Нихоний: Жаңа элементтің ашылуы мен қасиеттері

Nihonium is a synthetic chemical element; it has symbol Nh and atomic number 113. It is extremely radioactive: its most stable known isotope, nihonium 286, has a half life of about 10 seconds. In the periodic table, nihonium is a transactinide element in the p block. It is a member of period 7 and group 13. Nihonium was first reported to have been created in 2003 by a Russian–American collaboration at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and in 2004 by a team of Japanese scientists at Riken in Wakō, Japan. The confirmation of their claims in the ensuing years involved independent teams of scientists working in the United States, Germany, Sweden, and China, as well as the original claimants in Russia and Japan. In 2015, the IUPAC/IUPAP Joint Working Party recognised the element and assigned the priority of the discovery and naming rights for the element to Riken. The Riken team suggested the name nihonium in 2016, which was approved in the same year. The name comes from the common Japanese name for Japan (日本). Very little is known about nihonium, as it has only been made in very small amounts that decay within seconds. The anomalously long lives of some superheavy nuclides, including some nihonium isotopes, are explained by the "island of stability" theory. Experiments support the theory, with the half lives of the confirmed nihonium isotopes increasing from milliseconds to seconds as neutrons are added and the island is approached. Nihonium has been calculated to have similar properties to its homologues boron, aluminium, gallium, indium, and thallium. All but boron are post transition metals, and nihonium is expected to be a post transition metal as well. It should also show several major differences from them; for example, nihonium should be more stable in the +1 oxidation state than the +3 state, like thallium, but in the +1 state nihonium should behave more like silver and astatine than thallium. Preliminary experiments in 2017 showed that elemental nihonium is not very volatile; its chemistry remains largely unexplored.

Superheavy element

In December 2015, the conclusions of a new JWP report were published by IUPAC in a press release, in which element 113 was awarded to Riken; elements 115, 117, and 118 were awarded to the collaborations involving the JINR. The JINR considered the awarding of element 113 to Riken unexpected, citing their own 2003 production of elements 115 and 113, and pointing to the precedents of elements 103, 104, and 105 where IUPAC had awarded joint credit to the JINR and LBNL. They stated that they respected IUPAC's decision, but reserved determination of their position for the official publication of the JWP reports. The full JWP reports were published on 21 January 2016. The JWP recognised the discovery of element 113, assigning priority to Riken. They noted that while the individual decay energies of each nuclide in the decay chain of 278113 were inconsistent, their sum was now confirmed to be consistent, strongly suggesting that the initial and final states in 278113 and its daughter 262Db were the same for all three events. The decay of 262Db to 258Lr and 254Md was previously known, firmly anchoring the decay chain of 278113 to known regions of the chart of nuclides. The JWP considered that the JINR–LLNL collaborations of 2004 and 2007, producing element 113 as the daughter of element 115, did not meet the discovery criteria as they had not convincingly determined the atomic numbers of their nuclides through cross bombardments, which were considered necessary since their decay chains were not anchored to previously known nuclides. They also considered that the previous JWP's concerns over their chemical identification of the dubnium daughter had not been adequately addressed. The JWP recognised the JINR–LLNL–ORNL–Vanderbilt collaboration of 2010 as having discovered elements 117 and 115, and accepted that element 113 had been produced as their daughter, but did not give this work shared credit. After the publication of the JWP reports, Sergey Dimitriev, the lab director of the Flerov lab at the JINR where the discoveries were made, remarked that he was happy with IUPAC's decision, mentioning the time Riken spent on their experiment and their good relations with Morita, who had learnt the basics of synthesising superheavy elements at the JINR. Two members of the JINR team published a journal article rebutting these criticisms against the congruence of their data on elements 113, 115, and 117 in June 2017.

Using Mendeleev's nomenclature for unnamed and undiscovered elements, nihonium would be known as eka thallium. In 1979, IUPAC published recommendations according to which the element was to be called ununtrium (with the corresponding symbol of Uut), a systematic element name as a placeholder, until the discovery of the element is confirmed and a name is decided on. The recommendations were widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, but were mostly ignored among scientists in the field, who called it "element 113", with the symbol of E113, (113), or even simply 113. and rikenium, after the institute. After the recognition, the Riken team gathered in February 2016 to decide on a name. Morita expressed his desire for the name to honour the fact that element 113 had been discovered in Japan. Japonium was considered, making the connection to Japan easy to identify for non Japanese, but it was rejected as Jap is considered an ethnic slur. The name nihonium was chosen after an hour of deliberation: it comes from (日本), one of the two Japanese pronunciations for the name of Japan. The discoverers also intended to reference the support of their research by the Japanese people (Riken being almost entirely government funded), recover lost pride and trust in science among those who were affected by the Fukushima Daiichi nuclear disaster, In March 2016, Morita proposed the name "nihonium" to IUPAC, with the symbol Nh. Thus, IUPAC and IUPAP publicised the proposal of nihonium that June, and set a five month term to collect comments, after which the name would be formally established at a conference. The name was officially approved in November 2016. The naming ceremony for the new element was held in Tokyo, Japan, in March 2017, with Naruhito, then the Crown Prince of Japan, in attendance.

The heavier nihonium tribromide (NhBr3) and triiodide (NhI3) are trigonal planar due to the increased steric repulsion between the peripheral atoms; accordingly, they do not show significant 6d involvement in their bonding, though the large 7s–7p energy gap means that they show reduced sp2 hybridisation compared to their boron analogues. The +3 state is stabilised for thallium in anionic complexes such as TlI4 , and the presence of a possible vacant coordination site on the lighter T shaped nihonium trihalides is expected to allow a similar stabilisation of NhF4 and perhaps NhCl4 The isotopes 284Nh, 285Nh, and 286Nh have half lives long enough for chemical investigation. A 2017 experiment at the JINR, producing 284Nh and 285Nh via the 243Am+48Ca reaction as the daughters of 288Mc and 289Mc, avoided this problem by removing the quartz surface, using only PTFE. No nihonium atoms were observed after chemical separation, implying an unexpectedly large retention of nihonium atoms on PTFE surfaces. This experimental result for the interaction limit of nihonium atoms with a PTFE surface disagrees significantly with previous theory, which expected a lower value of 14.00 kJ/mol. This suggests that the nihonium species involved in the previous experiment was likely not elemental nihonium but rather nihonium hydroxide, and that high temperature techniques such as vacuum chromatography would be necessary to further probe the behaviour of elemental nihonium. Bromine saturated with boron tribromide has been suggested as a carrier gas for experiments on nihonium chemistry; this oxidises nihonium's lighter congener thallium to thallium(III), providing an avenue to investigate the oxidation states of nihonium, similar to earlier experiments done on the bromides of group 5 elements, including the superheavy dubnium.