Ununbium is a synthetic radioactive
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
with the
temporaryA systematic element name is the temporary name and symbol assigned to newly synthesized and not yet synthesized chemical elements. In chemistry, a transuranic element receives a permanent trivial name and symbol only after its synthesis has been confirmed. In some cases, this has been a...
symbol
Uub and
atomic numberIn chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
112. "Ununbium" is a IUPAC
systematic element nameA systematic element name is the temporary name and symbol assigned to newly synthesized and not yet synthesized chemical elements. In chemistry, a transuranic element receives a permanent trivial name and symbol only after its synthesis has been confirmed. In some cases, this has been a...
, used until the element receives an accepted name.
Ununbium was first created by the
GSIThe GSI Helmholtz Centre for Heavy Ion Research GmbH in the Arheilgen suburb of Darmstadt, Germany is a federally and state co-funded heavy ion research center. The current director of GSI is Horst Stöcker who succeeded Walter F...
in 1996, who have now proposed the permanent name
copernicium and the symbol
Cn. This name is expected to be officially endorsed by IUPAC in January 2010, after six months for discussion. Element 112 is currently the
highest-numbered elementIn chemistry, transuranium elements are the chemical elements with atomic numbers greater than 92...
to be officially recognised by IUPAC.
The most stable isotope discovered to date is
285Uub with a
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
of ~30 s. In total, about 75 atoms of ununbium have been detected using various nuclear reactions. An unconfirmed isotope,
285bUub, has a possible
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
of ~9 minutes, and would be one of the longest-lived superheavy isotopes known to date.
Recent experiments strongly suggest that ununbium behaves as a typical member of group 12, demonstrating properties consistent with a volatile metal.
Official discovery
Ununbium was first created on February 9, 1996 at the
Gesellschaft für SchwerionenforschungThe GSI Helmholtz Centre for Heavy Ion Research GmbH in the Arheilgen suburb of Darmstadt, Germany is a federally and state co-funded heavy ion research center. The current director of GSI is Horst Stöcker who succeeded Walter F...
(GSI) in
DarmstadtDarmstadt is a city in the Bundesland of Hesse in Germany, located in the southern part of the Rhine Main Area.The city of Darmstadt was founded by the Counts of Katzenelnbogen in 1330, though settlement in the area is known to have been present as early as the late 11th century...
,
GermanyGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
by Sigurd Hofmann,
Victor NinovVictor Ninov is a former researcher in the nuclear chemistry group at Lawrence Berkeley National Laboratory who was alleged to have fabricated the evidence used to claim the creation of ununoctium and ununhexium ....
et al. This element was created by firing accelerated
zincZinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
-70 nuclei at a target made of
leadLead is a main-group element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air...
-208 nuclei in a heavy ion accelerator. A single atom (the second has subsequently been dismissed) of ununbium was produced with a mass number of 277.
- Pb + Zn → Uub → Uub + n
In May 2000, the GSI successfully repeated the experiment to synthesise a further atom of Uub-277.
This reaction was repeated at
RIKENis a large natural sciences research institute in Japan. Founded in 1917, it now has approximately 3000 scientists on seven campuses across Japan, the main one in Wako, just outside Tokyo...
using the GARIS set-up in 2004 to synthesise two further atoms and confirm the decay data reported by the GSI team.
The IUPAC/IUPAP Joint Working Party (JWP) assessed the claim of discovery by the GSI team in 2001 and 2003. In both cases, they found that there was insufficient evidence to support their claim. This was primarily related to the contradicting decay data for the known isotope
261Rf. However, between 2001-2005, the GSI team studied the reaction
248Cm(
26Mg,5n)
269Hs, and were able to confirm the decay data for
269Hs and
261Rf. It was found that the existing data on
261Rf was for an isomer,
now designated
261a Rf.
In May 2009, the JWP reported on the claims of discovery of element 112 again and officially recognised the GSI team as the discoverers of element 112. This decision was based on recent confirmation of the decay properties of daughter nuclei as well as the confirmatory experiments at RIKEN.
Naming
The element with Z=112 is historically known as eka-mercury. Ununbium is a temporary IUPAC
systematic element nameA systematic element name is the temporary name and symbol assigned to newly synthesized and not yet synthesized chemical elements. In chemistry, a transuranic element receives a permanent trivial name and symbol only after its synthesis has been confirmed. In some cases, this has been a...
