherical thermonuclear target.

The installation at the National Laser Fusion Facility in the United States uses the second approach, which involves separating the compression and heating phases. This, according to scientists, makes it possible to reduce the density of the fuel (or its mass) and provide higher gain factors. Heating is generated by a short pulse of a petawatt laser: an intense electron beam transfers its energy to the target. The experiments reported in the latest study were conducted in New York City at the OMEGA-60 facility at the University of Rochester Laser Energy Laboratory, which includes 54 lasers with a total energy of 18 kilojoules.

The system studied by scientists is structured as follows. The target is a plastic capsule with a thin deuterium-tritium layer applied to the inner wall. When the capsule is irradiated with lasers, it expands and forces the hydrogen located inside it to contract (during the first phase), which is heated (during the second phase) to plasma. Plasma from deuterium and tritium gives x-ray radiation and presses on the capsule. This scheme allows the system not to evaporate after being irradiated by a laser and ensures more uniform heating of the plasma.

In their experiments, scientists introduced copper into the plastic shell. When a laser beam is directed at the capsule, it releases fast electrons, which strike the copper indicators and cause them to emit X-rays. For the first time, scientists were able to present a technique for visualizing K-shell electrons, which allows them to track the transfer of energy by electrons inside the capsule and, as a result, more accurately calculate the parameters of the system. The importance of this work is as follows.

Achievement high degree Compression is hindered by fast electrons, the energy of which is converted into a large fraction of the radiation absorbed by the target. The free path of such particles coincides in order with the diameter of the target, as a result of which it overheats prematurely and does not have time to compress to the required densities. The study made it possible to look inside the target and track the processes occurring there, providing new information about the laser parameters necessary for optimal radiation of the target.

In addition to the United States, work related to inertial thermonuclear fusion is being carried out in Japan, France and Russia. In the city of Sarov, Nizhny Novgorod region, on the basis of the All-Russian Scientific Research Institute of Experimental Physics, in 2020 it is planned to put into operation the UFL-2M dual-purpose laser installation, which, among other tasks, should be used to study the conditions of ignition and combustion of thermonuclear fuel.

The efficiency of a thermonuclear reaction is defined as the ratio of the energy released in the fusion reaction to total energy spent on heating the system to the required temperatures. If this value is greater than one (one hundred percent), the laser fusion reactor can be considered successful. In experiments, physicists managed to transfer up to seven percent of the energy of laser radiation to fuel. This is four times the efficiency of quick ignition systems previously achieved. Computer modelling allows you to predict an increase in efficiency of up to 15 percent.

The published results raise the odds that the US Congress will extend funding for megajoule facilities such as the National Laser Fusion Facility in Livermore, which cost more than $4 billion to build and maintain. Despite the skepticism that accompanies fusion research, it is slowly but surely moving forward. In this area, scientists face not fundamental, but technological challenges that require international cooperation and adequate funding.

The International Union of Pure and Applied Chemistry (IUPAC) has announced which names it considers most appropriate for the four new elements of the periodic table. It is recommended to name one of them in honor of the Russian physicist, academician Yuri Oganesyan. Shortly before this, the KSh correspondent met with Yuri Tsolakovich and did a long interview with him. But IUPAC is asking scientists not to comment until November 8, when the new names will be officially announced. Regardless of whose name appears in the periodic table, we can state: Russia has become one of the leaders in the transuranium race, which has been going on for more than half a century.

Yuri Oganesyan. Specialist in the field of nuclear physics, academician of the Russian Academy of Sciences, scientific director of the Laboratory of Nuclear Reactions at JINR, head of the Department of Nuclear Physics at the University of Dubna. As a student of Georgy Flerov, he participated in the synthesis of rutherfordium, dubnium, seaborgium, bohrium, etc. Among the world-class discoveries is the so-called cold fusion nuclei, which turned out to be an extremely useful tool for creating new elements.

In the lower lines of the periodic table you can easily find uranium, its atomic number is 92. All subsequent elements do not exist in nature now and were discovered as a result of very complex experiments.
American physicists Glenn Seaborg and Edwin MacMillan were the first to create a new element. This is how plutonium was born in 1940. Later, together with other scientists, Seaborg synthesized americium, curium, berkelium... The very fact of man-made expansion of the periodic table is in some sense comparable to a flight into space.

