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=                             Flerovium                              =
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                            Introduction
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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. More recent results show
that flerovium's reaction with gold is similar to that of copernicium,
showing it is very volatile and may even be gaseous at standard
temperature and pressure. Nonetheless, it also seems to show some
metallic properties, consistent with it being the heavier homologue of
lead.

Very little is known about flerovium, as it can only be produced one
atom at a time, either through direct synthesis or through radioactive
decay of even heavier elements, and all known isotopes are
short-lived. Six isotopes of flerovium are known, ranging in mass
number between 284 and 289; the most stable of these,
{{chem2|^{289}Fl}}, has a half-life of ~2.1 seconds, but the
unconfirmed {{chem2|^{290}Fl}} may have a longer half-life of 19
seconds, which would be one of the longest half-lives of any nuclide
in these farthest reaches of the periodic table. Flerovium is
predicted to be near the centre of the theorized island of stability,
and it is expected that heavier flerovium isotopes, especially the
possibly magic {{chem2|^{298}Fl}}, may have even longer half-lives.


Pre-discovery
===============
In the late 1940s to early 1960s, the early days of making heavier and
heavier transuranic elements, it was predicted that since such
elements did not occur naturally, they would have shorter and shorter
spontaneous fission half-lives, until they stopped existing altogether
around element 108 (now called hassium). Initial work in synthesizing
the heavier actinides seemed to confirm this. 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 ^{208}Pb}} was
{{chem2|^{298}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), and the flerovium isotopes in it were
speculated in 1966 to have half-lives over 108 years. These early
predictions fascinated researchers, and led to the first attempt to
make flerovium, in 1968 with the reaction
{{chem2|^{248}Cm(^{40}Ar,xn)}}. No flerovium atoms were detected; this
was thought to be because the compound nucleus {{chem2|^{288}Fl}} 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. Later work suggests the islands of stability
around hassium and flerovium occur because these nuclei are
respectively deformed and oblate, which make them resistant to
spontaneous fission, and that the true island of stability for
spherical nuclei occurs at around unbibium-306 (122 protons, 184
neutrons).

In the 1970s and 1980s, theoretical studies debated whether element
114 would be a more volatile metal like lead, or an inert gas.


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 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. This observation was assigned to {{chem2|^{289}Fl}} and was
published in January 1999. 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 {{chem2|^{289m}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 {{chem2|^{290}Fl}} and electron capture to
{{chem2|^{290}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 {{chem2|^{294}Lv}} in a 248Cm(48Ca,2n) reaction,
which would alpha decay to {{chem2|^{290}Fl}}. The RIKEN team reported
possible synthesis of isotopes {{chem2|^{294}Lv}} and
{{chem2|^{290}Fl}} in 2016 in a 248Cm(48Ca,2n) reaction, but the alpha
decay of {{chem2|^{294}Lv}} was missed, alpha decay of
{{chem2|^{290}Fl}} to {{chem2|^{286}Cn}} was observed instead of
electron capture to {{chem2|^{290}Nh}}, and the assignment to
{{chem2|^{294}Lv}} instead of {{chem2|^{293}Lv}} was not certain.

Glenn T. Seaborg, a scientist at Lawrence Berkeley National Laboratory
who had been involved in work to make such superheavy elements, had
said in December 1997 that "one of his longest-lasting and most
cherished dreams was to see one of these magic elements"; he was told
of the synthesis of flerovium by his colleague Albert Ghiorso soon
after its publication in 1999. Ghiorso later recalled:



Seaborg died two months later, on 25 February 1999.

In March 1999, the same team replaced the {{chem2|^{244}Pu}} target
with {{chem2|^{242}Pu}} to make other flerovium isotopes. Two atoms of
flerovium were produced as a result, each alpha-decaying with a
half-life of 5.5 s. They were assigned as {{chem2|^{287}Fl}}. This
activity has not been seen again either, and it is unclear what
nucleus was produced. It is possible that it was an isomer 287mFl or
from electron capture by 287Fl, leading to 287Nh and 283Rg.


