Artificially created elements. Why synthesize new chemical elements? Accessible about complex

14.1 Stages of element synthesis

In order to explain the prevalence in nature of various chemical elements and their isotopes, in 1948 Gamow proposed a model of the Hot Universe. According to this model, all chemical elements were formed at the time of the Big Bang. However, this claim was subsequently refuted. It has been proven that only light elements could be formed at the time of the Big Bang, while heavier ones arose in the processes of nucleosynthesis. These positions are formulated in the Big Bang model (see item 15).
According to the Big Bang model, the formation of chemical elements began with the initial nuclear fusion of light elements (H, D, 3 He, 4 He, 7 Li) 100 seconds after the Big Bang at a Universe temperature of 10 9 K.
The experimental basis of the model is the expansion of the Universe observed on the basis of redshift, the initial synthesis of elements and cosmic background radiation.
The big advantage of the Big Bang model is the prediction of the abundance of D, He and Li, which differ from each other by many orders of magnitude.
Experimental data on the abundance of elements in our Galaxy showed that hydrogen atoms are 92%, helium - 8%, and heavier nuclei - 1 atom per 1000, which is consistent with the predictions of the Big Bang model.

14.2 Nuclear fusion - synthesis of light elements (H, D, 3 He, 4 He, 7 Li) in the early Universe.

• The abundance of 4 He or its relative fraction in the mass of the Universe is Y = 0.23 ±0.02. At least half of the helium produced in the Big Bang is contained in intergalactic space.
• The original deuterium exists only inside the Stars and quickly turns into 3 He.
  Observational data yield the following limits on the abundance of deuterium and He with respect to hydrogen:

10 -5 ≤ D/H ≤ 2 10 -4 and
1.2 10 -5 ≤ 3 He/H ≤ 1.5 10 -4 ,

moreover, the observed ratio D/H is only a fraction of ƒ from the initial value: D/H = ƒ(D/H) initial. Since deuterium quickly turns into 3 He, the following estimate for abundance is obtained:

[(D + 3 He)/H] initial ≤ 10 -4 .

• It is difficult to measure the abundance of 7 Li, but data on the study of stellar atmospheres and the dependence of the abundance of 7 Li on the effective temperature are used. It turns out that, starting from a temperature of 5.5·10 3 K, the amount of 7 Li remains constant. The best estimate of the average abundance 7 Li is:

7 Li/H = (1.6±0.1) 10 -10 .

• The abundance of heavier elements such as 9 Be, 10 V and 11 V is several orders of magnitude less. Thus, the prevalence is 9 Be/N< 2.5·10 -12 .

14.3 Synthesis of nuclei in Main Sequence stars at T< 108 K

Helium synthesis in Main Sequence stars in pp- and CN-cycles occurs at a temperature of T ~ 10 7 ÷7·10 7 K. Hydrogen is processed into helium. Nuclei of light elements arise: 2 H, 3 He, 7 Li, 7 Be, 8 Be, but there are few of them due to the fact that they subsequently enter into nuclear reactions, and the 8 Be nucleus almost instantly decays due to the short lifetime (~ 10 -16 s)

8 Be → 4 He + 4 He.

The process of synthesis seemed to have to stop, But nature has found a workaround.
When T > 7 10 7 K, helium "burns out", turning into carbon nuclei. There is a triple helium reaction - "Helium flash" - 3α → 12 C, but its cross section is very small and the process of formation of 12 C goes in two stages.
The fusion reaction of 8Be and 4He nuclei occurs with the formation of a 12C* carbon nucleus in an excited state, which is possible due to the presence of a level of 7.68 MeV in the carbon nucleus, i.e. reaction takes place:

8 Be + 4 He → 12 C* → 12 C + γ.

The existence of the energy level of the 12 C nucleus (7.68 MeV) helps to bypass the short lifetime of 8 Be. Due to the presence of this level, the nucleus 12 C occurs Breit-Wigner resonance. The 12 C nucleus passes to an excited level with energy ΔW = ΔM + ε,
where εM = (M 8Be − M 4He) − M 12C = 7.4 MeV, and ε is compensated by the kinetic energy.
This reaction was predicted by the astrophysicist Hoyle and then reproduced in the laboratory. Then the reactions begin:

12 C + 4 He → 16 0 + γ
16 0 + 4 He → 20 Ne + γ and so on up to A ~ 20.

So the required level of the 12 C nucleus made it possible to overcome the bottleneck in the thermonuclear fusion of elements.
The nucleus 16 O does not have such energy levels and the reaction of formation of 16 O is very slow

12 C + 4 He → 16 0 + γ.

These features of the course of reactions led to the most important consequences: thanks to them, it turned out the same number 12 C and 16 0 nuclei, which created favorable conditions for the formation of organic molecules, i.e. life.
A change in the level of 12 C by 5% would lead to a catastrophe - further synthesis of elements would stop. But since this did not happen, then nuclei are formed with A in the range

A = 25÷32

This leads to the values ​​A

All Fe, Co, Cr nuclei are formed by thermonuclear fusion.

It is possible to calculate the abundance of nuclei in the Universe based on the existence of these processes.
Information about the abundance of elements in nature is obtained from the spectral analysis of the Sun and Stars, as well as cosmic rays. On fig. 99 shows the intensity of the nuclei at different values ​​of A.

Rice. 99: The abundance of elements in the universe.

Hydrogen H is the most abundant element in the universe. Lithium Li, beryllium Be, and boron B are 4 orders of magnitude smaller than neighboring nuclei and 8 orders of magnitude smaller than H and He.
Li, Be, B are good fuels, they quickly burn out already at T ~ 10 7 K.
It is more difficult to explain why they still exist - most likely due to the process of fragmentation of heavier nuclei at the protostar stage.
IN cosmic rays Li, Be, B nuclei are much larger, which is also a consequence of the processes of fragmentation of heavier nuclei during their interaction with the interstellar medium.
12 C ÷ 16 O is the result of the Helium flash and the existence of a resonant level in 12 C and the absence of one in 16 O, the core of which is also doubly magic. 12 C - semi-magical core.
Thus, the maximum abundance of iron nuclei is 56 Fe, and then a sharp decline.
For A > 60, the synthesis is energetically unfavorable.

14.5 Formation of nuclei heavier than iron

The fraction of nuclei with A > 90 is small - 10 -10 of hydrogen nuclei. The processes of formation of nuclei are associated with side reactions occurring in stars. There are two such processes:
s (slow) − slow process,
r (rapid) is a fast process.
Both of these processes are associated with neutron capture those. it is necessary that conditions arise under which many neutrons are produced. Neutrons are produced in all combustion reactions.

13 C + 4 He → 16 0 + n - helium combustion,
12 C + 12 C → 23 Mg + n - carbon flash,
16 O + 16 O → 31 S + n − oxygen flash,
21 Ne + 4 He → 24 Mg + n − reaction with α-particles.

As a result, the neutron background accumulates and s- and r-processes can occur - neutron capture. When neutrons are captured, neutron-rich nuclei are formed, and then β-decay occurs. It turns them into heavier nuclei.

"THINKING OUT LOUD"

SCIENTIFIC NOVEL BASED ON SCIENTIFIC THEORY
UNIVERSE, NEUTRON PHYSICS AND NEUTRON CHEMISTRY

Valery Fedorovich Andrus

"Our task is to develop means of obtaining energy from reserves that are eternal and inexhaustible, to develop methods that do not use the consumption and consumption of any "material" carriers. Now we are absolutely sure that the realization of this idea is not far off. : the possibilities for the development of this concept lie precisely in using the clean energy of the surrounding space to operate engines anywhere on the planet ... "

(Tesla, 1897)

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Familiarize yourself with the basic concepts of neutron physics

NUCLEAR CHEMISTRY
SYNTHESIS OF ELEMENTS FROM THE POSITION OF NEUTRON PHYSICS

We talked about the artificial synthesis of elements and noted that these are not elements, but molecules and even alloys. At first glance, it may seem that this is a hypothesis and the situation is somehow different. To put an end to the "i" in these arguments, let's move on to nuclear chemistry.

