Ununquadium
Encyclopedia
Ununquadium is the temporary name of a radioactive chemical element
with the temporary symbol Uuq and atomic number
114. There is no proposed name yet, although flerovium (after Soviet physicist Georgy Flyorov
, the founder of the Joint Institute for Nuclear Research
in Dubna
, Russia
, where the element was discovered) has been discussed in the media.
About 80 decay
s of atoms of ununquadium have been observed to date, 50 directly and 30 from the decay of the heavier elements ununhexium
and ununoctium
. All decays have been assigned to the five neighbouring isotope
s with mass numbers 285–289. The longest-lived isotope currently known is 289Uuq with a half-life of ~2.6 s, although there is evidence for a nuclear isomer
, 289bUuq, with a half-life of ~66 s, that would be one of the longest-lived nuclei in the superheavy element region.
Chemical studies performed in 2007 strongly indicate that ununquadium possesses non-eka-lead
properties and appears to behave as the first superheavy element that portrays noble-gas
-like properties due to relativistic effects
.
) in Russia bombarded a 244Pu target with 48Ca ions. A single atom of ununquadium, decaying by 9.67 MeV alpha-emission with a half-life of 30 s, was produced and assigned to 289114. This observation was subsequently published in January 1999. However, the decay chain observed has not been repeated and the exact identity of this activity is unknown, although it is possible that it is due to a meta-stable isomer, namely 289mUuq.
In March 1999, the same team replaced the 244Pu target with a 242Pu one in order to produce other isotopes. This time two atoms of ununquadium were produced, decaying by 10.29 MeV alpha-emission with a half-life of 5.5 s. They were assigned as 287Uuq. Once again, this activity has not been seen again and it is unclear what nucleus was produced. It is possible that it was a meta-stable isomer, namely 287mUuq.
The now-confirmed discovery of ununquadium was made in June 1999 when the Dubna team repeated the 244Pu reaction. This time, two atoms of element 114 were produced decaying by emission of 9.82 MeV alpha particles with a half-life of 2.6 s.
This activity was initially assigned to 288Uuq in error, due to the confusion regarding the above observations. Further work in Dec 2002 has allowed a positive reassignment to 289114.
In May 2009, the Joint Working Party (JWP) of IUPAC published a report on the discovery of copernicium in which they acknowledged the discovery of the isotope 283Cn. This therefore implies the de facto discovery of ununquadium, from the acknowledgment of the data for the synthesis of 287Uuq and 291Uuh
(see below), relating to 283Cn. In 2011, IUPAC evaluated the Dubna team experiments of 1999–2007. Whereas they found the early data inconclusive, the results of 2004–2007 were accepted as identification of element 114.
The discovery of ununquadium, as 287Uuq and 286Uuq, was confirmed in January 2009 at Berkeley. This was followed by confirmation of 288Uuq and 289Uuq in July 2009 at the GSI (see section 2.1.3).
. The element is often referred to as element 114, for its atomic number.
According to IUPAC recommendations, the discoverer(s) of a new element has the right to suggest a name.
The discovery of ununquadium was recognized by JWG of IUPAC on 1 June 2011, along with that of ununhexium
. According to the vice-director of JINR, the Dubna team would like to name element 114 flerovium, after Soviet physicist Georgy Flyorov
(also spelled Flerov).
have indicated plans to study the cold fusion reaction:
The FLNR have future plans to study light isotopes of ununquadium, formed in the reaction between 239Pu and 48Ca.
of 114.
The first attempt to synthesise ununquadium in cold fusion reactions was performed at Grand accélérateur national d'ions lourds (GANIL), France in 2003. No atoms were detected providing a yield limit of 1.2 pb.
The first experiments on the synthesis of ununquadium were performed by the team in Dubna in November 1998. They were able to detect a single, long decay chain, assigned to . The reaction was repeated in 1999 and a further two atoms of ununquadium were detected. The products were assigned to . The team further studied the reaction in 2002. During the measurement of the 3n, 4n, and 5n neutron evaporation excitation functions they were able to detect three atoms of , twelve atoms of the new isotope , and one atom of the new isotope 287Uuq. Based on these results, the first atom to be detected was tentatively reassigned to or 289mUuq, whilst the two subsequent atoms were reassigned to and therefore belong to the unofficial discovery experiment. In an attempt to study the chemistry of copernicium as the isotope , this reaction was repeated in April 2007. Surprisingly, a PSI-FLNR directly detected two atoms of forming the basis for the first chemical studies of ununquadium.