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
==========
{{Isotopes summary
|element=flerovium
|reaction ref=
|isotopes=







}}
While the method of chemical characterization of a daughter was
successful for flerovium and livermorium, and the simpler structure of
even-even nuclei made confirmation of oganesson ('Z' = 118)
straightforward, there have been difficulties in establishing the
congruence of decay chains from isotopes with odd protons, odd
neutrons, or both. To get around this problem with hot fusion, the
decay chains from which terminate in spontaneous fission instead of
connecting to known nuclei as cold fusion allows, experiments were
done in Dubna in 2015 to produce lighter isotopes of flerovium by
reaction of 48Ca with 239Pu and 240Pu, particularly 283Fl, 284Fl, and
285Fl; the last had previously been characterized in the
242Pu(48Ca,5n)285Fl reaction at Lawrence Berkeley National Laboratory
in 2010. 285Fl was more clearly characterized, while the new isotope
284Fl was found to undergo immediate spontaneous fission, and 283Fl
was not observed. This lightest isotope may yet conceivably be
produced in the cold fusion reaction 208Pb(76Ge,n)283Fl, which the
team at RIKEN in Japan at one point considered investigating: this
reaction is expected to have a higher cross-section of 200 fb than the
"world record" low of 30 fb for 209Bi(70Zn,n)278Nh, the reaction which
RIKEN used for the official discovery of element 113 (nihonium).
Alternatively, it might be produced in future as a great-granddaughter
of 295120, reachable in the 249Cf(50Ti,4n) reaction. The reaction
239Pu+48Ca has also been suggested as a means to produce 282Fl and
283Fl in the 5n and 4n channels respectively, but so far only the 3n
channel leading to 284Fl has been observed.

The Dubna team repeated their investigation of the 240Pu+48Ca reaction
in 2017, observing three new consistent decay chains of 285Fl, another
decay chain from this nuclide that may pass through some isomeric
states in its daughters, a chain that could be assigned to 287Fl
(likely from 242Pu impurities in the target), and some spontaneous
fissions of which some could be from 284Fl, though other
interpretations including side reactions involving evaporation of
charged particles are also possible. The alpha decay of 284Fl to
spontaneously fissioning 280Cn was finally observed by the Dubna team
in 2024.


Naming
========
Per Mendeleev's nomenclature for unnamed and undiscovered elements,
flerovium is sometimes called 'eka-lead'. In 1979, IUPAC published
recommendations according to which the element was to be called
'ununquadium' (symbol 'Uuq'),
a systematic element name as a placeholder, until the discovery of
the element is confirmed and a permanent name is decided on. Most
scientists in the field called it "element 114", with the symbol of
'E114', '(114)' or '114'.

Per IUPAC recommendations, the discoverer(s) of a new element has the
right to suggest a name.

After IUPAC recognized the discovery of flerovium and livermorium on 1
June 2011, IUPAC asked the discovery team at JINR to suggest permanent
names for the two elements. The Dubna team chose the name 'flerovium'
(symbol Fl),

after Russia's Flerov Laboratory of Nuclear Reactions (FLNR), named
after Soviet physicist Georgy Flyorov (also spelled Flerov); earlier
reports claim the element name was directly proposed to honour
Flyorov.
Mikhail Itkis, the vice-director of JINR, stated: "We would like to
name element 114 after Georgy Flerov - flerovium, and the second
[element 116] - moscovium, not after Moscow, but after Moscow Oblast".
In accordance with the proposal received from the discoverers, IUPAC
officially named flerovium after Flerov Laboratory of Nuclear
Reactions, not after Flyorov himself. Flyorov is known for writing to
Joseph Stalin in April 1942 and pointing out the silence in scientific
journals in the field of nuclear fission in the United States, Great
Britain, and Germany. Flyorov deduced that this research must have
become classified information in those countries. Flyorov's work and
urgings led to the development of the USSR's own atomic bomb project.
Flyorov is also known for the discovery of spontaneous fission with
Konstantin Petrzhak. The naming ceremony for flerovium and livermorium
was held on 24 October 2012 in Moscow.