“... The subject of nuclear chemistry is the reactions in which the transformation of elements occurs, i.e. change in the nuclei of their atoms.

The spontaneous decay of radioactive atoms, discussed above (we will return to it), is a nuclear reaction in which one nucleus is the initial one. Other reactions are also known in which a proton p, a deuteron (the nucleus of a deuterium atom 1 2 H) d, an alpha particle α, a neutron n or a photon γ (usually gamma rays) react with the nucleus. It was also possible to induce atomic transformations under the influence of fast electrons. Instead of α-particles (4 He nuclei), nuclei of the lighter helium isotope 3 He are sometimes used. Recently, accelerated nuclei of heavier elements up to neon have been increasingly used to bombard atomic nuclei.

The first nuclear reaction carried out in the laboratory was the reaction (Rutherford, 1919).

In this reaction, the nitrogen nucleus reacts with the helium nucleus, which has significant kinetic energy. As a result of the collision, two new nuclei are formed: Oxygen 17 O and Hydrogen 1 H. The 17 O nucleus is stable, so this reaction does not lead to the appearance of artificial radioactivity. In the majority of nuclear reactions, unstable isotopes are formed, which are then converted into stable isotopes by a series of radioactive transformations ... ”

For convenience and contrast, we will break the material into small pieces with explanations.

We do not have nuclei, but there is a six-pointed hedgehog of Nitrogen (14 N), which is bombarded by a hedgehog of Helium (4 He) consisting of a Hydrogen atom and six fives of neutrons along the “planes” of the cube.

Considering the final result of the reaction, we can safely say the following:

Hedgehog Nitrogen with six needles attached to each needle one five with a relative mass of 0.5, resulting in a hedgehog with a relative mass of 17 - Oxygen. We know that each new layer of fives is a new element.

Could the Nitrogen hedgehog get all six fives as a result of the destruction of one Helium hedgehog? Of course he couldn't. To obtain one Oxygen hedgehog, it was necessary to destroy many Helium hedgehogs, creating a neutron flux similar to gravitational one, with the same hedgehog growth pattern. This flow could not coincide with the gravitational one. As a result of the destruction of Helium, some cubes of Hydrogen remained intact. Excess neutrons are either free thermal carriers or radiation. The result of the reaction is the desired equation, which does not correspond to reality, since the excess neutrons of the flux are not taken into account. I hope you remember that the NF neutron is 9 times less in mass than the one with which the comparison is made in reactions. Let's continue.

“...According to Remy, nuclear reactions can be classified by analogy with ordinary chemical reactions.

In most artificial nuclear transformations, so-called displacement or substitution reactions occur. For example:

When writing nuclear reactions, they often use an abbreviated notation, in which the bombarding and knocking out particles are separated by a comma and enclosed in brackets, before which the symbol of the original is written, and after - the resulting atom. For example, the above reaction, which was first carried out by Rutherford, can be written as: 14 N( b,p) 17O.

In such a notation, we give more examples of nuclear substitution reactions that occur during bombardment with accelerated particles aluminum:

17AL(d,α) 25Mg, 27AL(d,p) 28AL, 27AL(d,n) 28Si, 27AL(p,α) 24Mg, 27AL(n,p) 27Mg.. .”

This passage deals with substitution reactions. From the point of view of the hedgehog model, there are no substitution reactions here. During the bombing hedgehog is coming or its absolutely normal growth, the same as in nature, or the loss of some fives in the needles. Knowing the material presented in the book, one can write complete series of such reactions without a single gap, and all of them have either already been obtained, or they can be obtained with 100% probability.

“... As a result of the addition reaction, the bombarding particle is captured by the nucleus, which, in turn, does not emit any other particle, and the energy released in this case is released in the form of γ-radiation, For example:

27\AL(n,γ) 28 AL, 7 Li(p,γ) 8 Be...”

This is the same process of normal growth of a hedgehog, as a result of which some neutrons were destroyed into fragments of γ-radiation.

“... Nuclear dissociation reactions (as well as reactions of thermal dissociation of molecules) are caused by the kinetic energy of colliding particles. For example: 79 Br(n,2n) 78 Br, 2 H( b,n and b) 1 H, 2 H(g, n) 1 H.

The last reaction is a photochemical reaction, i.e. caused by the action of electromagnetic radiation, nuclear dissociation.

A number of reversible reactions are currently known:

All reactions are the neutron interaction of a hedgehog of an object - a target, which is in an artificial flux or fragments of neutrons (γ), or neutrons or other hedgehogs, with a bombarding object. If the flow of ready-made neutrons is dense enough, then it will form fives, and the hedgehog will grow.

If the neutron flux is scattered or it needs to be obtained by first destroying the bombarding hedgehog, then the target hedgehog loses its fives.

The dissociation reaction is an intermediate state of flow between dense and diffuse.

We have already spoken about the reactions of artificial fusion and fission, but, as the Americans say, my word against yours may mean nothing, and then everyone will remain in his own opinion. However, the fission reaction, which will now be given, will fundamentally prove that the views of NF are correct.

Let us consider one of the reactions of fission of Uranium-235, used in nuclear power engineering, due to the absorption of a neutron.

110 54 Xe – β -110 55 Cs – β- 110 56 Ba – β–110 57 Za – β–110 58 Ce stable nucleus

235 92 U + 1 0 n → 5 1 0 n

91 36 Kg – β–91 37 Rb – β–91 38 Sr – β–91 39 – β–91 40 Zr stable nucleus

This reaction is a symbol of the triumph of NF. As it was previously stated that, as a result of synthesis, not elements, but molecules are obtained, and Uranium - 235 as a result of fission showed that it is an alloy of Ce and Zg. Even theoretically, it is impossible to get from one hedgehog by dividing two hedgehogs. Next come the usual transformations in the neutron flux according to NF (β-radiation).

This is the most striking example, which shows that we have not yet learned to distinguish between an element and a molecule, and even more so alloys. Hence the table of elements, especially after Technetium, is a table of molecules (alloys)!

What is a U=XeKg molecule? Why is she so resilient? Is it possible to get Uranus from other constituent elements?

Let's start with the last question. If Uranus is considered as a sum of relative masses, then, of course, it can be obtained from many variants of terms. However, for us they will all look the same, since we do not distinguish between them. When all kinds of research is done with him, he will always look like someone, more understandable to us, as it seems to us. Uranus has a gray metallic color, which suggests that the needles of its elements have many oppositely twisted fives and different hedgehogs with different spin of neutrons. The density of Uranus is close to the limit - 19.04 g / cm W - this is a sign of "air structures". The melting heat of Uranus is + 1130°С, and Xenon - 111.5°С and Krypton - 156.6°С. A molecule of two elements Xe and Kr cannot, in principle, have tmelt. + 1130°C, and even more so to create an “air structure”.

Now let's take a closer look at the end products of the reaction of Ce and Zr.

Cerium has a silvery white color, mp. = 804°C, g = 6.77 g/cm3.

Zirconium - silvery white color, mp. = 1852°С, g = 6.52 g/cm3

To obtain the characteristics of Uranus, the molecule must consist of Cerium and Zirconium, and the connection of the needles must create not a cubic lattice, but a rhombic one. Then a grayish color will appear, the “airiness of the lattice” and the densities tm will increase. approaches the average. The neutron twist of Zirconium will decrease, while that of Cerium will increase. This reaction can be written

U \u003d Ce Zr 4 - the original product (alloy Ce 20 Zr 80)

Uranium was obtained as a result of sedimentary bonds with four-needle joints with only the correct rhombic construction.

