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1St Cover Aug 2017 Issue.Indd FEATURE ARTICLE M.S.S. MURTHY New Members to the Periodic Table number 101 and neutron number153). Nihonium. Mc-290 had the longest During the course of their experiments half-life of 0.8 seconds. Element 117, the Japanese scientists identified six Tennessine was found to have two isotopes of Nh, all radioactive. The most isotopes Ts-293 and Ts-294 which decay OUR new elements discovered stable was Nh-286 with a half life of 20 to Mc-289 and Mc-290 with half-life 20 in December 2015 have recently milliseconds. With its atomic number and 50 milliseconds respectively. been named by the International 113, Nh is placed in the 13th group of Moscovium and Tennessine belong F th th Union of Pure and Applied Chemistry the periodic table along with elements to the 15 and 17 groups of the periodic (IUPAC). The names are: Nihonium like boron, aluminium, gallium, etc. table respectively and are expected (113Nh), Moscovium (115Mo), Tennessine Hence, it is expected to be a metal, to share some of their chemical and (117Te) and Oganesson (118Og). They solid at room temperature. Its other physical properties with the other complete the 7th period of the periodic properties like boiling point, melting elements in the groups. table and constitute the heaviest elements point, oxidation status, etc. are expected The last of the four new elements, known today. With the discovery of to follow periodic trends. element-118 was fi rst synthesised in these four new chemical elements, the Syntheses of elements 115 and 2002 by a team of Russian and American total number of elements in the periodic 117 were carried out in collaborative scientists at the Joint Institute of Nuclear table has gone up to 118. research between the Joint Institute for Research in Dubna, Russia. It was named The credit for synthesising the four Nuclear Research (Dubna, Russia), ‘Oganesson’ (Og-118) in honour of the new elements goes to scientists from and Lawrence Livermore National Russian physicist Yuri Oganessian, Japan, USA and Russia. During the Laboratory, Tennessee, USA in 2003 leader of the team. It was synthesised by years 2000 to 2012, Japanese scientists and 2010 respectively. The researchers projecting high speed calcium ions on to at RIKEN nuclear research laboratory bombarded targets of Americium-243 a target of californium. It has the highest bombarded a thin target of bismuth and Berkelium-249 with high-speed atomic number and highest mass number ions (83 protons and 126 neutrons) with Calcium-48 ions in a cyclotron. of all known elements. Being highly high-speed zinc ions (30 protons and The elements were named unstable it decays with an estimated half- 40 neutrons) accelerated to 30,000 sq ‘Moscovium’ (Mc- atomic number 115) life of 0.7ms to livermorium (atomic no. km to create a new element of atomic and ‘Tennessine’ (Ts- atomic number 116 and mass no. 290 – another super number 113. The element was later 117) respectively in honour of the cities heavy element). named ‘Nihonium’ (Nh), in honour of Moscow in Russia and Tennessee in Og is a member of the 18th group, their country. USA where the participating laboratories the noble gases, but is signifi cantly more Nh-278 is highly radioactive with are situated. They were able to identify reactive than the other members of the a half-life of only 0.24 millisecond and four isotopes of Moscovium, Mc-287 group. Further, it is thought to be not a decays through a series of alpha particle to Mc-290, all of which decay by gas, but solid at room temperature. emissions to ‘Mendelevium’ (Md - proton alpha emission to various isotopes of Earlier in 2011 the IUPAC had 40 SCIENCE REPORTER August 2017 The last of the four new elements, element-118 was fi rst synthesised in 2002 by a team of Russian and American scientists at the Joint Institute of Nuclear Research in Dubna, Russia. the doubly magic fl erovium-298, which is yet to be synthesised, may have even longer half-life. The other members of the island of stability would be elements with proton number 120 and neutron number 184; proton number 126 and neutron number 184. These elements also have not yet been synthesised. The Russian recognised the discovery of elements moves towards stability through rapid scientist Yuri Oganessian, one of the co- fl erovium (Fl) and livermorium with radioactive decay. synthesisers of fl erovium and after whom proton numbers 114 and 116 respectively; Nevertheless, researchers suspect the element 118 is named, suggests that these are members of the 7th period of the that there can be a group of super heavy there can be a second island around periodic table. With the discovery of the elements that defy this trend to exhibit proton number 164. current four new elements, also of the 7th greater stability and thus longer half- Paul Karol, Chair of the IUPAC period, the 7th period is complete. Now lives. In the electron confi guration of says that even though some attempts there are no blanks in the periodic table. atoms the octet rule states that atoms have been made to synthesise elements What next? Is there an 8th period? become stable when the valence shells with proton numbers 119 and 120, How big does the periodic table get? gain a full complement of valence synthesising the elements on the island of These are some of the interesting electrons, for example the noble gases. stability may prove to be very diffi cult. questions that researchers are trying to Similarly, it is suggested that atomic This is because the nuclei available answer. nucleus is made up of individual shells as starting material do not deliver the A study of the periodic table shows that have different energy levels. Certain necessary sum of neutrons. It is virtually that the stability of the nucleus decreases specifi c numbers of protons and neutrons impossible with the current methods to sharply with the increasing atomic in these energy levels may render the produce such nuclei. He feels newer number beyond the heaviest naturally nucleus particularly stable, creating what technologies are required. occurring element uranium (atomic is known as an “Island of stability”, Since these super heavy elements number 92). For example, isotopes of where the nucleus may exhibit longer are produced so few in numbers at elements with atomic number greater half-life than expected. prohibitively high cost and decay so than 101 decay with half-lives less Glenn Seaborg, who pioneered the fast, one may ask what is the their use? than one day, some with only a few synthesis of transuranium elements, It is true they have no practical use. milliseconds (with the exception of suggested that such ‘magic numbers’ But researchers think that a study of the dubnium – atomic number 105 and mass could be 184 for neutrons and 114, 120, decay of these massive elements may number 268 – which has a half-life of and 126 for protons. One such element give further insight into the forces that about 30 hours). The latest four elements is fl erovium with proton number 114. hold the subatomic particles together confi rm this trend. It is predicted to be near the edge of in the nucleus, the structure of the As more and more protons and the island of stability. Six isotopes of nucleus and the processes involved in neutrons are packed into the nucleus fl erovium have been identifi ed so far, nucleosynthesis. These are fundamental to create heavier and heavier nuclei, ranging in mass number from 284 to questions in nuclear physics. And so the the short range nuclear force which 289 and with increasing half-lives from effort will go on. holds these particles together weakens 2 ms to 2 seconds, the heaviest being towards the edge of the nucleus, the longest lived. It is expected that M.S.S. Murthy, B-104, Terrace Garden Apartments, nd rendering it highly unstable. The nucleus heavier fl erovium isotopes, especially 2 Main Road, BSK IIIrd Stage, Bangalore-85 41 SCIENCE REPORTER August 2017.
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