In a 2015 interview with Oganessian, the host, in preparation to ask a
question, said, "You said you had dreamed to name [an element] after
your teacher Georgy Flyorov." Without letting the host finish,
Oganessian repeatedly said, "I did."


                        Predicted properties
======================================================================
Very few properties of flerovium or its compounds have been measured;
due to its extremely limited and expensive production and the fact
that it decays very quickly. A few singular properties have been
measured, but for the most part, properties of flerovium remain
unknown and only predictions are available.


Nuclear stability and isotopes
================================
The basis of the chemical periodicity in the periodic table is the
electron shell closure at each noble gas (atomic numbers 2, 10, 18,
36, 54, 86, and 118): as any further electrons must enter a new shell
with higher energy, closed-shell electron configurations are markedly
more stable, hence the inertness of noble gases. Protons and neutrons
are also known to form closed nuclear shells, so the same happens at
nucleon shell closures, which happen at specific nucleon numbers often
dubbed "magic numbers". The known magic numbers are 2, 8, 20, 28, 50,
and 82 for protons and neutrons; also 126 for neutrons. Nuclei with
magic proton and neutron numbers, such as helium-4, oxygen-16,
calcium-48, and lead-208, are "doubly magic" and are very stable. This
stability is very important for superheavy elements: with no
stabilization, half-lives would be expected by exponential
extrapolation to be nanoseconds at darmstadtium (element 110), because
the ever-increasing electrostatic repulsion between protons overcomes
the limited-range strong nuclear force that holds nuclei together. The
next closed nucleon shells (magic numbers) are thought to denote the
centre of the long-sought island of stability, where half-lives to
alpha decay and spontaneous fission lengthen again.

Initially, by analogy with neutron magic number 126, the next proton
shell was also expected at element 126, too far beyond the synthesis
capabilities of the mid-20th century to get much theoretical
attention. In 1966, new values for the potential and spin-orbit
interaction in this region of the periodic table contradicted this and
predicted that the next proton shell would instead be at element 114,
and that nuclei in this region would be relatively stable against
spontaneous fission. The expected closed neutron shells in this region
were at neutron number 184 or 196, making 298Fl and 310Fl candidates
for being doubly magic. 1972 estimates predicted a half-life of around
1 year for 298Fl, which was expected to be near an island of stability
centered near 294Ds (with a half-life around 1010 years, comparable to
232Th). After making the first isotopes of elements 112-118 at the
turn of the 21st century, it was found that these neutron-deficient
isotopes were stabilized against fission. In 2008 it was thus
hypothesized that the stabilization against fission of these nuclides
was due to their oblate nuclei, and that a region of oblate nuclei was
centred on 288Fl. Also, new theoretical models showed that the
expected energy gap between the proton orbitals 2f7/2 (filled at
element 114) and 2f5/2 (filled at element 120) was smaller than
expected, so element 114 no longer appeared to be a stable spherical
closed nuclear shell. The next doubly magic nucleus is now expected to
be around 306Ubb, but this nuclide's expected short half-life and low
production cross section make its synthesis challenging. Still, the
island of stability is expected to exist in this region, and nearer
its centre (which has not been approached closely enough yet) some
nuclides, such as 291Mc and its alpha- and beta-decay daughters, may
be found to decay by positron emission or electron capture and thus
move into the centre of the island. Due to the expected high fission
barriers, any nucleus in this island of stability would decay
exclusively by alpha decay and perhaps some electron capture and beta
decay, both of which would bring the nuclei closer to the
beta-stability line where the island is expected to be. Electron
capture is needed to reach the island, which is problematic because it
is not certain that electron capture is a major decay mode in this
region of the chart of nuclides.