. Research scientists usually refer to the element simply as element 112 (or just E112).
After acknowledging their discovery, the IUPAC has asked the discovery team at GSI to suggest a permanent name for ununbium. On the 14th July 2009, they proposed
copernicium with the element symbol
Cp, after
Nicolaus CopernicusNicolaus Copernicus was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe...
"to honor an outstanding scientist, who changed our view of the world." IUPAC has not yet officially recognized this name, pending the results of a six month discussion period among the scientific community.
Some news articles have referred to the suggested name as "
copernicum" in error. However, the IUPAC only allows the suffix -ium for new elements. Alternative spellings have been suggested to Hofmann, namely "
copernicum", "
copernium", and "
kopernikium" (
Kp), and Hofmann has said that the team had discussed the possibility of "copernicum" or "kopernikum", but that they had agreed on "
copernicium" in order to comply with current IUPAC rules.
However, it has been pointed out that the symbol
Cp was previously associated with the name
cassiopeium (cassiopium), now known as
lutetiumLutetium is a chemical element with the symbol Lu and atomic number 71. It is in the d-block of the periodic table, not the f-block, but the IUPAC classifies it as a lanthanide. It is one of the elements that traditionally was included in the classification, "rare earths"...
(Lu). Furthermore, the symbol
Cp is also used in inorganic chemistry to denote the ligand
cyclopentadieneCyclopentadiene is a chemical compound with the formula C5H6. This colorless liquid organic chemical has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels-Alder reaction...
. For this reason, the IUPAC has disallowed the use of
Cp as a future symbol and the GSI team has put forward the symbol
Cn as an alternative proposal.
Target-projectile combinations leading to Z=112 compound nuclei
The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=112.
| Target | Projectile | CN | Attempt result |
|---|
| 208Pb |
70Zn |
278112 |
|
| 232Th |
50Ti |
282112 |
|
| 238U |
48Ca |
286112 |
|
| 244Pu |
40Ar |
284112 |
|
| 248Cm |
36S |
284112 |
|
| 249Cf |
30Si |
279112 |
|
Cold fusion
This section deals with the synthesis of nuclei of ununbium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10-20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.
208Pb(70Zn,xn)278-xUub (x=1)
The team at GSI first studied this reaction in 1996 and detected two decay chains of
277Uub.
In a review of the data in 2000, the first decay chain was retracted. In a repeat of the reaction in 2000 they were able to synthesise a further atom. They attempted to measure the 1n excitation function in 2002 but suffered from a failure of the Zn-70 beam.
The unofficial discovery of
277Uub was confirmed in 2004 at
RIKENis a large natural sciences research institute in Japan. Founded in 1917, it now has approximately 3000 scientists on seven campuses across Japan, the main one in Wako, just outside Tokyo...
who detected a further 2 atoms of the isotope and were able to confirm the decay data for the entire chain.
208Pb(68Zn,xn)276-xUub
Following the successful synthesis of
277Uub, the GSI team performed a reaction using a
68Zn projectile in 1997 in an effort to study the effect of
isospinIn physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number...
(neutron richness) on the chemical yield. The experiment was initiated following the discovery of a yield enhancement during the synthesis of
darmstadtiumDarmstadtium , formerly known as ununnilium, is a chemical element with the symbol Ds and atomic number 110. It is placed as the heaviest member of group 10 but a sufficiently stable isotope is not known which would allow chemical experiments to confirm its place. This synthetic element is one of...
isotopes using
62Ni and
64Ni ions. No decay chains of
275Uub were detected leading to a cross section limit of 1.2 pb. However, the revision of the yield for the
70Zn reaction to 0.5 pb does not rule out a similar yield for this reaction.
184W(88Sr,xn)272-xUub
In 1990, after some early indications for the formation of isotopes of element 112 in the irradiation of a tungsten target with multi-GeV protons, a collaboration between GSI and the University of Jerusalem studied the above reaction. They were able to detect some
spontaneous fissionSpontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. It is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 atomic mass units , i.e. elements near ruthenium. In practice, however, spontaneous fission is only energetically...
activity and a 12.5 MeV alpha decay, both of which they tentatively assigned to the radiative capture product
272Uub or the 1n evaporation residue
271Uub. Both the TWG and JWP have concluded that a lot more research is required to confirm these conclusions.