Let's summarize:

A fusion reaction is a combination of two or more elements into a molecule in a fleeting process that replaces the slow sedimentary process in nature, with their partial destruction.

A fission reaction is a transient rupture of a molecule into two or more elements with their partial destruction. The number of finite elements is equal to the number of initial ones in the molecule.

As you can see, the table of elements will still have to suffer.

Back to nuclear reaction

Here Carbon is obtained as a result of an attack by Bohr's α-packets. Boron also sits in the Beryllium-liquid cage and has three fives in needles. They are both clearly in the wrong place. We look at the table D.I. Mendeleev and see the density in the range of 1.5 ÷ 2.5 g / cm 3 for 11 elements (Be, B, C, Mg, Si, P, S, Cl, Ar, Ca, Cs).

Cesium (Cs) is the 55th element with the length of the needles according to the relative mass equal to 44 fives at a density g = 1.959 g/cm 3 . According to neutron logic, it should stand in front of Boron and Carbon and have a needle length of two fives and be weightless in the earth's atmosphere, and in practice all three elements do not have this.

In an analysis of carbides, which will not be given, Carbon lies between Zirconium (Zr) and Niobium (Nb). The last one (Nb) according to the table of transformations sits in the last cell of Zirconium (Zr).

The length of the Carbon needles should be around 30 fives. Only in this case, the diamond can receive the channels pierced by the ropes of Light as a laser beam with the thickness of the last up to 30 threads in one rope.

The first way to get small diamonds suitable for diamonds is as follows:

Finely dispersed graphite powder is poured into a vessel with water, which is allowed to settle quietly.

After all the powder has settled to the bottom, the water is removed in the most calm way.

The pressed tile must be heated by HDTV (high frequency currents) in a compressed state to a maximum temperature, preferably up to 3000 ° C and maintained.

Place a hot tile under the laser, which should pass its beam line by line, like a frame scan on a TV.

A slow and gentle process will produce tile-thick crystals. At the same time, transparency can also be controlled by repeating the passage of the laser beam.

To obtain large and very large diamonds, the entire process at the finish line must be carried out even more slowly. We repeat the first four technological points. The shape of graphite must match the shape of the future diamond.

Hot graphite is placed in a deep-freeze chamber in an adjustable shaking mechanism and the temperature in the chamber is sharply reduced to a value close to -260 ° C. Thus, achieving a shock heat flow from the center of the workpiece to the surface, which will gently destroy some of the joints. After complete cooling, we perform soft shaking until the workpiece is completely transparent. As a result of shaking, the diamond structure, which is completely interconnected, will receive the smallest vibrations. Graphite not connected vertically will have a free swing, which will lead to breaking off of needles and opening channels for the ropes of Light.

If you ask scientists, which of the discoveries of the XX century. most important, then hardly anyone will forget to name the artificial synthesis of chemical elements. Behind short term- less than 40 years - list known chemical elements increased by 18 names. And all 18 were synthesized, prepared artificially.

The word "synthesis" usually means the process of obtaining from a simple complex. For example, the interaction of sulfur with oxygen is the chemical synthesis of sulfur dioxide SO 2 from the elements.

Synthesis of elements can be understood in this way: artificial production of an element with a lower nuclear charge, a lower serial number of an element with a higher serial number from an element with a lower nuclear charge. And the process of obtaining is called a nuclear reaction. Its equation is written in the same way as the equation of an ordinary chemical reaction. The reactants are on the left and the products are on the right. The reactants in a nuclear reaction are the target and the bombarding particle.

The target can be any element of the periodic system (in free form or in the form of a chemical compound).

The role of bombarding particles is played by α-particles, neutrons, protons, deuterons (nuclei of the heavy isotope of hydrogen), as well as the so-called multiply charged heavy ions of various elements - boron, carbon, nitrogen, oxygen, neon, argon and other elements of the periodic system.

For a nuclear reaction to occur, the bombarding particle must collide with the nucleus of the target atom. If the particle has a sufficiently high energy, then it can penetrate so deeply into the nucleus that it merges with it. Since all the particles listed above, except for the neutron, carry positive charges, then, merging with the nucleus, they increase its charge. And changing the value of Z means the transformation of elements: the synthesis of an element with a new value of the nuclear charge.

In order to find a way to accelerate the bombarding particles, to give them high energy sufficient for their fusion with nuclei, a special particle accelerator, the cyclotron, was invented and constructed. Then they built a special factory of new elements - a nuclear reactor. Its direct purpose is to generate nuclear energy. But since there are always intense neutron fluxes in it, they are easy to use for the purposes of artificial synthesis. The neutron has no charge, and therefore it is not necessary (and impossible) to accelerate. On the contrary, slow neutrons turn out to be more useful than fast ones.

Chemists had to rack their brains and show genuine miracles of ingenuity in order to develop ways to separate negligible amounts of new elements from the target substance. Learn to study the properties of new elements when only a few of their atoms were available...

Through the work of hundreds and thousands of scientists, eighteen new cells were filled in the periodic table.

Four are within its old boundaries: between hydrogen and uranium.

Fourteen - for uranium.

Here's how it all happened...

Technetium, promethium, astatine, francium... Four places in the periodic table remained empty for a long time. These were cells No. 43, 61, 85 and 87. Of the four elements that were supposed to take these places, three were predicted by Mendeleev: ekamanganese - 43, ekaiod - 85 and ekacesium - 87. The fourth - No. 61 - should have belonged to rare earth elements .

These four elements were elusive. The efforts of scientists aimed at searching for them in nature remained unsuccessful. With the help of the periodic law, all other places in the periodic table have long been filled - from hydrogen to uranium.

Not once in scientific journals there were reports of the discovery of these four elements. Ecamarganese was "discovered" in Japan, where it was given the name "nipponium", in Germany it was called "masurium". Element No. 61 was "opened" in different countries at least thrice, he received the names "Illinium", "Florence", "Onium cycle". Ekaiod was also found in nature more than once. He was given the names "Alabamy", "Helvetius". Ekacesium, in turn, received the names "Virginia", "Moldavia". Some of these names ended up in various reference books and even found their way into school textbooks. But all these discoveries were not confirmed: each time an exact check showed that a mistake had been made, and random insignificant impurities were mistaken for a new element.

A long and difficult search finally led to the discovery in nature of one of the elusive elements. It turned out that ecacesium, which should occupy the 87th place in the periodic table, occurs in the decay chain of the natural radioactive isotope uranium-235. It is a short lived radioactive element.

Element number 87 deserves to be told in more detail.

Now in any encyclopedia, in any textbook on chemistry we read: francium (serial number 87) was discovered in 1939 by the French scientist Marguerite Perey. By the way, this is the third case when the honor of discovering a new element belongs to a woman (previously Marie Curie discovered polonium and radium, Ida Noddack discovered rhenium).

How did Perey manage to capture the elusive element? Let's go back many years. In 1914, three Austrian radiochemists - S. Meyer, W. Hess and F. Panet - began to study the radioactive decay of the actinium isotope with a mass number of 227. It was known that it belongs to the actinouranium family and emits β-particles; hence its decay product is thorium. However, scientists had a vague suspicion that actinium-227, in rare cases, also emits α-particles. In other words, one of the examples of a radioactive fork is observed here. It is easy to imagine that in the course of such a transformation, an isotope of element No. 87 should be formed. Meyer and his colleagues actually observed α-particles. Further studies were required, but they were interrupted by the First World War.

Marguerite Perey followed the same path. But she had at her disposal more sensitive instruments, new, improved methods of analysis. That is why she was successful.