Experiments were done in 2000-2004 at Flerov Laboratory of Nuclear
Reactions in Dubna studying the fission properties of the compound
nucleus 292Fl by bombarding 244Pu with accelerated 48Ca ions. A
compound nucleus is a loose combination of nucleons that have not yet
arranged themselves into nuclear shells. It has no internal structure
and is held together only by the collision forces between the two
nuclei. Results showed how such nuclei fission mainly by expelling
doubly magic or nearly doubly magic fragments such as 40Ca, 132Sn,
208Pb, or 209Bi. It was also found that 48Ca and 58Fe projectiles had
a similar yield for the fusion-fission pathway, suggesting possible
future use of 58Fe projectiles in making superheavy elements.
It has also been suggested that a neutron-rich flerovium isotope can
be formed by quasifission (partial fusion followed by fission) of a
massive nucleus. Recently it has been shown that multi-nucleon
transfer reactions in collisions of actinide nuclei (such as uranium
and curium) might be used to make neutron-rich superheavy nuclei in
the island of stability,
though production of neutron-rich nobelium or seaborgium is more
likely.

Theoretical estimates of alpha decay half-lives of flerovium isotopes,
support the experimental data.


The fission-survived isotope 298Fl, long expected to be doubly magic,
is predicted to have alpha decay half-life ~17 days.

Making 298Fl directly by a fusion-evaporation pathway is currently
impossible: no known combination of target and stable projectile can
give 184 neutrons for the compound nucleus, and radioactive
projectiles such as 50Ca (half-life 14 s) cannot yet be used in the
needed quantity and intensity. One possibility for making the
theorized long-lived nuclei of copernicium (291Cn and 293Cn) and
flerovium near the middle of the island, is using even heavier targets
such as 250Cm, 249Bk, 251Cf, and 254Es, that when fused with 48Ca
would yield isotopes such as 291Mc and 291Fl (as decay products of
299Uue, 295Ts, and 295Lv), which may have just enough neutrons to
alpha decay to nuclides close enough to the centre of the island to
possibly undergo electron capture and move inward to the centre.
However, reaction cross sections would be small and little is yet
known about the decay properties of superheavies near the
beta-stability line. This may be the current best hope to synthesize
nuclei in the island of stability, but it is speculative and may or
may not work in practice. Another possibility is to use controlled
nuclear explosions to get the high neutron flux needed to make
macroscopic amounts of such isotopes. This would mimic the r-process
where the actinides were first produced in nature and the gap of
instability after polonium bypassed, as it would bypass the gaps of
instability at 258-260Fm and at mass number 275 (atomic numbers 104 to
108). Some such isotopes (especially 291Cn and 293Cn) may even have
been synthesized in nature, but would decay far too quickly (with
half-lives of only thousands of years) and be produced in far too
small quantities (~10−12 the abundance of lead) to be detectable today
outside cosmic rays.


Atomic and physical
=====================
Flerovium is in group 14 in the periodic table, below carbon, silicon,
germanium, tin, and lead. Every previous group 14 element has 4
electrons in its valence shell, hence valence electron configuration
ns2np2. For flerovium, the trend will continue and the valence
electron configuration is predicted as 7s27p2; flerovium will be
similar to its lighter congeners in many ways. Differences are likely
to arise; a large contributor is spin-orbit (SO) interaction--mutual
interaction between the electrons' motion and spin. It is especially
strong in superheavy elements, because the electrons move faster than
in lighter atoms, at speeds comparable to the speed of light. For
flerovium, it lowers the 7s and the 7p electron energy levels
(stabilizing the corresponding electrons), but two of the 7p electron
energy levels are stabilized more than the other four.
The stabilization of the 7s electrons is called the inert pair
effect, and the effect "tearing" the 7p subshell into the more and
less stabilized parts is called subshell splitting. Computational
chemists see the split as a change of the second (azimuthal) quantum
number  from 1 to  and  for the more stabilized and less stabilized
parts of the 7p subshell, respectively. For many theoretical purposes,
the valence electron configuration may be represented to reflect the
7p subshell split as 7s7p. These effects cause flerovium's chemistry
to be somewhat different from that of its lighter neighbours.

Because the spin-orbit splitting of the 7p subshell is very large in
flerovium, and both of flerovium's filled orbitals in the 7th shell
are stabilized relativistically; the valence electron configuration of
flerovium may be considered to have a completely filled shell. Its
first ionization energy of 8.539 eVpar should be the second-highest in
group 14. The 6d electron levels are also destabilized, leading to
some early speculations that they may be chemically active, though
newer work suggests this is unlikely. Because the first ionization
energy is higher than in silicon and germanium, though still lower
than in carbon, it has been suggested that flerovium could be classed
as a metalloid.