Hot fusion
This section deals with the synthesis of nuclei of ununbium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40-50 MeV, hence "hot"), leading to a reduced probability of survival from fission and quasi-fission. The excited nucleus then decays to the ground state via the emission of 3-5 neutrons. Fusion reactions utilizing
48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30-35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.
238U(48Ca,xn)286-xUub (x=3,4)
In 1998, the team at the Flerov Laboratory of Nuclear Research began a research program using Ca-48 nuclei in "warm" fusion reactions leading to superheavy elements (SHE's).
In March 1998, they claimed to have synthesised the element (2 atoms) in this reaction.
The product,
283Uub, had a claimed half-life of 5 min, decaying by spontaneous fission (SF).
The long lifetime of the product initiated first chemical experiments on the gas phase atomic chemistry of element 112. In 2000, Yuri Yukashev at Dubna repeated the experiment but was unable to observe any
spontaneous fissionSpontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. It is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 atomic mass units , i.e. elements near ruthenium. In practice, however, spontaneous fission is only energetically...
from 5 min activities. The experiment was repeated in 2001 and an accumulation of 8 SF fragments were found in the low temperature section, indicating that ununbium had radon-like properties. However, there is now some serious doubt about the origin of these results.
In order to confirm the synthesis, the reaction was successfully repeated by the same team in Jan 2003, confirming the decay mode and half life. They were also able to calculate an estimate of the mass of the SF activity to ~285 lending support to the assignment.
The team at LBNL entered the debate and performed the reaction in 2002. They were unable to detect any SF activities and calculated a cross section limit of 1.6 pb for the detection of a single event.
The reaction was repeated in 2003-2004 by the team at Dubna using a slightly different set-up, the Dubna Gas Filled Recoil Separator (DGFRS). This time,
283Uub was found to decay by emission of a 9.53 MeV alpha-particle with a half-life of 4 seconds.
282Uub was also observed in the 4n channel.
In 2003, the team at GSI entered the debate and performed a search for the 5 minute SF activity in chemical experiments. Like the Dubna team, they were able to detect 7 SF fragments in the low temperature section. However, these SF events were uncorrelated, suggesting they were not from actual direct SF of element 112 nuclei and raised doubts about the original indications for radon-like properties. After the announcement from Dubna of different decay properties for
283Uub, the GSI team repeated the experiment in September 2004. They were unable to detect any SF events and calculated a cross section limit of ~ 1.6 pb for the detection of one event, not in contradiction with the reported 2.5 pb yield by Dubna.
In May 2005, the GSI performed a physical experiment and identified a single atom of
283Uub decaying by SF with a short lifetime suggesting a previously unknown SF branch.
However, initial work by Dubna had detected several direct SF events but had assumed that the parent alpha decay had been missed. These results indicated that this was not the case.
In 2006, the new decay data on
283Uub was confirmed by a joint PSI-FLNR experiment aimed at probing the chemical properties of ununbium. Two atoms of
283Uub were observed in the decay of the parent
287Uuq nuclei. The experiment indicated that contrary to previous experiments, element 112 behaves as a typical member of group 12, demonstrating properties of a volatile metal.
Finally, the team at GSI successfully repeated their physical experiment in Jan 2007 and detected 3 atoms of
283Uub, confirming both the alpha and SF decay modes.
As such, the 5 min SF activity is still unconfirmed and unidentified. It is possible that it refers to an isomer, namely
283bUub, whose yield is obviously dependent upon the exact production methods.
233U(48Ca,xn)281-xUub
The team at FLNR studied this reaction in 2004. They were unable to detect any atoms of element 112 and calculated a cross section limit of 600 fb. The team concluded that this indicated that the neutron mass number for the compound nucleus had an effect on the yield of evaporation residues.
As a decay product
Element 112 has also been observed as decay products of elements 114, 116, and 118 (see
ununoctiumUnunoctium , also known as eka-radon or element 118, is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. On the periodic table of the elements, it is a p-block element and the last one of the 7th period. Ununoctium is currently...