Francium is one of the artificially synthesized elements. But still, the element was first discovered in nature. It is an isotope of francium-223. Its half-life is only 22 minutes. It becomes clear why there is so little France on Earth. Firstly, because of its fragility, it does not have time to concentrate in any noticeable quantities, and secondly, the process of its formation itself is characterized by a low probability: only 1.2% of actinium-227 nuclei decays with the emission of α-particles.

In this regard, francium is more profitable to prepare artificially. Already received 20 isotopes of francium, and the longest-lived of them - francium-223. Working with absolutely negligible amounts of francium salts, chemists were able to prove that in its properties it is extremely similar: to cesium.

Elements #43, 61 and 85 remained elusive. In nature, they could not be found in any way, although scientists already possessed a powerful method that unmistakably points the way for the search for new elements - the periodic law. Thanks to this law, all the chemical properties of an unknown element were known to scientists in advance. So why were the searches for these three elements in nature unsuccessful?

Studying the properties of atomic nuclei, physicists came to the conclusion that elements with atomic numbers 43, 61, 85 and 87 cannot have stable isotopes. They can only be radioactive, with short half-lives, and should disappear quickly. Therefore, all these elements were created by man artificially. The paths for creating new elements were indicated by the periodic law. Let's try with its help to outline the route for the synthesis of ecamarganese. This element number 43 was the first artificially created.

The chemical properties of an element are determined by its electron shell, and it depends on the charge of the atomic nucleus. There should be 43 positive charges in the nucleus of element 43, and 43 electrons should revolve around the nucleus. How can you create an element with 43 charges in the atomic nucleus? How can one prove that such an element has been created?

Let us consider carefully which elements in the periodic system are located near the empty space intended for element No. 43. It is located almost in the middle of the fifth period. In the corresponding places in the fourth period is manganese, and in the sixth - rhenium. Therefore, the chemical properties of the 43rd element should be similar to those of manganese and rhenium. No wonder D. I. Mendeleev, who predicted this element, called it ecamarganese. To the left of cell 43 is molybdenum, which occupies cell 42, to the right, in cell 44, ruthenium.

Therefore, in order to create element number 43, it is necessary to increase the number of charges in the nucleus of an atom, which has 42 charges, by one more elementary charge. Therefore, for the synthesis of a new element No. 43, molybdenum must be taken as a feedstock. It has 42 charges in the core. The lightest element, hydrogen, has one positive charge. So, it can be expected that element No. 43 can be obtained as a result of a nuclear reaction between molybdenum and hydrogen.

The properties of element No. 43 must be similar to those of manganese and rhenium, and in order to detect and prove the formation of this element, one must use chemical reactions similar to those by which chemists determine the presence of small amounts of manganese and rhenium. This is how the periodic table makes it possible to chart the way for the creation of an artificial element.

In exactly the same way that we have just outlined, the first artificial chemical element was created in 1937. He received a significant name - technetium - the first element made by technical, artificial means. This is how technetium was synthesized. The plate of molybdenum was subjected to intense bombardment by nuclei of the heavy isotope of hydrogen - deuterium, which were dispersed in the cyclotron to great speed.

The nuclei of heavy hydrogen, which received very high energy, penetrated into the nuclei of molybdenum. After irradiation in the cyclotron, the molybdenum plate was dissolved in acid. An insignificant amount of a new radioactive substance was isolated from the solution using the same reactions that are necessary for the analytical determination of manganese (analogue of element No. 43). This was the new element, technetium. Soon its chemical properties were studied in detail. They correspond exactly to the position of the element in the periodic table.

Now technetium has become quite affordable: it is formed in fairly large quantities in nuclear reactors. Technetium has been well studied and is already being used in practice. Technetium is used to study the process of corrosion of metals.

The method by which the 61st element was created is very similar to the method by which technetium is obtained. Element #61 must be a rare earth element: the 61st cell is between neodymium (#60) and samarium (#62). The new element was first obtained in 1938 in a cyclotron by bombarding neodymium with deuterium nuclei. Element 61 was chemically isolated only in 1945 from fragmentation elements formed in a nuclear reactor as a result of uranium fission.

The element received the symbolic name promethium. This name was given to him for a reason. The ancient Greek myth tells that the titan Prometheus stole fire from the sky and gave it to people. For this he was punished by the gods: he was chained to a rock, and a huge eagle tormented him every day. The name "promethium" not only symbolizes the dramatic path of science stealing the energy of nuclear fission from nature and mastering this energy, but also warns people against a terrible military danger.

Promethium is now obtained in considerable quantities: it is used in atomic batteries - sources of direct current, capable of operating without interruption for several years.

The heaviest halogen ekaiod element No. 85 was also synthesized in a similar way. It was first obtained by bombarding bismuth (No. 83) with helium nuclei (No. 2), accelerated in a cyclotron to high energies.

The nuclei of helium, the second element in the periodic table, have two charges. Therefore, for the synthesis of the 85th element, bismuth, the 83rd element, was taken. The new element is named astatine (unstable). It is radioactive and disappears quickly. Its chemical properties also turned out to correspond exactly to the periodic law. It looks like iodine.

transuranium elements.

Chemists have put a lot of work into searching for elements heavier than uranium in nature. More than once triumphant announcements appeared in scientific journals about the "reliable" discovery of a new "heavy" element with an atomic mass greater than that of uranium. For example, element No. 93 was "discovered" in nature many times, it received the names "bohemia", "sequania". But these "discoveries" turned out to be the result of errors. They characterize the difficulty of precise analytical determination of insignificant traces of a new unknown element with unexplored properties.

The result of these searches was negative, because there are practically no elements on Earth corresponding to those cells of the periodic table that should be located beyond the 92nd cell.

The first attempts to artificially obtain new elements heavier than uranium are associated with one of the most remarkable mistakes in the history of the development of science. It was noticed that under the influence of the neutron flux, many elements become radioactive and begin to emit β-rays. The nucleus of an atom, having lost a negative charge, shifts one cell to the right in the periodic system, and its serial number becomes one more - a transformation of elements occurs. Thus, under the influence of neutrons, heavier elements are usually formed.

They tried to act on uranium with neutrons. Scientists hoped that, like other elements, uranium would also have β-activity and, as a result of β-decay, a new element with a number greater than one would appear. It is he who will occupy the 93rd cell in the Mendeleev system. It was suggested that this element should be similar: to rhenium, so it was previously called ecarium.

The first experiments seemed to immediately confirm this assumption. Even more, it was found that in this case, not one new element arises, but several. Five new elements heavier than uranium have been reported. In addition to ecarium, ekaosmium, ekairidium, ekaplatinum and ekazoloto were "discovered". And all the discoveries turned out to be a mistake. But that was a remarkable mistake. It led science to the greatest achievement of physics in the history of mankind - to the discovery of the fission of uranium and the mastery of the energy of the atomic nucleus.

No transuranic elements have actually been found. With strange new elements, attempts were made in vain to find the supposed properties that the elements from ecarium and ecagold should have. And suddenly, among these elements, radioactive barium and lanthanum were unexpectedly discovered. Not transuranium, but the most common, but radioactive isotopes of elements, the places of which are in the middle of the periodic system of Mendeleev.

A little time passed, and this unexpected and very strange result was correctly understood.

Why, from the atomic nuclei of uranium, which is at the end of the periodic system of elements, under the action of neutrons, nuclei of elements are formed, the places of which are in its middle? For example, under the action of neutrons on uranium, elements appear corresponding to the following cells of the periodic system:

Many elements have been found in the unimaginably complex mixture of radioactive isotopes produced in neutron-irradiated uranium. Although they turned out to be old, long-familiar elements to chemists, at the same time they were new substances, first created by man.