Flerovium's closed-shell electron configuration means metallic bonding
in metallic flerovium is weaker than in the elements before and after;
so flerovium is expected to have a low boiling point, and has recently
been suggested to be possibly a gaseous metal, similar to predictions
for copernicium, which also has a closed-shell electron configuration.
Flerovium's melting and boiling points were predicted in the 1970s to
be around 70 and 150 °C, significantly lower than for the lighter
group 14 elements (lead has 327 and 1749 °C), and continuing the trend
of decreasing boiling points down the group. Earlier studies predicted
a boiling point of ~1000 °C or 2840 °C, but this is now considered
unlikely because of the expected weak metallic bonding and that group
trends would expect flerovium to have low sublimation enthalpy.
Preliminary 2021 calculations predicted that flerovium should have
melting point −73 °C (lower than mercury at −39 °C and copernicium,
predicted 10 ± 11 °C) and boiling point 107 °C, which would make it a
liquid metal. Like mercury, radon, and copernicium, but not lead and
oganesson (eka-radon), flerovium is calculated to have no electron
affinity.

A 2010 study published calculations predicting a hexagonal
close-packed crystal structure for flerovium due to spin-orbit
coupling effects, and a density of 9.928 g/cm3, though this was noted
to be probably slightly too low. Newer calculations published in 2017
expected flerovium to crystallize in face-centred cubic crystal
structure like its lighter congener lead, and calculations published
in 2022 predicted a density of 11.4 ± 0.3 g/cm3, similar to lead
(11.34 g/cm3). These calculations found that the face-centred cubic
and hexagonal close-packed structures should have nearly the same
energy, a phenomenon reminiscent of the noble gases. These
calculations predict that hexagonal close-packed flerovium should be a
semiconductor, with a band gap of 0.8 ± 0.3 eV. (Copernicium is also
predicted to be a semiconductor.) These calculations predict that the
cohesive energy of flerovium should be around −0.5 ± 0.1 eV; this is
similar to that predicted for oganesson (−0.45 eV), larger than that
predicted for copernicium (−0.38 eV), but smaller than that of mercury
(−0.79 eV). The melting point was calculated as 284 ± 50 K (11 ± 50
°C), so that flerovium is probably a liquid at room temperature,
although the boiling point was not determined.

The electron of a hydrogen-like flerovium ion (Fl113+; remove all but
one electron) is expected to move so fast that its mass is 1.79 times
that of a stationary electron, due to relativistic effects. (The
figures for hydrogen-like lead and tin are expected to be 1.25 and
1.073 respectively.) Flerovium would form weaker metal-metal bonds
than lead and would be adsorbed less on surfaces.


Chemical
==========
Flerovium is the heaviest known member of group 14, below lead, and is
projected to be the second member of the 7p series of elements.
Nihonium and flerovium are expected to form a very short subperiod
corresponding to the filling of the 7p1/2 orbital, coming between the
filling of the 6d5/2 and 7p3/2 subshells. Their chemical behaviour is
expected to be very distinctive: nihonium's homology to thallium has
been called "doubtful" by computational chemists, while flerovium's to
lead has been called only "formal".

