in your element One flerovium atom at a time The chemistry of element 114 seems to be in reach, yet Peter Schwerdtfeger cautions that we should expect the unexpected from this young element, which is so different to its lighter counterparts. he last primordial element in the cutting edge of current chemical technology periodic table — with a lifetime requires some knowledge of their chemical Tcomparable to the age of our Earth — behaviour. The use of modern relativistic is plutonium, which is found only in trace quantum chemical methods that deal amounts in a mineral named bastnasite. with the Dirac instead of the Schrödinger All elements beyond 94Pu have been equation offers an ideal tool for probing produced in nuclear fusion reactions in a flerovium’s reactivity. few laboratories around the world, most It was the late Kenneth Pitzer who recently from an ongoing Dubna–Livermore pointed out as early as 1975 that strong collaboration that led in 2004 to the relativistic effects could lead to an electronic discovery of flerovium. shell closure in element 114. Large spin- Four isotopes of element 114, with orbit coupling effects sufficiently separate atomic numbers from 286 to 289, have been the 7p1/2 from the 7p3/2 shells (by more produced at a heavy-ion cyclotron from than 300 kJ mol–1), and flerovium adopts a 48 2 2 nuclear fusion reactions between Ca ion 7s (7p1/2) closed-shell configuration. It is beams and targets made of several isotopes therefore predicted to be rather volatile and of plutonium or curium. In 2011, the chemically inert. Pitzer even went as far as International Union of Pure and Applied to suggest that element 114 could be a gas at Chemistry agreed to name element 114 after room temperature in contrast to lead or tin, the Flerov Laboratory of Nuclear Reactions its lighter counterparts in group 14. in Dubna, which itself took the name of It is, however, not always possible to its founder, Georgii Nikolajevich Flerov predict bulk phenomena from simple atomic (pictured), a prominent Russian nuclear / ALAMY © RIA NOVOSTI properties. Recent solid-state calculations physicist and co-discoverer of spontaneous in our group gave some surprising results. nuclear fission. Flerovium takes its place stability to the element. For more than four Atoms in bulk metallic flerovium are only in the periodic table as the last member of decades, shell closure has been predicted weakly bound, less than in mercury, but group 14, which begins with carbon and at Z = 114 for protons and at N = 184 for more than in xenon (cohesive energies until recently ended with lead. neutrons. However, although most scientists of 50, 75 and 16 kJ mol–1, respectively). This exotic superheavy element has such have long agreed on the number for neutron This suggests that flerovium would be a a high nuclear charge that it can only be shell closure, that for proton shell closure metallic liquid at room temperature, much produced one-atom-at-a-time by fusion depends very much on the model used to like mercury. Moreover the 7s orbitals, over several months — a rather long period determine the underlying nuclear structure. stabilized by relativistic effects, may become of time compared with its nuclear decay, Unlike for the electronic structure, the chemically inert. which is in the range of seconds. Flerovium strong interactions between the nucleons Heinz Gäggeler and co-workers have is exciting in several aspects; in particular, are difficult to model accurately, and shell probed the adsorption of 112Cn and 114Fl on it may help to understand nuclear matter closure has also been predicted at Z = 120, gold surfaces. So far, only three events have in the high proton limit, and in the search 122 or even 126. Accurate measurements been seen that can be assigned to flerovium for the island of stability, with isotopes of of the radioactive decay properties of atoms, suggesting that element 114 behaves high nuclear stability in a certain proton and superheavy elements are therefore required more like a noble, yet still metallic, gas. neutron range. to refine these nuclear models. The most However, the results are not yet conclusive The atomic nucleus consists of proton neutron-rich isotope of flerovium known and confirmation experiments are ongoing. and neutron shells, very much like the at present is 289Fl with 114 protons and 175 What kind of chemistry can flerovium electronic shells we are all familiar with in neutrons, but it still falls short of neutron engage in? Let us expect the unexpected! ❐ chemistry. A completely filled shell would shell closure by 9 neutrons and it is less than have a ‘magic number’ of neutrons and clear how to get them inside the nucleus. PETER SCHWERDTFEGER is at the New protons, which would confer particular Nuclear decay times in the range of Zealand Institute for Advanced Studies seconds are sufficient to perform atom-at- (NZIAS) at Massey University in Auckland, a-time chemistry on superheavy elements, New Zealand. but the design of such experiments at the e-mail: [email protected] Rg Cn 113 Fl 115 Lv 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 636 NATURE CHEMISTRY | VOL 5 | JULY 2013 | www.nature.com/naturechemistry © 2013 Macmillan Publishers Limited. All rights reserved.