In nature, there are no radioactive isotopes of bromine, krypton, strontium, and many other of the thirty-four elements - from zinc to gadolinium, that arise when uranium is irradiated.

It often happens in science: the most mysterious and most complex turns out to be simple and clear when it is unraveled and understood. When a neutron hits a uranium nucleus, it splits, splits into two fragments - into two atomic nuclei of smaller mass. These fragments can be of various sizes, which is why so many different radioactive isotopes of ordinary chemical elements are formed.

One atomic nucleus of uranium (92) decays into atomic nuclei of bromine (35) and lanthanum (57), fragments during the splitting of another may turn out to be atomic nuclei of krypton (36) and barium (56). The sum of the atomic numbers of the resulting fragmentation elements will be equal to 92.

This was the beginning of a chain of great discoveries. It was soon discovered that under the impact of a neutron, not only fragments arise from the nucleus of an atom of uranium-235 - nuclei with a lower mass, but also two or three neutrons fly out. Each of them, in turn, is capable of again causing the fission of the uranium nucleus. And with each such division, a lot of energy is released. This was the beginning of man's mastery of intra-atomic energy.

Among the huge variety of products arising from the irradiation of uranium nuclei with neutrons, the first real transuranium element No. 93, which remained unnoticed for a long time, was subsequently discovered. It arose under the action of neutrons on uranium-238. In terms of chemical properties, it turned out to be very similar to uranium and was not at all similar: to rhenium, as was expected during the first attempts to synthesize elements heavier than uranium. Therefore, they could not immediately detect it.

The first man-made element outside the "natural system of chemical elements" was named neptunium, after the planet Neptune. Its creation has expanded for us the boundaries defined by nature itself. Likewise, the predicted discovery of the planet Neptune has expanded the boundaries of our knowledge of the solar system.

Soon the 94th element was also synthesized. It was named after the last planet. solar system.

They called it plutonium. In Mendeleev's periodic system, it follows neptunium in order, similarly to "the last planet of the Solar * system, Pluto, whose orbit lies beyond the orbit of Neptune. Element No. 94 arises from neptunium during its β-decay.

Plutonium is the only transuranium element that is now produced in nuclear reactors in very large quantities. Like uranium-235, it is capable of fission under the influence of neutrons and is used as fuel in nuclear reactors.

Elements 95 and 96 are called americium and curium. They are also now produced in nuclear reactors. Both elements have very high radioactivity - they emit α-rays. The radioactivity of these elements is so great that concentrated solutions of their salts heat up, boil and glow very strongly in the dark.

All transuranium elements - from neptunium to americium and curium - were obtained in fairly large quantities. IN pure form these are silver-colored metals, all of them are radioactive and in terms of chemical properties they are somewhat similar to each other, and in some ways they differ noticeably.

The 97th element, berkelium, was also isolated in its pure form. To do this, it was necessary to place a pure preparation of plutonium inside a nuclear reactor, where it was exposed to a powerful neutron flux for six whole years. During this time, several micrograms of element No. 97 accumulated in it. Plutonium was removed from a nuclear reactor, dissolved in acid, and the longest-lived berkelium-249 was isolated from the mixture. It is highly radioactive - it decays by half in a year. So far, only a few micrograms of Berkelium have been obtained. But this amount was enough for scientists to accurately study its chemical properties.

Element number 98 is very interesting - californium, the sixth after uranium. Californium was first created by bombarding a curium target with alpha particles.

The history of the synthesis of the next two transuranium elements: 99th and 100th is fascinating. For the first time they were found in the clouds and in the "mud". To study what is formed in thermonuclear explosions, the aircraft flew through the explosive cloud, and sediment samples were collected on paper filters. Traces of two new elements were found in this sediment. To get more accurate data, they collected a large number of"mud" - altered by the explosion of soil and rock. This "dirt" was processed in the laboratory, and two new elements were isolated from it. They were named einsteinium and fermium, in honor of the scientists A. Einstein and E. Fermi, to whom humanity is primarily obliged by the discovery of ways to master atomic energy. Einstein owns the law of equivalence of mass and energy, and Fermi built the first atomic reactor. Now einsteinium and fermium are also obtained in laboratories.

Elements of the second hundred.

Not so long ago, hardly anyone could believe that the symbol of the hundredth element would be included in the periodic table.

The artificial synthesis of elements did its job: for a short time, fermium closed the list of known chemical elements. The thoughts of scientists were now directed into the distance, to the elements of the second hundred.

But on the way there was a barrier, which was not easy to overcome.

So far, physicists have been synthesizing new transuranium elements mainly in two ways. Or they fired at targets from transuranium elements, already synthesized, with α-particles and deuterons. Or they bombarded uranium or plutonium with powerful neutron fluxes. As a result, isotopes of these elements very rich in neutrons were formed, which, after several successive β-decays, turned into isotopes of new transuraniums.

However, in the mid-1950s, both of these possibilities were exhausted. In nuclear reactions, it was possible to obtain imponderable amounts of einsteinium and fermium, and therefore it was impossible to make targets from them. The neutron method of synthesis also did not allow one to advance beyond fermium, since the isotopes of this element underwent spontaneous fission with a much higher probability than β decay. It is clear that under such conditions it made no sense to talk about the synthesis of a new element.

Therefore, physicists took the next step only when they managed to accumulate the minimum amount of element No. 99 required for the target. This happened in 1955.

One of the most remarkable achievements that science can rightfully be proud of is the creation of the 101st element.

This element was named after the great creator of the periodic table of chemical elements, Dmitri Ivanovich Mendeleev.

Mendelevium was obtained in the following way. An invisible coating of approximately one billion einsteinium atoms was applied to a sheet of the thinnest gold foil. Alpha particles with very high energy, breaking through gold foil with reverse side, upon collision with einsteinium atoms could enter into a nuclear reaction. As a result, atoms of the 101st element were formed. With such a collision, the mendelevium atoms flew out from the surface of the gold foil and collected on another, located next to it, the thinnest gold leaf. In this ingenious way, it was possible to isolate the pure atoms of element 101 from a complex mixture of einsteinium and its decay products. Invisible plaque was washed off with acid and subjected to radiochemical research.

Truly it was a miracle. The source material for the creation of the 101st element in each individual experiment was approximately one billion einsteinium atoms. This is very little less than one billionth of a milligram, and to get einsteinium in more was impossible. It was calculated in advance that out of a billion einsteinium atoms, under many hours of bombardment with α-particles, only one single atom of einsteinium can react and, consequently, only one atom of a new element can be formed. It was necessary not only to be able to detect it, but also to do it in such a way as to find out from just one atom the chemical nature of the element.

And it was done. The success of the experiment exceeded calculations and expectations. It was possible to notice in one experiment not one, but even two atoms of a new element. In total, seventeen mendelevium atoms were obtained in the first series of experiments. This turned out to be enough to establish both the fact of the formation of a new element and its place in the periodic system and to determine its basic chemical and radioactive properties. It turned out that this is an α-active element with a half-life of about half an hour.

Mendelevium - the first element of the second hundred - turned out to be a kind of milestone on the way to the synthesis of transuranium elements. Until now, it remains the last of those that were synthesized by the old methods - irradiation with α-particles. Now more powerful projectiles have entered the scene - accelerated multiply charged ions of various elements. Determination of the chemical nature of mendelevium by a counted number of its atoms laid the foundation for a completely new scientific discipline - the physicochemistry of single atoms.

The symbol of element No. 102 No - in the periodic system is taken in brackets. And in these brackets lies a long and complicated history of this element.

The synthesis of nobelium was reported in 1957 by an international group of physicists working at the Nobel Institute (Stockholm). For the first time, heavy accelerated ions were used to synthesize a new element. They were 13 C ions, the flow of which was directed to the curium target. The researchers came to the conclusion that they managed to synthesize an isotope of the 102nd element. He was given the name in honor of the founder of the Nobel Institute, the inventor of dynamite, Alfred Nobel.