In June 2008, the experiment was repeated in order to further assess the chemistry of the element using the isotope. A single atom was detected seeming to confirm the noble-gas-like properties of the element.
During May–July 2009, the team at GSI studied this reaction for the first time, as a first step towards the synthesis of ununseptium
. The team were able to confirm the synthesis and decay data for and , producing nine atoms of the former isotope and four atoms of the latter.
The team at Dubna first studied this reaction in March–April 1999 and detected two atoms of ununquadium, assigned to 287Uuq. The reaction was repeated in September 2003 in order to attempt to confirm the decay data for 287Uuq and 283Cn since conflicting data for 283Cn had been collected (see copernicium). The Russian scientists were able to measure decay data for 288Uuq, 287Uuq and the new isotope 286Uuq from the measurement of the 2n, 3n, and 4n excitation functions.
In April 2006, a PSI-FLNR collaboration used the reaction to determine the first chemical properties of copernicium by producing 283Cn as an overshoot product. In a confirmatory experiment in April 2007, the team were able to detect 287Uuq directly and therefore measure some initial data on the atomic chemical properties of ununquadium.
The team at Berkeley, using the Berkeley gas-filled separator (BGS), continued their studies using newly acquired targets by attempting the synthesis of ununquadium in January 2009 using the above reaction. In September 2009, they reported that they had succeeded in detecting two atoms of ununquadium, as and , confirming the decay properties reported at the FLNR, although the measured cross sections were slightly lower; however the statistics were of lower quality.
In April 2009, the collaboration of Paul Scherrer Institute
(PSI) and Flerov Laboratory of Nuclear Reactions (FLNR) of JINR carried out another study of the chemistry of ununquadium using this reaction. A single atom of 283Cn was detected.
In December 2010, the team at the LBNL announced the synthesis of a single atom of the new isotope 285Uuq with the consequent observation of 5 new isotopes of daughter elements.
s of ununhexium
and ununoctium
.
In the claimed synthesis of 293Uuo in 1999, the isotope 285Uuq was identified as decaying by 11.35 MeV alpha emission with a half-life
of 0.58 ms. The claim was retracted in 2001. This isotope was finally created in 2010 and its decay properties supported the fabrication of the previously published decay data.
MD = multi-dimensional; DNS = Dinuclear system; σ = cross section
The fission-survived isotope 298Uuq is predicted to have alpha decay half-life around 17 days.
In the region of Z=114, MM theory indicates that N=184 is the next spherical neutron magic number and puts forward the nucleus 298Uuq as a strong candidate for the next spherical doubly magic nucleus, after 208Pb (Z=82, N=126). 298Uuq is taken to be at the centre of a hypothetical "island of stability
". However, other calculations using relativistic mean field (RMF) theory propose Z=120, 122, and 126 as alternative proton magic numbers depending upon the chosen set of parameters. It is possible that rather than a peak at a specific proton shell, there exists a plateau of proton shell effects from Z=114–126.
It should be noted that calculations suggest that the minimum of the shell-correction energy and hence the highest fission barrier exists for 297Uup
, caused by pairing effects. Due to the expected high fission barriers, any nucleus within this island of stability will exclusively decay by alpha-particle emission and as such the nucleus with the longest half-life
is predicted to be 298Uuq. The expected half-life
is unlikely to reach values higher than about 10 minutes, unless the N=184 neutron shell proves to be more stabilising than predicted, for which there exists some evidence. In addition, 297Uuq may have an even-longer half-life
due to the effect of the odd neutron, creating transitions between similar Nilsson levels with lower Qalpha values.
In either case, an island of stability does not represent nuclei with the longest half-lives but those which are significantly stabilized against fission by closed-shell effects.
and 292Uuo
(both N=174 isotones). The extraction of Z=114 effects is complicated by the presence of a dominating N=184 effect in this region.
It has been suggested that such a neutron-rich isotope can be formed by the quasifission (partial fusion followed by fission) of a massive nucleus. Such nuclei tend to fission with the formation of isotopes close to the closed shells Z=20/N=20 (40Ca), Z=50/N=82 (132Sn) or Z=82/N=126 (208Pb/209Bi). If Z=114 does represent a closed shell, then the hypothetical reaction below may represent a method of synthesis:
Recently it has been shown that the multi-nucleon transfer reactions in collisions of actinide nuclei (such as uranium
and curium
) might be used to synthesize the neutron rich superheavy nuclei located at the island of stability
.
