in your element Mendelevium 101 The frst element to be identifed one atom at a time was named after the main architect of the modern periodic table. This seemingly straightforward etymological choice illustrates how scientifc recognition can eclipse geopolitical tensions, says Anne Pichon.

year to prepare a target, a week to the Arctic Ocean and crater on the dark side make a new element, a couple of hours of the moon. to detect it: the creation of element 101 Today, 17 isotopes of mendelevium are A 258 was truly a race against time. By the middle of known; 101, with its half-life of 51.5 days, the 20th century, the University of California is the least unstable. Relatively large Radiation Laboratory, in Berkeley, was no quantities of lighter transuraniums can stranger to the synthesis of transuranium be formed in nuclear reactors by neutron elements. Neptunium was discovered there in capture followed by β– decay (conversion of 1940, as was plutonium. Investigations into a neutron into a proton), but this process nuclear processes as part of the Manhattan cannot produce mendelevium because Project, analyses of the fallout from nuclear- of the ‘fermium wall’ — isotopes of weapon tests, and experiments using Ernest element 100 simply decay too quickly. Lawrence’s cyclotron had led Berkeley Statue of Dmitri Mendeleev in St Petersburg. The resulting scarcity means that scientists to discover elements 95 to 100, Credit: Anton Veselov / Alamy Stock Photo mendelevium has undergone few all between 1944 and 1952. These heavy experimental investigations and has no atoms could be produced in a cyclotron by practical use. It is known to adopt the +3 bombarding actinide targets with neutrons predicted the chemical properties of yet- and +2 oxidation states in solution, and the or α-particles. unknown elements using their position in fluoride and hydroxide species MdF3 and In 1955, Glenn Seaborg, Albert Ghiorso his classification system. The same principle Md(OH)3 have been prepared together with and colleagues created 256101 by firing had guided the discovery of the transuranium their lanthanide homologues. Using one- α-particles at 25399 nuclei (now known as elements; indeed, these elements eluded atom-at-a-time techniques and relativistic einsteinium). Coming on the heels of several identification until Seaborg correctly placed calculations, the ionization potential of 251Md synthetic successes, it may seem to have been the actinide series on the periodic table. has also recently been measured5, along with a fairly simple affair, but it wasn't. It took a During the Cold War, however, honouring those of 249Fm,257No and 256Lr. The trend whole year to prepare enough 25399 to make a a Russian scientist in this manner was found for these actinides mirrors that of target — which then decayed within about a controversial. The name ‘mendelevium’ was the late lanthanides. week. The team pioneered a ‘recoil’ technique carefully considered and ran past the US Back in Berkeley, as the elemental that enabled target reuse, by providing the government before being proposed to, and synthesis story continued to unfold, other nuclei created with enough energy to leave ratified by, IUPAC in 1955 (with the symbol protagonists joined Mendeleev on the the target and enter a ‘catcher’ foil. This was Mv, changed to Md two years later). periodic table: elements 103 and 106 now also an extremely low-yield synthesis: hours Mendeleev’s chemical legacy spans well go by the respective names of lawrencium of bombardment produced a handful of beyond his crucial contribution to the and seaborgium. ❐ atoms, which soon vanished (the half-life development of the periodic table, even of 256101 is just 77 minutes). though some of his theories didn’t withstand Anne Pichon A video from 1955 that casts some of the test of time quite so well; he was reluctant Senior Editor at Nature Chemistry. the team conveys the excitement of this to accept the existence of the electron, Twitter : @AnneNotInTokyo synthesis1. They raced from the cyclotron focusing instead on understanding the e-mail: [email protected] to the lab to analyse their sample, through universal ‘ether’3. Accounts of his life portray chemical separations and by recording a man with socio-economic interests who Published online: 21 February 2019 the radioactive decay of single atoms. On passionately pursued many lines of enquiry. https://doi.org/10.1038/s41557-019-0227-8 discovery day, 17 atoms of 256101 had been He foresaw the chemical value of petroleum, created. It was the first identification of a contributed to setting up women’s courses at References new element one atom at a time, yet also the St Petersburg University, and rode in a hot- 1. Te Element Hunters: Te Discovery of Mendelevium. Voices of 2 the Manhattan Project https://go.nature.com/2G8kvY8 (2017). last to use chemical processes . air balloon, rather inadvertently on his own, 2. Hofman, D. J. Radioanal. Nucl. Chem. 291, 5–11 (2012). The new element was named after Dmitri to study a solar eclipse4. It thus seems fitting 3. Nature 75, 371–373 (1946). Mendeleev, specifically because he had that beyond the chemical chart — sometimes 4. Spitsyn, V. I. & Katz, J. J. (eds) Proceedings of the Moscow Symposium on the Chemistry of Transuranium Elements referred to as ‘Mendeleev’s table’ — and its (Elsevier, Amsterdam, 1976). 101th tile, he also has an eponymous ridge in 5. Sato, T. K. et al. J. Am. Chem. Soc. 140, 14609–14613 (2018). Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og

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