A year has passed, and the experiments of the Stockholm physicists were reproduced almost simultaneously in the Soviet Union and the USA. And an amazing thing turned out: the results of Soviet and American scientists had nothing in common either with the work of the Nobel Institute or with each other. No one and nowhere else has been able to repeat the experiments carried out in Sweden. This situation gave rise to a rather sad joke: "There is only one No left from Nobel" (No - translated from English means "no"). The symbol, hastily placed on the periodic table, did not reflect the actual discovery of the element.

A reliable synthesis of element No. 102 was made by a group of physicists from the Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. In 1962-1967. Soviet scientists synthesized several isotopes of element No. 102 and studied its properties. Confirmation of these data was obtained in the United States. However, the symbol No, having no right to do so, is still in the 102nd cell of the table.

Lawrencium, element No. 103 with the symbol Lw, named after the inventor of the cyclotron E. Lawrence, was synthesized in 1961 in the USA. But here the merit of the Soviet physicists is no less. They obtained several new isotopes of lawrencium and studied the properties of this element for the first time. Lawrencium also came into being through the use of heavy ions. The Californian target was irradiated with boron ions (or the americium target with oxygen ions).

Element No. 104 was first obtained by Soviet physicists in 1964. Bombardment of plutonium with neon ions led to its synthesis. The 104th element was named kurchatovium (symbol Ki) in honor of the outstanding Soviet physicist Igor Vasilyevich Kurchatov.

The 105th and 106th elements were also synthesized for the first time by Soviet scientists - in 1970 and in 1974. The first of these, the product of the bombardment of americium with neon ions, was named nilsborium (Ns) in honor of Niels Bohr. The synthesis of the other was carried out as follows: a lead target was bombarded with chromium ions. Syntheses of elements 105 and 106 were also carried out in the USA.

You will learn about this in the next chapter, and we will conclude the present one with a short story about how

how to study the properties of the elements of the second hundred.

A fantastically difficult task confronts experimenters.

Here are its initial conditions: a few quantities (tens, at best hundreds) of atoms of a new element are given, and atoms are very short-lived (half-lives are measured in seconds, or even fractions of a second). It is required to prove that these atoms are atoms of a really new element (i.e., to determine the value of Z, as well as the value of the mass number A, in order to know which isotope of the new transuranium is in question), and to study its most important chemical properties.

A few atoms, a tiny lifespan...

Scientists come to the aid of speed and the highest ingenuity. But a modern researcher - a specialist in the synthesis of new elements - must not only be able to "shoe a flea". He must also be fluent in theory.

Let us follow the basic steps by which a new element is identified.

the most important calling card first of all, radioactive properties serve; this can be the emission of α-particles or spontaneous fission. Each α-active nucleus is characterized by specific energies of α-particles. This circumstance makes it possible either to identify known nuclei or to conclude that new ones have been discovered. For example, by studying the features of α-particles, scientists were able to obtain reliable evidence of the synthesis of the 102nd and 103rd elements.

The energetic fragmentation nuclei formed as a result of fission are much easier to detect than α-particles, due to the much higher energy of the fragments. For their registration, plates made of glass of a special grade are used. The fragments leave slightly noticeable traces on the surface of the plates. The plates are then chemically treated (etched) and carefully examined under a microscope. Glass dissolves in hydrofluoric acid.

If a glass plate, fired with fragments, is placed in a solution of hydrofluoric acid, then in places where the fragments have fallen, the glass will dissolve faster and holes will form there. Their dimensions are hundreds of times larger than the original trace left by the fragment. The wells can be observed under a microscope at low magnification. Other radioactive emissions cause less damage to glass surfaces and are not visible after etching.

Here is what the authors of the synthesis of kurchatovium tell about how the process of identifying a new element took place: “An experiment is underway. For forty hours, neon nuclei are continuously bombarding a plutonium target. For forty hours, the tape carries synthetic nuclei to glass plates. Finally, the cyclotron is turned off. "We look forward to the result. Several hours pass. Under the microscope, six tracks were found. From their position, the half-life was calculated. It turned out to be in the time interval from 0.1 to 0.5 s."

And here is how the same researchers talk about the assessment of the chemical nature of kurchatovium and nilsborium. "The scheme for studying the chemical properties of element No. 104 is as follows. The recoil atoms exit the target into a nitrogen jet, are decelerated in it, and then chlorinated. Compounds of the 104th element with chlorine easily penetrate through a special filter, but all actinides do not pass. If the 104th belonged to the actinoid series, then it would have been delayed by the filter.However, studies have shown that the 104th element is a chemical analogue of hafnium.This is the most important step towards filling the periodic table with new elements.

Then the chemical properties of the 105th element were studied in Dubna. It turned out that its chlorides are adsorbed on the surface of the tube along which they move from the target at a temperature lower than hafnium chlorides, but higher than niobium chlorides. Only atoms of an element close in chemical properties to tantalum could behave in this way. Look at the periodic table: the chemical analogue of tantalum is element number 105! Therefore, experiments on adsorption on the surface of atoms of the 105th element confirmed that its properties coincide with those predicted on the basis of the periodic system.

, plutonium), in the photospheres of stars (technetium and, possibly, promethium), in supernova shells (californium and, probably, its decay products - berkelium, curium, americium and lighter ones).

The last element found in nature before it was synthesized artificially was francium (1939). The first chemical element to be synthesized was technetium in 1937. As of 2012, elements have been synthesized by nuclear fusion or decay to ununoctium with atomic number 118, and attempts have also been made to synthesize the following superheavy transuranium elements. Synthesis of new transactinoid and superactinoid continues.

The most famous laboratories that have synthesized several new elements and several tens or hundreds of new isotopes are the National Laboratory. Lawrence at Berkeley and Livermore National Laboratory (USA), in Dubna (USSR/Russia), European (Germany), Cambridge University Cavendish Laboratory (Great Britain), (Japan) and others. In recent decades, the synthesis of elements in American, German and international teams work in Russian centers.

Discovery of synthesized elements by country

USSR, Russia

USA

Germany

Controversial priorities and shared results

For a number of elements, the priority is equally approved according to the decision of the joint commission of IUPAC and IUPAP or remains controversial:

USA and Italy

Russia and Germany

Russia and Japan

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An excerpt characterizing the synthesized chemical elements