It is also possible that 298Uuq can be synthesized by the alpha decay of a massive nucleus. Such a method would depend highly on the SF stability of such nuclei, since the alpha half-lives are expected to be very short. The yields for such reactions will also most likely be extremely small. One such reaction is:
s and the heaviest member of group 14 (IVA) in the Periodic Table, below lead
. Each of the members of this group show the group oxidation state of +IV and the latter members have an increasing +II chemistry due to the onset of the inert pair effect
. Tin
represents the point at which the stability of the +II and +IV states are similar. Lead
, the heaviest member, portrays a switch from the +IV state to the +II state. Ununquadium should therefore follow this trend and a possess an oxidising +IV state and a stable +II state.
Some studies also suggest that the chemical behaviour of ununquadium might in fact be closer to that of the noble gas radon
, than to that of lead.
via comparison with published decay data. Further experiments were performed in 2008 to confirm this important result and a single atom of 289Uuq was detected which gave data in agreement with previous data in support of ununquadium having a noble-gas-like interaction with gold.
In April 2009, the FLNR-PSI collaboration synthesized a further atom of element 114.
Chemical element
A 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. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the temporary symbol Uuq and atomic number
Atomic number
In 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...
114. There is no proposed name yet, although flerovium (after Soviet physicist Georgy Flyorov
Georgy Flyorov
Georgy Nikolayevich Flyorov was a prominent Soviet nuclear physicist.-Biography:Flyorov was born in Rostov-on-Don and attended the Leningrad Polytechnic Institute Georgy Nikolayevich Flyorov (March 2, 1913 – November 19, 1990) was a prominent Soviet nuclear physicist.-Biography:Flyorov was born...
, the founder of the Joint Institute for Nuclear Research
Joint Institute for Nuclear Research
The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow Oblast , Russia, is an international research centre for nuclear sciences, with 5500 staff members, 1200 researchers including 1000 Ph.D.s from eighteen member states The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow...
in Dubna
Dubna
Dubna is a town in Moscow Oblast, Russia. It has a status of naukograd , being home to the Joint Institute for Nuclear Research, an international nuclear physics research centre and one of the largest scientific foundations in the country. It is also home to MKB Raduga, a defence aerospace company...
, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, where the element was discovered) has been discussed in the media.
About 80 decay
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
s of atoms of ununquadium have been observed to date, 50 directly and 30 from the decay of the heavier elements ununhexium
Ununhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
and ununoctium
Ununoctium
Ununoctium is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. It is also known as eka-radon or element 118, and on the periodic table of the elements it is a p-block element and the last one of the 7th period. Ununoctium is...
. All decays have been assigned to the five neighbouring isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s with mass numbers 285–289. The longest-lived isotope currently known is 289Uuq with a half-life of ~2.6 s, although there is evidence for a nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
, 289bUuq, with a half-life of ~66 s, that would be one of the longest-lived nuclei in the superheavy element region.
Chemical studies performed in 2007 strongly indicate that ununquadium possesses non-eka-lead
Mendeleev's predicted elements
Professor Dmitri Mendeleev published the first Periodic Table of the Atomic Elements in 1869 based on properties which appeared with some regularity as he laid out the elements from lightest to heaviest....
properties and appears to behave as the first superheavy element that portrays noble-gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
-like properties due to relativistic effects
Relativistic quantum chemistry
Relativistic quantum chemistry invokes quantum chemical and relativistic mechanical arguments to explain elemental properties and structure, especially for heavy elements of the periodic table....
.
Discovery
In December 1998, scientists at Dubna (Joint Institute for Nuclear ResearchJoint Institute for Nuclear Research
The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow Oblast , Russia, is an international research centre for nuclear sciences, with 5500 staff members, 1200 researchers including 1000 Ph.D.s from eighteen member states The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow...
) in Russia bombarded a 244Pu target with 48Ca ions. A single atom of ununquadium, decaying by 9.67 MeV alpha-emission with a half-life of 30 s, was produced and assigned to 289114. This observation was subsequently published in January 1999. However, the decay chain observed has not been repeated and the exact identity of this activity is unknown, although it is possible that it is due to a meta-stable isomer, namely 289mUuq.
In March 1999, the same team replaced the 244Pu target with a 242Pu one in order to produce other isotopes. This time two atoms of ununquadium were produced, decaying by 10.29 MeV alpha-emission with a half-life of 5.5 s. They were assigned as 287Uuq. Once again, this activity has not been seen again and it is unclear what nucleus was produced. It is possible that it was a meta-stable isomer, namely 287mUuq.