The leading countries of the world have entered the race to create super-heavy nuclei (if desired, an analogy could be drawn with the lunar race, but here our country is more likely to win). In the USSR, the first transuranium element was synthesized in 1964 by scientists from the Joint Institute for Nuclear Research (JINR) in Dubna, Moscow Region. It was the 104th element - called rutherfordium. The project was led by one of the founders of JINR, Georgiy Flerov. His name is also included in the table: flerovium, 114. And the 105th element was called dubnium.

Yuri Oganesyan was a student of Flerov and participated in the synthesis of rutherfordium, and then dubnium, seaborgium, bohrium... The successes of our physicists made Russia a leader in the transuranium race along with the USA, Germany, Japan (and perhaps the first among equals).

The new elements in question - 113, 115, 117, 118 - were synthesized in 2002–2009 at JINR at the U-400 cyclotron. In accelerators of this type, beams of heavy charged particles - protons and ions - are accelerated using high-frequency electric field, in order to then collide them with each other or with a target and study the products of their decay.

All experiments were carried out by international collaborations almost simultaneously in different countries. For example, scientists from the Japanese RIKEN Institute synthesized the 113th element independently of the others. As a result, the opening priority was given to them.

A new chemical element is first given a temporary name, derived from the Latin numeral. For example, ununoctium is "one hundred and eighteenth". Then the scientific team - the author of the discovery - sends its proposals to IUPAC. The commission is considering the arguments for and against. In particular, she recommends adhering to the following rules: “Newly discovered elements may be named: (a) after a mythological character or concept (including an astronomical object); (b) by the name of a mineral or similar substance; (c) by the name of a locality or geographic area; (d) in accordance with the properties of the element or (e) by the name of the scientist..."

Names should be easy to pronounce in most languages. known languages and contain information that allows an element to be unambiguously classified. For example, all transurans have two-letter symbols and end in “-iy” if they are metals: rutherfordium, dubnium, seaborgium, bohrium...

Whether the two new elements (115 and 118) will receive “Russian” names will become clear in November. But there are still many experiments ahead, because according to the hypothesis of islands of stability, there are heavier elements that can exist for a relatively long time. They are even trying to find such elements in nature, but it would be more accurate if Oganesyan synthesizes them at an accelerator.

Dossier on new elements

Serial number: 113

How and by whom it was discovered: a target of americium-243 was bombarded with calcium-48 ions and ununpentium isotopes were obtained, which decayed into isotopes of element 113. Synthesized in 2003.

Opening priority: Institute of Physical and Chemical Research (RIKEN), Japan.

Current name: ununtry.

Intended properties: heavy fusible metal.

Suggested name: nihonium (Nh). This element was the first to be discovered in Asia in general and Japan in particular. “Nihonii” is one of two options for the country’s self-name. "Nihon" translates to "land of the rising sun."

Serial number: 115

How and by whom it was discovered: americium-243 target was bombarded with calcium-48 ions. Synthesized in 2003. Priority in discovery: collaboration consisting of JINR (Russia), Livermore National Laboratory (USA) and Oak Ridge National Laboratory (USA).

Current name: ununpentium.

Intended properties: metal similar to bismuth.

Suggested name: moscovium (Moscovium, Mc). IUPAC approved the name “Moscow” in honor of the Moscow region, where Dubna and JINR are located. Thus, this Russian city can leave its mark on the periodic table for the second time: dubnium has long been officially called the 105th element.

Serial number: 117

How and by whom it was discovered: a berkelium-249 target was bombarded with calcium-48 ions. Synthesized in 2009. Priority for discovery: JINR, Livermore, Oak Ridge.

Current name: ununseptium.

Intended properties: formally refers to halogens like iodine. The actual properties have not yet been determined. Most likely, it combines the characteristics of a metal and a non-metal.

Suggested name: Tennessine (Ts). In recognition of the contributions of the State of Tennessee, USA, including Oak Ridge National Laboratory, Vanderbilt University, and the University of Tennessee, to the synthesis of transuraniums.

Serial number: 118

How and by whom it was discovered: a californium-249 target was bombarded with calcium-48. Synthesized in 2002. Priority in discovery: JINR, Livermore.

Current name: ununoctium.

Intended properties: By chemical characteristics refers to inert gases.

Suggested name: oganesson (Oganesson, Og). In honor of scientific supervisor Laboratory of Nuclear Reactions of JINR Yuri Oganesyan, who made a great contribution to the study of superheavy elements. Public discussion of possible names will last until November 8, after which the commission will make a final decision.

on "Schrodinger's Cat"