- What are we going to do with them? - Convulsively sighing, she pointed to the kids who had huddled together, Stella. - You can't leave it here.
I didn’t have time to answer when a calm and very sad voice sounded:
"I'll stay with them, if you'll let me, of course."
Together we jumped up and turned around - this was the man saved by Mary speaking ... And somehow we completely forgot about him.
- How are you feeling? – I asked as friendly as possible.
I honestly did not wish harm to this unfortunate stranger, saved at such a high price. It wasn't his fault, and Stella and I knew that very well. But the terrible bitterness of the loss still clouded my eyes with anger, and although I knew that this was very, very unfair to him, I could not pull myself together and push this terrible pain out of myself, leaving it "for later" when I all alone, and, closing myself “in my corner”, I can give vent to bitter and very heavy tears ... I was also very afraid that the stranger would somehow feel my “rejection”, and thus his release would lose that importance and beauty victory over evil, in the name of which my friends died ... Therefore, I tried my best to gather myself and, smiling as sincerely as possible, waited for an answer to my question.
The man sadly looked around, apparently not quite understanding what had happened here, and what was happening to him all this time...
- Well, where am I? .. - he asked quietly in a voice hoarse with excitement. What is this place, so terrible? It doesn't look like what I remember... Who are you?
- We are friends. And you are absolutely right - this is not a very pleasant place ... And a little further, the places are generally wildly scary. Our friend lived here, he died...
“I'm sorry, little ones. How did your friend die?
“You killed him,” Stella whispered sadly.
I froze, staring at my girlfriend ... This was not said by the “sunny” Stella, who was well known to me, who “without fail” felt sorry for everyone, and would never make anyone suffer! .. But, apparently, the pain of loss, like me, it aroused in her an unconscious feeling of anger “at everyone and everything”, and the baby was not yet able to control it in herself.
– Me?!.. – exclaimed the stranger. But that can't be true! I have never killed anyone!
We felt that he was telling the pure truth, and we knew that we had no right to shift the blame on him. Therefore, without even saying a word, we smiled together and immediately tried to quickly explain what really happened here.
The man was in a state of absolute shock for a long time ... Apparently, everything he heard sounded wild to him, and certainly did not coincide with what he really was, and how he treated such a terrible evil that did not fit into normal human frames. ...
- How can I compensate for all this?! .. After all, I can’t do it? And how to live with it?!.. - he clutched his head... - How many I killed, tell me!.. Can anyone say that? What about your friends? Why did they go for it? But why?!!!..
- So that you can live as you should ... As you wanted ... And not as someone wanted ... To kill the Evil that killed others. Because, probably ... - Stella said sadly.
“Forgive me, dear ones... Forgive me... If you can...” the man looked completely killed, and I was suddenly “pricked” with a very bad premonition...
- Well, I do not! I exclaimed indignantly. “Now you must live!” Do you want to nullify all their sacrifice?! Don't even dare to think! Now you will do good instead of them! That will be right. And leaving is the easiest thing. And you no longer have that right.
The stranger stared at me dumbfounded, apparently not expecting such a violent outburst of "righteous" indignation. And then he smiled sadly and said quietly:
- How did you love them! .. Who are you, girl?
My throat was very tight and for some time I could not squeeze out a word. It was very painful because of such a heavy loss, and, at the same time, I was sad for this "restless" person, who would be oh so difficult to exist with such a burden...
- I am Svetlana. And this is Stella. We're just walking around here. We visit friends or help someone when we can. True, now there are no friends left ...
- Forgive me, Svetlana. Although it probably won't change anything if I ask your forgiveness every time... What happened happened, and I can't change anything. But I can change what happens, can't I? - the man glared at me with his blue eyes, like the sky, and, smiling, with a sad smile, said: - And one more thing ... You say that I am free in my choice? .. But it turns out - not so free, dear .. Rather, it looks like atonement for guilt ... With which I agree, of course. But it's your choice that I have to live for your friends. Because they gave their lives for me.... But I didn't ask for it, did I?.. Therefore, it's not my choice...

