Flerovium

Flerovium is a synthetic chemical element; it has symbol Fl and atomic number 114. It is an extremely radioactive, superheavy element, named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna, Russia, where the element was discovered in 1999. The lab's name, in turn, honours Russian physicist Georgy Flyorov ( in Cyrillic, hence the transliteration of "yo" to "e"). IUPAC adopted the name on 30 May 2012. The name and symbol had previously been proposed for element 102 (nobelium) but were not accepted by IUPAC at that time.

It is a transactinide in the p-block of the periodic table. It is in period 7 and is the heaviest known member of the carbon group. Initial chemical studies in 2007–2008 indicated that flerovium was unexpectedly volatile for a group 14 element. But the nuclear shell model, introduced in 1949 and extensively developed in the late 1960s by William Myers and Władysław Świątecki, stated that protons and neutrons form shells within a nucleus, analogous to electron shells. Noble gases are unreactive due to a full electron shell; similarly, it was theorized that elements with full nuclear shells – those having "magic" numbers of protons or neutrons – would be stabilized against decay. A doubly magic isotope, with magic numbers of both protons and neutrons, would be especially stabilized. Heiner Meldner calculated in 1965 that the next doubly magic isotope after Pb was Fl with 114 protons and 184 neutrons, which would be the centre of an "island of stability". This island of stability, supposedly from copernicium (Z = 112) to oganesson (Z = 118), would come after a long "sea of instability" from mendelevium (Z = 101) to roentgenium (Z = 111), These early predictions fascinated researchers, and led to the first attempt to make flerovium, in 1968 with the reaction . No flerovium atoms were detected; this was thought to be because the compound nucleus only has 174 neutrons instead of the supposed magic 184, and this would have significant impact on the reaction cross section (yield) and half-lives of nuclei produced. It was then 30 more years before flerovium was first made.

First signs

The first sign of flerovium was found in December 1998 by a team of scientists at Joint Institute for Nuclear Research (JINR), Dubna, Russia, led by Armenian nuclear scientist Yuri Oganessian, who bombarded a target of plutonium-244 with accelerated nuclei of calcium-48:

: + → * → + 2

This reaction had been tried before, without success; for this 1998 attempt, JINR had upgraded all of its equipment to detect and separate the produced atoms better and bombard the target more intensely. One atom of flerovium, alpha decaying with lifetime 30.4 s, was detected. The decay energy measured was 9.71 MeV, giving an expected half-life of 2–23 s. The experiment was later repeated, but an isotope with these decay properties was never observed again, so the exact identity of this activity is unknown. It may have been due to the isomer Fl, but because the presence of a whole series of longer-lived isomers in its decay chain would be rather doubtful, the most likely assignment of this chain is to the 2n channel leading to Fl and electron capture to Nh. This fits well with the systematics and trends of flerovium isotopes, and is consistent with the low beam energy chosen for that experiment, though further confirmation would be desirable via synthesis of Lv in a Cm(Ca,2n) reaction, which would alpha decay to Fl.|Albert Ghiorso

Seaborg died two months later, on 25 February 1999. This activity has not been seen again either, and it is unclear what nucleus was produced. It is possible that it was an isomer Fl

Confirmed discovery

The now-confirmed discovery of flerovium was made in June 1999 when the Dubna team repeated the first reaction from 1998. This time, two atoms of flerovium were produced; they alpha decayed with half-life 2.6 s, different from the 1998 result. This activity was initially assigned to ²⁸⁸Fl in error, due to the confusion regarding the previous observations that were assumed to come from ²⁸⁹Fl. Further work in December 2002 finally allowed a positive reassignment of the June 1999 atoms to ²⁸⁹Fl.

In May 2009, the Joint Working Party (JWP) of IUPAC published a report on the discovery of copernicium in which they acknowledged discovery of the isotope ²⁸³Cn. This implied the discovery of flerovium, from the acknowledgement of the data for the synthesis of ²⁸⁷Fl and ²⁹¹Lv, which decay to ²⁸³Cn. The discovery of flerovium-286 and -287 was confirmed in January 2009 at Berkeley. This was followed by confirmation of flerovium-288 and -289 in July 2009 at Gesellschaft für Schwerionenforschung (GSI) in Germany. In 2011, IUPAC evaluated the Dubna team's 1999–2007 experiments. They found the early data inconclusive, but accepted the results of 2004–2007 as flerovium, and the element was officially recognized as having been discovered.

Isotopes