Chemistry students will now have much more material to memorize than in the days of Dmitry Mendeleev (February 8, 1834 – February 2, 1907), the Russian scientist who played cards with the 63 elements known to date in 1869 and drew up the first version of the periodic table, which has been expanding ever since with a regular net of new members. Until the arrival of flerovium (114) and livermorium (116), appointed in May 2012, the work of chemists became increasingly difficult; Francium (87), discovered by Marguerite Perey in January 1939, marked the end of the era of the discovery of new elements in nature. Two years earlier, the era of synthetic elements with technetium (43) had been inaugurated, which was confirmed by scientists from the University of Palermo in December 1936. The strict boundary between nature and the laboratory is marked by plutonium (94), the heaviest element with isotopes stable enough to be found in the Earth`s crust. In addition, Americium (95) and Curium (96), both created in 1944, opened the field of the periodic table, which belongs exclusively to the laboratory or, at most, to experiments of human origin or nuclear accidents. Hydrogen has no fixed position in the modern periodic table, similar to Mendeleev`s periodic table. Hydrogen can be classified in group 1 or group 17 during the first period, as it has similarities in properties with both groups. The boundaries of Mendeleev`s periodic table are: ununtrium, ununpentium, ununseptium and ununoctium. These are convoluted terms, but they are only preliminary systematic names; Soon, they will be replaced by definitive elements, as science will publish these four new chemical elements on September 30.
December 2015. Their temporary names refer to their atomic numbers (Z) or the number of protons: 113, 115, 117 and 118, respectively. With these four new additions, all gaps in the seventh row of the periodic table of elements are filled. 1. Based on atomic number – The arrangement of elements in the modern periodic table corresponds to their increasing atomic number. The atomic number increases by 1 unit (unbroken) when passing from one element to another element and is equal to the number of electrons. Thus, the modern periodic table is easy to reproduce and remember like Mendeleev`s periodic table. Therefore, one would expect that exceeding the new limit of the periodic table up to the eighth row would be unthinkable. The calcium bombardment exposed six new elements, but as physicist David Hinde, director of the Heavy Ion Accelerator at the Australian National University, told OpenMind: “The difficulty of going beyond element 118 is that the use of a Ca-48 projectile, which has many favorable properties, is no longer possible; Heavier projectiles must be used.
However, Hinde is one of the men who could hold the key to move to the next square in the periodic table. Recently, he has studied the use of other projectiles in collaboration with the Superheavy Elements group at Mainz University and the GSI Center in Germany. The problem with using large-caliber projectiles, he explains, is that they “reduce the performance of superheavy elements by a factor of 10 or more.” Possibilities mentioned by Hinde include titanium-50, chromium-54, iron-58 and nickel-64. The prediction of a new element, the position in the periodic table, and the properties of new and other elements could be made precisely if the elements are arranged in ascending order of atomic number. This was not possible in Mendeleev`s periodic table, because atomic masses never increase steadily. Mendeleev arranges the elements in ascending order of their atomic masses. According to Mendeleev, physical and chemical properties are the periodic function of their atomic mass. What criteria did Mendeleev use to create his periodic table? Another difficulty is the increasing instability of the heavier elements, leaving little time for researchers to study their properties. But fortunately, that doesn`t always seem to be the case.
In the 1960s, Nobel laureate Glenn T. Seaborg suggested that “islands of stability” could appear in higher atomic numbers. The hypothesis is based on the idea that protons and neutrons in the nucleus are arranged in energy layers with a certain capacitance; The maximum occupation of these layers provides more stable “magic numbers” than their lighter atomic neighbors. The prediction applies to the isotope 208 of lead, with twice the magic number for protons (82) and neutrons (126), and which is actually the heaviest stable nucleus. Predictions vary for the next possible magic number of protons, but some scientists place it at element 120, or unbinilium. 3. Justification for the anomalous position of certain pairs of elements – Physicist Jadambaa Khuyagbaatar, who belongs to the German group working with Hinde and led the experiments to confirm element 117, is optimistic: “The results give us good hopes of synthesizing at least the next two elements, 119 and 120”, although “the experiments could take longer than for the synthesis of elements 114 to 118”, he advises OpenMind. And according to Hinde, it may not be enough to change the bullets, but perhaps more powerful guns will also be needed: “New accelerators with a higher flow of beam particles will help overcome this disadvantage.” Technetium, so called precisely because of its artificial origin, is one of many elements that were created synthetically before they were also discovered in nature.
But as atoms become heavier, unstable radioactive elements are created that can only be made in the lab and break down quickly, sometimes in small fractions of a second. Such as Co and Ni, Te and I, etc. By organizing them in order of ascending atomic number, these elements are arranged in groups with similar properties, which was the limitation of Mendeleev`s periodic table. Isotopes of an element have different atomic weights, but the same atomic number. Therefore, in the modern periodic table, there is no confusion in their position, since all isotopes of an element are placed in the same place due to the same atomic number. For example, C12, C13 and C14 – the three isotopes of carbon have the same atomic number 12 and are classified in group 14 and the 1st period. For Hinde, conquering this island could be a complicated undertaking, “or even impossible, depending on where the center is located.” However, the treasure hidden there could make up for the effort: “These cores in the center of the island are unlikely to be actually stable, but should have measured lifespan in many years, rather than seconds or less, like today`s super-heavy.” And according to Khuyagbaatar, at least we went ashore. “We are still far from the center of the island; However, its coastline has been reached. Scientists are able to synthesize these superheavy elements by pulling atoms against each other in the hope that they will fuse together, which happens only once in billions of collisions. In this way, the limit of element 118 was reached, the heaviest of the most recent arrivals. For example, element 117 was obtained by scientists from the United States and Russia who bombarded a 22-milligram sample of berkelium (element 97) with ions of the calcium isotope 48 for 150 days at the heavy ion accelerator of the Joint Nuclear Research Institute in the Russian city of Dubna.
In return, the berkelium took 250 days to be extracted by the Oak Ridge National Laboratory in the United States. And all these efforts managed to create only six atoms of element 117, which decayed in milliseconds.