Of the 26 currently known transuranium elements, 24 are not found on our planet. They were created by man. How are heavy and superheavy elements synthesized?
The first list of thirty-three supposed elements, "The Table of Substances belonging to all the kingdoms of nature, which may be considered the simplest constituents of bodies", was published by Antoine Laurent Lavoisier in 1789. Together with oxygen, nitrogen, hydrogen, seventeen metals, and a few other real elements, light, caloric, and some oxides figured in it. And when Mendeleev came up with the Periodic Table 80 years later, chemists knew 62 elements. By the beginning of the 20th century, it was believed that there were 92 elements in nature - from hydrogen to uranium, although some of them had not yet been discovered. Nevertheless, already at the end of the 19th century, scientists admitted the existence of elements that follow uranium (transuranes) in the periodic table, but could not find them. It is now known that the earth's crust contains trace amounts of the 93rd and 94th elements - neptunium and plutonium. But historically, these elements were first obtained artificially and only then discovered in the composition of minerals.
Of the 94 first elements, 83 have either stable or long-lived isotopes, the half-life of which is comparable to the age of the solar system (they came to our planet from a protoplanetary cloud). The life of the remaining 11 natural elements is much shorter, and therefore they arise in the earth's crust only as a result of radioactive decays into short time. But what about all the other elements, from the 95th to the 118th? There are none on our planet. All of them were obtained artificially.
First artificial
The creation of artificial elements has long history. The fundamental possibility of this became clear in 1932, when Werner Heisenberg and Dmitry Ivanenko came to the conclusion that atomic nuclei consist of protons and neutrons. Two years later, Enrico Fermi's group attempted to produce transuranium by irradiating uranium with slow neutrons. It was assumed that the uranium nucleus will capture one or two neutrons, after which it will undergo beta decay with the birth of the 93rd or 94th elements. They were even quick to announce the discovery of transurans, which Fermi called ausonium and hesperium in his 1938 Nobel speech. However, the German radiochemists Otto Hahn and Fritz Strassmann, together with the Austrian physicist Lise Meitner, soon showed that Fermi was wrong: these nuclides were isotopes of already known elements, resulting from the fission of uranium nuclei into pairs of fragments of approximately the same mass. It was this discovery, made in December 1938, that made it possible to create a nuclear reactor and an atomic bomb. The first synthesized element was not transuranium at all, but ecamarganese predicted by Mendeleev. It was searched for in various ores, but without success. And in 1937, ecamarganese, later called technetium (from the Greek ??? - artificial) was obtained by shelling a molybdenum target with deuterium nuclei accelerated in the cyclotron at the Lawrence Berkeley National Laboratory.
Light projectiles
Elements from 93rd to 101st were obtained by the interaction of uranium nuclei or transuraniums following it with neutrons, deuterons (deuterium nuclei) or alpha particles (helium nuclei). The first success here was achieved by the Americans Edwin Macmillan and Philip Abelson, who in 1940 synthesized neptunium-239, having worked out Fermi's idea: the capture of slow neutrons by uranium-238 and the subsequent beta decay of uranium-239. The next, 94th element - plutonium - was first discovered while studying the beta decay of neptunium-238 produced by deuteron bombardment of uranium at the UC Berkeley cyclotron in early 1941. And it soon became clear that plutonium-239, under the action of slow neutrons, fissions no worse than uranium-235 and can serve as the filling of an atomic bomb. Therefore, all information about the receipt and properties of this element was classified, and the article by Macmillan, Glenn Seaborg (for their discoveries they shared Nobel Prize 1951) and their colleagues with a message about the second transuranium appeared in print only in 1946. The American authorities also delayed the publication of the discovery of the 95th element, americium, which at the end of 1944 was isolated by the Seaborg group from neutron bombardment products for almost six years. plutonium in a nuclear reactor. A few months earlier, physicists on the same team had obtained the first isotope of element 96, with an atomic weight of 242, synthesized by bombarding uranium-239 with accelerated alpha particles. It was named curium in recognition of the scientific merit of Pierre and Marie Curie, thus opening up the tradition of naming transuraniums in honor of the classics of physics and chemistry. . The first two were named after their birthplace - Berkeley and California. Berkelium was synthesized in December 1949 during the bombardment of americium with alpha particles, and californium two months later with the same bombardment of curium. Elements 99 and 100, einsteinium and fermium, were discovered during radiochemical analysis of samples collected in the Eniwetok Atoll area, where on November 1, 1952, the Americans detonated the Mike ten-megaton thermonuclear charge, the shell of which was made of uranium-238. During the explosion, uranium nuclei absorbed up to fifteen neutrons, after which they underwent chains of beta decays, which led to the formation of these elements. Element 101, mendelevium, was obtained in early 1955. Seaborg, Albert Ghiorso, Bernard Harvey, Gregory Choppin, and Stanley Thomson alpha-particle bombarded about a billion (very few, but there were simply no more) einsteinium atoms electrolytically deposited on gold foil. Despite the extremely high beam density (60 trillion alpha particles per second), only 17 mendelevium atoms were obtained, but at the same time it was possible to establish their radiation and chemical properties.
heavy ions
Mendelevium was the last transuranium produced using neutrons, deuterons, or alpha particles. To obtain the following elements, targets from element number 100, fermium, were required, which were then impossible to manufacture (even now, fermium is produced in nanogram quantities in nuclear reactors). Scientists went the other way: they used ionized atoms to bombard targets, whose nuclei contain more than two protons ( they are called heavy ions). To accelerate ion beams, specialized accelerators were required. The first such machine HILAC (Heavy Ion Linear Accelerator) was launched in Berkeley in 1957, the second, the U-300 cyclotron, was launched at the Nuclear Reactions Laboratory of the Joint Institute for Nuclear Research in Dubna in 1960. Later, more powerful U-400 and U-400M installations were launched in Dubna. Another accelerator UNILAC (Universal Linear Accelerator) has been operating since the end of 1975 at the German Helmholtz Center for Heavy Ion Research, in Vixhausen, one of the districts of Darmstadt. During heavy ion bombardment of targets made of lead, bismuth, uranium or transuranium, strongly excited hot) nuclei that either fall apart or release excess energy through the emission (evaporation) of neutrons. Sometimes these nuclei emit one or two neutrons, after which they undergo other transformations - for example, alpha decay. This type of synthesis is called cold. In Darmstadt, with his help, elements with numbers from 107 (borium) to 112 (copernicium) were obtained. In the same way, in 2004, Japanese physicists created one atom of the 113th element (a year earlier it was obtained in Dubna). During hot fusion, newborn nuclei lose more neutrons - from three to five. In this way, elements from 102 (nobelium) to 106 (seaborgium, in honor of Glenn Seaborg, under whose leadership nine new elements were created) were synthesized in Berkeley and Dubna. Later, in Dubna, six of the most massive superheavyweights were made in this way - from 113 to 118. international union of theoretical and applied chemistry (IUPAC, International Union of Pure and Applied Chemistry) has so far approved only the names of the 114th (flerovium) and 116th (livermorium) elements.
Only three atoms
The 118th element with the temporary name of ununoctia and the symbol Uuo (according to IUPAC rules, the temporary names of elements are formed from the Latin and Greek roots of the names of the digits of their atomic number, un-un-oct (ium) - 118) was created by the joint efforts of two scientific groups: Dubninskaya under the direction of Yuri Oganesyan and Livermore National Laboratory under the direction of Kenton Moody, a student of Seaborg. Ununoctium in the periodic table is located under radon and therefore can be a noble gas. However, its chemical properties have not yet been clarified, since physicists have created only three atoms of this element with a mass number of 294 (118 protons, 176 neutrons) and a half-life of about a millisecond: two in 2002 and one in 2005. They were obtained by bombarding a californium-249 target (98 protons, 151 neutrons) with ions of a heavy calcium isotope with an atomic mass of 48 (20 protons and 28 neutrons), dispersed at the U-400 accelerator. The total number of calcium "bullets" was 4.1x1019, so the performance of the Dubna "ununoctium generator" is extremely low. However, according to Kenton Moody, the U-400 is the only machine in the world that could synthesize the 118th element. “Each series of experiments on the synthesis of transuraniums adds new information about the structure of nuclear matter, which is used to model the properties of superheavy nuclei. In particular, work on the synthesis of the 118th element made it possible to discard several previous models, recalls Kenton Moody. - We made the target out of california, since the heavier elements in the right quantities were unavailable. Calcium-48 contains eight extra neutrons compared to its main isotope calcium-40. When its nucleus merged with a californium nucleus, nuclei with 179 neutrons were formed. They were in highly excited and therefore especially unstable states, from which they quickly exited, dropping neutrons. As a result, we got an isotope of the 118th element with 176 neutrons. And these were real neutral atoms with a full set of electrons! Had they lived a little longer, it would have been possible to judge their chemical properties».
Methuselah number 117
Element 117, also known as ununseptium, was obtained later - in March 2010. This element was produced on the same U-400 machine, where, as before, calcium-48 ions were fired at a target from berkelium-249, synthesized at the Oak Ridge National Laboratory. The collision of berkelium and calcium nuclei produced highly excited ununseptium-297 nuclei (117 protons and 180 neutrons). The experimenters managed to get six nuclei, five of which evaporated four neutrons each and turned into ununseptium-293, and the rest emitted three neutrons and gave rise to ununseptium-294. In comparison with ununoctium, unununseptium turned out to be a real Methuselah. The half-life of the lighter isotope is 14 milliseconds, and that of the heavier one is as much as 78 milliseconds! In 2012, physicists from Dubna received five more atoms of ununseptium-293, later - several atoms of both isotopes. In the spring of 2014, scientists from Darmstadt reported the fusion of four nuclei of the 117th element, two of which had an atomic mass of 294. The half-life of this "heavy" ununseptium, measured by German scientists, was about 51 milliseconds (this is in good agreement with the estimates of scientists from Dubna) .Now in Darmstadt they are preparing a project for a new linear accelerator of heavy ions on superconducting magnets, which will allow the synthesis of the 119th and 120th elements. Similar plans are being implemented in Dubna, where a new DS-280 cyclotron is being built. It is possible that in just a few years the synthesis of new superheavy transuraniums will become possible. And the creation of the 120th or even the 126th element with 184 neutrons and the discovery of the island of stability will become a reality.
Long life on the island of stability
Inside the nuclei there are proton and neutron shells, somewhat similar to the electron shells of atoms. Nuclei with completely filled shells are especially resistant to spontaneous transformations. The numbers of neutrons and protons corresponding to such shells are called magic numbers. Some of them are determined experimentally - these are 2, 8, 20 and 28.Shell models make it possible to calculate the "magic numbers" of superheavy nuclei theoretically, though without a full guarantee. There are reasons to expect that the neutron number 184 will turn out to be magical. The proton numbers 114, 120 and 126 can correspond to it, and the latter, again, must be magic. If this is so, then the isotopes of the 114th, 120th and 126th elements, containing 184 neutrons each, will live much longer than their neighbors in the periodic table - minutes, hours, or even years (this area of ​​\u200b\u200bthe table is commonly called the island of stability ). Scientists pin their greatest hopes on the last isotope with a doubly magic nucleus.
Dubna method

When a heavy ion enters the region of the nuclear forces of the target, a compound nucleus in an excited state can be formed. It either decays into fragments of approximately equal mass, or emits (evaporates) several neutrons and passes into the ground (unexcited) state.
“Elements 113 to 118 were created on the basis of a wonderful method developed in Dubna under the guidance of Yuri Oganesyan,” explains Alexander Yakushev, a member of the Darmstadt team. - Instead of nickel and zinc, which were used for shelling targets in Darmstadt, Oganesyan took an isotope with a much lower atomic mass - calcium-48. The point is that the use of light nuclei increases the probability of their fusion with target nuclei. The calcium-48 nucleus is also doubly magical, since it is composed of 20 protons and 28 neutrons. Therefore, the choice of Oganesyan greatly contributed to the survival of the compound nuclei that arise during the shelling of the target. After all, the nucleus can throw off several neutrons and give rise to a new transuranium only if it does not fall apart into fragments immediately after birth. In order to synthesize superheavy elements in this way, the Dubninsk physicists made targets from transuraniums produced in the USA - first plutonium, then americium, curium, California, and finally berkelium. Calcium-48 in nature is only 0.7%. It is extracted on electromagnetic separators, this is an expensive procedure. One milligram of this isotope costs about $200. This amount is enough for an hour or two of shelling the target, and the experiments last for months. The targets themselves are even more expensive, reaching a million dollars. Paying electricity bills also costs a pretty penny - heavy ion accelerators consume megawatts of power. In general, the synthesis of superheavy elements is not a cheap pleasure.”