).
| Evaporation Residue | Observed Uub isotope |
|---|
| 293116, 289114 |
285112 |
| 292116, 288114 |
284112 |
| 291116, 287114 |
283112 |
| 294118, 290116 , 286114 |
282112 |
As an example, in May 2006, the Dubna team (
JINRThe Joint Institute for Nuclear Research, JINR in Dubna, Moscow Oblast , Russia is an international research centre for nuclear sciences, involving around 5500 staff members, 1200 researchers including 1000 Ph.D.s from eighteen member states The Joint Institute for Nuclear Research, JINR in...
) identified
282Uub as a final product in the decay of ununoctium via the
alpha decayAlpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle, and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
sequence:
- → → →
It was found that the final nucleus undergoes
spontaneous fissionSpontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. It is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 atomic mass units , i.e. elements near ruthenium. In practice, however, spontaneous fission is only energetically...
.
281Uub
In the claimed synthesis of
293Uuo in 1999 (see
ununoctiumUnunoctium , also known as eka-radon or element 118, is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. On the periodic table of the elements, it is a p-block element and the last one of the 7th period. Ununoctium is currently...
) the isotope
281Uub was identified as decaying by emission of a 10.68 MeV alpha particle with half-life 0.90 ms. The claim was retracted in 2001 and hence this ununbium isotope is currently unknown or unconfirmed.
Chronology of isotope discovery
| Isotope | Year discovered | discovery reaction |
|---|
| 277Uub |
1996 |
208Pb(70Zn,n) |
| 278Uub |
unknown |
|
| 279Uub |
unknown |
|
| 280Uub |
unknown |
|
| 281Uub |
unknown |
|
| 282Uub |
2004 |
238U(48Ca,4n) |
| 283Uub |
2002 |
244Pu(48Ca,5n) |
| 283bUub ?? |
1998 |
238U(48Ca,3n) |
| 284Uub |
2002 |
244Pu(48Ca,4n) |
| 285Uub |
1999 |
244Pu(48Ca,3n) |
| 285bUub ? |
1999 |
244Pu(48Ca,3n) |
-
Nuclear isomerism
285a,bUub
In the synthesis of
289Uuq and
293Uuh, a 8.63 MeV alpha-decaying activity has been detected with a half-life of 8.9 minutes. Although unconfirmed in recent experiments, it is highly possible that this is associated with an isomer, namely
285bUub.
283a,bUub
First experiments on the synthesis of
283Uub produced a SF activity with half-life ~5 min. This activity was also observed from the alpha decay of
287Uuq. The decay mode and half-life were also confirmed in a repeat of the first experiment. However, more recently,
283Uub has been observed to undergo 9.52 MeV alpha decay and SF with a half-life of 3.9 s. These results suggest the assignment of the two activities to two different isomeric levels in
283Uub, creating
283aUub and
283bUub. Further research is required to address these discrepancies.
Cold fusion
The table below provides cross-sections and excitation energies for
cold fusionCold fusion refers to a proposed nuclear fusion process of unknown mechanism offered to explain a group of disputed experimental results first reported by electrochemists Martin Fleischmann and Stanley Pons...
reactions producing ununbium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.
| Projectile | Target | CN | 1n | 2n | 3n |
|---|
| 70Zn |
208Pb}>278Uub |
0.5 pb, 10.0, 12.0 MeV |
|
|
| 68Zn |
208Pb |
276Uub |
<1.2 pb, 11.3, 12.8 MeV |
|
|
Hot fusion
The table below provides cross-sections and excitation energies for hot fusion reactions producing ununbium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.
| Projectile | Target | CN | 3n | 4n | 5n |
|---|
| 48Ca |
238U |
286Uub |
2.5 pb, 35.0 MeV |
0.6 pb |
|
| 48Ca |
233U |
281Uub |
<0.6 pb, 34.9 MeV |
|
|
Fission of compound nuclei with Z=112
Several experiments have been performed between 2001-2004 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus
286Uub. The nuclear reaction used is
238U+
48Ca. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as
132Sn (Z=50, N=82). It was also found that the yield for the fusion-fission pathway was similar between
48Ca and
58Fe projectiles, indicating a possible future use of
58Fe projectiles in superheavy element formation.
Evaporation residue cross sections
The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.