The first five group 14 members show a +4 oxidation state and the
latter members have increasingly prominent +2 chemistry due to onset
of the inert pair effect. For tin, the +2 and +4 states are similar in
stability, and lead(II) is the most stable of all the chemically
well-understood +2 oxidation states in group 14. The 7s orbitals are
very highly stabilized in flerovium, so a very large sp3 orbital
hybridization is needed to achieve a +4 oxidation state, so flerovium
is expected to be even more stable than lead in its strongly
predominant +2 oxidation state and its +4 oxidation state should be
highly unstable. For example, the dioxide (FlO2) is expected to be
highly unstable to decomposition into its constituent elements (and
would not be formed by direct reaction of flerovium with oxygen), and
flerovane (FlH4), which should have Fl-H bond lengths of 1.787 Å and
would be the heaviest homologue of methane (the lighter compounds
include silane, germane and stannane), is predicted to be more
thermodynamically unstable than plumbane, spontaneously decomposing to
flerovium(II) hydride (FlH2) and H2. The tetrafluoride FlF4 would have
bonding mostly due to 'sd' hybridizations rather than 'sp'3
hybridizations, and its decomposition to the difluoride and fluorine
gas would be exothermic. The other tetrahalides (for example, FlCl4 is
destabilized by about 400 kJ/mol) decompose similarly. The
corresponding polyfluoride anion  should be unstable to hydrolysis in
aqueous solution, and flerovium(II) polyhalide anions such as  and
are predicted to form preferentially in solutions. The 'sd'
hybridizations were suggested in early calculations, as flerovium's 7s
and 6d electrons share about the same energy, which would allow a
volatile hexafluoride to form, but later calculations do not confirm
this possibility. In general, spin-orbit contraction of the 7p1/2
orbital should lead to smaller bond lengths and larger bond angles:
this has been theoretically confirmed in FlH2. Still, even FlH2 should
be relativistically destabilized by 2.6 eV to below Fl+H2; the large
spin-orbit effects also break down the usual singlet-triplet divide in
the group 14 dihydrides. FlF2 and FlCl2 are predicted to be more
stable than FlH2.

Due to relativistic stabilization of flerovium's 7s27p valence
electron configuration, the 0 oxidation state should also be more
stable for flerovium than for lead, as the 7p1/2 electrons begin to
also have a mild inert pair effect: this stabilization of the neutral
state may bring about some similarities between the behavior of
flerovium and the noble gas radon. Due to flerovium's expected
relative inertness, diatomic compounds FlH and FlF should have lower
energies of dissociation than the corresponding lead compounds PbH and
PbF. Flerovium(IV) should be even more electronegative than lead(IV);
lead(IV) has electronegativity 2.33 on the Pauling scale, though the
lead(II) value is only 1.87. Flerovium could be a noble metal.

Flerovium(II) should be more stable than lead(II), and halides FlX+,
FlX2, , and  (X = Cl, Br, I) are expected to form readily. The
fluorides would undergo strong hydrolysis in aqueous solution. All
flerovium dihalides are expected to be stable; the difluoride being
water-soluble. Spin-orbit effects would destabilize the dihydride
(FlH2) by almost 2.6 eVpar. In aqueous solution, the oxyanion
flerovite () would also form, analogous to plumbite. Flerovium(II)
sulfate (FlSO4) and sulfide (FlS) should be very insoluble in water,
and flerovium(II) acetate (Fl(C2H3O2)2) and nitrate (Fl(NO3)2) should
be quite water-soluble. The standard electrode potential for reduction
of Fl2+ ion to metallic flerovium is estimated to be around +0.9 V,
confirming the increased stability of flerovium in the neutral state.
In general, due to relativistic stabilization of the 7p1/2 spinor,
Fl2+ is expected to have properties intermediate between those of Hg2+
or Cd2+ and its lighter congener Pb2+.


                       Experimental chemistry
======================================================================
Flerovium is currently the last element whose chemistry has been
experimentally investigated, though studies so far are not conclusive.
Two experiments were done in April-May 2007 in a joint FLNR-PSI
collaboration to study copernicium chemistry. The first experiment
used the reaction 242Pu(48Ca,3n)287Fl; and the second,
244Pu(48Ca,4n)288Fl: these reactions give short-lived flerovium
isotopes whose copernicium daughters would then be studied. Adsorption
properties of the resultant atoms on a gold surface were compared to
those of radon, as it was then expected that copernicium's full-shell
electron configuration would lead to noble-gas like behavior. Noble
gases interact with metal surfaces very weakly, which is
uncharacteristic of metals.

