Flerovium – facts and properties

Position in the periodic table

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Occurrence and extraction

Flerovium does not occur in nature. Not one known isotope is stable. For the longest-lived secure isotope, flerovium-289, the literature quotes a half-life of about two seconds, but the figure rests on few atoms.

In December 1998 a group around Yuri Oganessian at the Flerov Laboratory of the Joint Institute for Nuclear Research in Dubna saw the first atom, made by bombarding plutonium-244 with calcium-48. Publication followed in 1999. Only in 2011 was the discovery credited to Dubna and the Lawrence Livermore National Laboratory, and then on the basis of later experiments.

The method that took Dubna to flerovium and the four heavier elements is called hot fusion. Cold fusion, used in Darmstadt and Japan with lead or bismuth targets, reached its limit at nihonium because the yield fell too steeply. In hot fusion one instead bombards an actinide target, such as plutonium-244, with calcium-48. That isotope is especially favourable: it has 20 protons and 28 neutrons, both magic numbers, which makes it a tightly bound, neutron-rich nucleus. When it fuses with a plutonium nucleus of 94 protons, the result has 114 protons and sheds its surplus energy by boiling off three or four neutrons. Of 244 plus 48 particles, 289 remain after three neutrons: flerovium-289.

The same sum leads from americium (95 protons) to moscovium, from curium (96) to livermorium, from berkelium (97) to tennessine and from californium (98) to oganesson. Calcium-48 makes up barely two parts in a thousand of natural calcium and has to be enriched. The actinide target material comes mainly from US reactors such as the one at Oak Ridge. Often only one atom appears in days to weeks of beam time.

The name honours the Flerov Laboratory of Nuclear Reactions, which is named after its founder Georgy Flerov (1913–1990). In 1940 he and Konstantin Petrzhak discovered the spontaneous fission of uranium.

Properties and reactions

Flerovium is in period 7 and group 14, below lead, with tin, germanium, silicon and carbon above. The predicted electron configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p², giving 4 valence electrons: two in the 7s and two in the 7p orbital. The atomic mass entry is 289 u, the mass number of flerovium-289. There are no measured values for melting point, boiling point or density.

For a long time a nucleus with 114 protons and 184 neutrons was expected to have an especially stable shell, and with it the island of stability, a hoped-for region of longer-lived nuclei. The known isotopes still lack a few neutrons and so do not yet sit on that island. Where exactly the shell lies is open, since newer calculations also name other proton numbers.

Group membership suggests a metal like lead. Relativistic effects change the picture, because they split the 7p level. In flerovium the two 7p electrons fill the lower, more tightly bound sublevel completely, so the atom acts like one with a closed shell. It should therefore bind only weakly and be easily volatile, perhaps even noble-gas-like. Calculated melting and boiling points scatter widely, from a gas to an easily melting metal.

Gas-phase experiments with single atoms on gold have tested this. First results from Dubna spoke for a very weak interaction, that is, noble-gas-like behaviour. Later measurements at GSI in Darmstadt found a weak but detectable bond and made flerovium look like a very volatile metal. The interpretation remains disputed, partly because only a few atoms were ever observed. The single atoms pose no danger.

Research and synthesis

Flerovium is studied in basic research only and has no application. At the centre are the island of stability and the question whether the order by groups still holds for atoms so strongly shaped by relativity.

For nuclear physicists flerovium is a testing ground for models. The isotopes and their decay chains show how stability grows with neutron number.

Quick question

What is the atomic number of flerovium (Fl)?

FAQ