DNS = Di-nuclear system; σ = cross section
| Target | Projectile | CN | Channel (product) | σmax | Model | Ref |
|---|
| 208Pb |
70Zn |
278Uub |
1n (277Uub) |
1.5 pb |
DNS |
|
| 208Pb |
67Zn |
275Uub |
1n (274Uub) |
2 pb |
DNS |
|
| 238U |
48Ca |
286Uub |
4n (282Uub) |
0.2 pb |
DNS |
|
| 244Pu |
40Ar |
284Uub |
4n (280Uub) |
0.1 pb |
DNS |
|
| 250Cm |
36S |
286Uub |
4n (282Uub) |
5 pb |
DNS |
|
| 252Cf |
30Si |
282Uub |
3n (279Uub) |
10 pb |
DNS |
|
Oxidation states
Element 112 is projected to be the last member of the 6d series of transition metals and the heaviest member of group 12 (IIB) in the Periodic Table, below
zincZinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
,
cadmiumCadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
and
mercuryMercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80...
. Each of the members of this group show a stable +2 oxidation state. In addition, mercury(I), , is also well known. Element 112 is therefore expected to form a stable +2 state.
Chemistry
The known members of group 12 all react with
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
and
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
directly to form the
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
s and
sulfideA sulfide is a chemical compound containing sulfur in its lowest oxidation number of −2.- Properties :...
s, MO and MS, respectively. Mercury(II) oxide, HgO, can be decomposed by heat to the liquid metal. Mercury also has a well known affinity for sulfur. Therefore, element 112 should form an analogous oxide UubO and sulfide UubS.
In their
halogenThe halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine, ; chlorine, ; bromine, ; iodine, ; and astatine,...
chemistry, all the metals form the ionic difluoride MF
2 upon reaction with
fluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F
2 molecule. F
2 is a supremely reactive, poisonous, pale, yellowish brown gas. Elemental fluorine is the...
. The other halides are known but for mercury, the soft nature of the Hg(II) ion leads to a high degree of covalency and HgCl
2, HgBr
2 and HgI
2 are low-melting, volatile solids. Therefore, element 112 is expected to form an ionic fluoride, UubF
2, but volatile halides, UubCl
2, UubBr
2 and UubI
2.
In addition, mercury is well known for its
alloyAn alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history...
ing properties, with the concomitant formation of
amalgamsAn amalgam is a substance formed by the reaction of some other substance with mercury. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum...
, especially with
goldGold is a chemical element with the symbol Au and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is...
and
silverSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
. It is also a volatile metal and is
monatomicIn physics and chemistry, monatomic is a combination of the words "mono" and "atomic," and means "single atom." It is usually applied to gases: a monatomic gas is one in which atoms are not bound to each other....
in the vapour
phaseIn the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...
. Element 112 is therefore also predicted to be a volatile metal which readily combines with gold to form a Au-Uub metal-metal bond.
Atomic gas phase
Ununbium is expected to have the ground state electron configuration [Rn]5f
14 6d
10 7s
2 and thus belong to group 12 of the Periodic Table. As such, it should behave as the heavier homologue of mercury (Hg) and form strong binary compounds with noble metals like gold. Experiments probing the reactivity of ununbium have focused on the adsorption of atoms of element 112 onto a gold surface held at varying temperatures, in order to calculate an adsorption enthalpy. Due to possible relativistic stabilisation of the 7s electrons, leading to radon-like properties, experiments were performed with the simultaneous formation of mercury and radon radioisotopes, allowing a comparison of adsorption characteristics.
The first experiments were conducted using the
238U(
48Ca,3n)
283Uub reaction. Detection was by spontaneous fission of the claimed 5 min parent isotope. Analysis of the data indicated that ununbium was more volatile than mercury and had noble-gas properties. However, the confusion regarding the synthesis of
283Uub has cast some doubt on these experimental results.
Given this uncertainty, between April-May 2006 at the JINR, a FLNR-PSI team conducted experiments probing the synthesis of this isotope as a daughter in the nuclear reaction
242Pu(
48Ca,3n)
287Uuq. In this experiment, two atoms of
283Uub were unambiguously identified and the adsorption properties indicated that ununbium is a more volatile homologue of mercury, due to formation of a weak metal-metal bond with gold, placing it firmly in group 12.
In April 2007 this experiment was repeated and a further 3 atoms of
283112 were positively identified. The adsorption property was confirmed and indicated that element 112 has adsorption properties completely in agreement with being the heaviest member of group 12.
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