The first experiment found 3 atoms of 283Cn but seemingly also 1 atom
of 287Fl. This was a surprise; transport time for the product atoms is
~2 s, so the flerovium should have decayed to copernicium before
adsorption. In the second reaction, 2 atoms of 288Fl and possibly 1 of
289Fl were seen. Two of the three atoms showed adsorption
characteristics associated with a volatile, noble-gas-like element,
which has been suggested but is not predicted by more recent
calculations. These experiments gave independent confirmation for the
discovery of copernicium, flerovium, and livermorium via comparison
with published decay data. Further experiments in 2008 to confirm this
important result detected 1 atom of 289Fl, and supported previous data
showing flerovium had a noble-gas-like interaction with gold.

Empirical support for a noble-gas-like flerovium soon weakened. In
2009 and 2010, the FLNR-PSI collaboration synthesized more flerovium
to follow up their 2007 and 2008 studies. In particular, the first
three flerovium atoms made in the 2010 study suggested again a
noble-gas-like character, but the complete set taken together resulted
in a more ambiguous interpretation, unusual for a metal in the carbon
group but not fully like a noble gas in character. In their paper, the
scientists refrained from calling flerovium's chemical properties
"close to those of noble gases", as had previously been done in the
2008 study. Flerovium's volatility was again measured through
interactions with a gold surface, and provided indications that the
volatility of flerovium was comparable to that of mercury, astatine,
and the simultaneously investigated copernicium, which had been shown
in the study to be a very volatile noble metal, conforming to its
being the heaviest known group 12 element. Still, it was pointed out
that this volatile behavior was not expected for a usual group 14
metal.

In experiments in 2012 at GSI, flerovium's chemistry was found to be
more metallic than noble-gas-like. Jens Volker Kratz and Christoph
Düllmann specifically named copernicium and flerovium as being in a
new category of "volatile metals"; Kratz even speculated that they
might be gases at standard temperature and pressure. These "volatile
metals", as a category, were expected to fall between normal metals
and noble gases in terms of adsorption properties. Contrary to the
2009 and 2010 results, it was shown in the 2012 experiments that the
interactions of flerovium and copernicium respectively with gold were
about equal. Further studies showed that flerovium was more reactive
than copernicium, in contradiction to previous experiments and
predictions.

In a 2014 paper detailing the experimental results of the chemical
characterization of flerovium, the GSI group wrote: "[flerovium] is
the least reactive element in the group, but still a metal."
Nevertheless, in a 2016 conference about chemistry and physics of
heavy and superheavy elements, Alexander Yakushev and Robert Eichler,
two scientists who had been active at GSI and FLNR in determining
flerovium's chemistry, still urged caution based on the
inconsistencies of the various experiments previously listed, noting
that the question of whether flerovium was a metal or a noble gas was
still open with the known evidence: one study suggested a weak
noble-gas-like interaction between flerovium and gold, while the other
suggested a stronger metallic interaction. The longer-lived isotope
{{chem2|^{289}Fl}} has been considered of interest for future
radiochemical studies.

Experiments published in 2022 suggest that flerovium is a metal,
exhibiting lower reactivity towards gold than mercury, but higher
reactivity than radon. The experiments could not identify if the
adsorption was due to elemental flerovium (considered more likely), or
if it was due to a flerovium compound such as FlO that was more
reactive towards gold than elemental flerovium, but both scenarios
involve flerovium forming chemical bonds.


                              See also
======================================================================
* Island of stability: Flerovium-Unbinilium-Unbihexium
* Isotopes of flerovium
* Extended periodic table


                            Bibliography
======================================================================
*
[http://cms.iopscience.org/ac0c0614-0d60-11e7-9a47-19ee90157113/030001.pdf?guest=true
pp. 030001-1-030001-17],
[http://cms.iopscience.org/b3dbafd9-0d60-11e7-9a47-19ee90157113/030001_Table1.pdf?guest=true
pp. 030001-18-030001-138, Table I. The NUBASE2016 table of nuclear and
decay properties]
*
*
*
*


*
:*
:*
:*


                           External links
======================================================================
*
[https://web.archive.org/web/20080723144358/http://www.cerncourier.com/main/article/39/7/18
'CERN Courier' - First postcard from the island of nuclear stability]
*
[https://web.archive.org/web/20081205080201/http://www.cerncourier.com/main/article/41/8/17
'CERN Courier' - Second postcard from the island of stability]


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