The now-confirmed discovery of ununquadium was made in June 1999 when the Dubna team repeated the 244Pu reaction. This time, two atoms of element 114 were produced decaying by emission of 9.82 MeV alpha particles with a half-life of 2.6 s.
This activity was initially assigned to 288Uuq in error, due to the confusion regarding the above observations. Further work in Dec 2002 has allowed a positive reassignment to 289114.
- + → → + 3
In May 2009, the Joint Working Party (JWP) of IUPAC published a report on the discovery of copernicium in which they acknowledged the discovery of the isotope 283Cn. This therefore implies the de facto discovery of ununquadium, from the acknowledgment of the data for the synthesis of 287Uuq and 291Uuh
Ununhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
(see below), relating to 283Cn. In 2011, IUPAC evaluated the Dubna team experiments of 1999–2007. Whereas they found the early data inconclusive, the results of 2004–2007 were accepted as identification of element 114.
The discovery of ununquadium, as 287Uuq and 286Uuq, was confirmed in January 2009 at Berkeley. This was followed by confirmation of 288Uuq and 289Uuq in July 2009 at the GSI (see section 2.1.3).
Naming
Ununquadium (Uuq) is a temporary IUPAC systematic element nameSystematic element name
A 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 name and symbol only after its synthesis has been confirmed. In some cases, this has been a protracted and...
. The element is often referred to as element 114, for its atomic number.
According to IUPAC recommendations, the discoverer(s) of a new element has the right to suggest a name.
The discovery of ununquadium was recognized by JWG of IUPAC on 1 June 2011, along with that of ununhexium
Ununhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
. According to the vice-director of JINR, the Dubna team would like to name element 114 flerovium, after Soviet physicist Georgy Flyorov
Georgy Flyorov
Georgy Nikolayevich Flyorov was a prominent Soviet nuclear physicist.-Biography:Flyorov was born in Rostov-on-Don and attended the Leningrad Polytechnic Institute Georgy Nikolayevich Flyorov (March 2, 1913 – November 19, 1990) was a prominent Soviet nuclear physicist.-Biography:Flyorov was born...
(also spelled Flerov).
Future experiments
The team at RIKENRIKEN
is 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...
have indicated plans to study the cold fusion reaction:
- + → * → ?
The FLNR have future plans to study light isotopes of ununquadium, formed in the reaction between 239Pu and 48Ca.
Target-Projectile combinations leading to Z=114 compound nuclei
The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with an atomic numberAtomic number
In 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...
of 114.
| Target | Projectile | CN | Attempt result |
|---|---|---|---|
| 208Pb | 76Ge | 284Uuq | |
| 232Th | 54Cr | 286Uuq | |
| 238U | 50Ti | 288Uuq | |
| 244Pu | 48Ca | 292Uuq | |
| 242Pu | 48Ca | 290Uuq | |
| 239Pu | 48Ca | 287Uuq | |
| 248Cm | 40Ar | 288Uuq | |
| 249Cf | 36S | 285Uuq |
Cold fusion
This section deals with the synthesis of nuclei of ununquadium 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(76Ge,xn)284−xUuq
The first attempt to synthesise ununquadium in cold fusion reactions was performed at Grand accélérateur national d'ions lourds (GANIL), France in 2003. No atoms were detected providing a yield limit of 1.2 pb.
Hot fusion
This section deals with the synthesis of nuclei of ununquadium 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. 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.244Pu(48Ca,xn)292−xUuq (x=3,4,5)
The first experiments on the synthesis of ununquadium were performed by the team in Dubna in November 1998. They were able to detect a single, long decay chain, assigned to . The reaction was repeated in 1999 and a further two atoms of ununquadium were detected. The products were assigned to . The team further studied the reaction in 2002. During the measurement of the 3n, 4n, and 5n neutron evaporation excitation functions they were able to detect three atoms of , twelve atoms of the new isotope , and one atom of the new isotope 287Uuq. Based on these results, the first atom to be detected was tentatively reassigned to or 289mUuq, whilst the two subsequent atoms were reassigned to and therefore belong to the unofficial discovery experiment. In an attempt to study the chemistry of copernicium as the isotope , this reaction was repeated in April 2007. Surprisingly, a PSI-FLNR directly detected two atoms of forming the basis for the first chemical studies of ununquadium.
In June 2008, the experiment was repeated in order to further assess the chemistry of the element using the isotope. A single atom was detected seeming to confirm the noble-gas-like properties of the element.
During May–July 2009, the team at GSI studied this reaction for the first time, as a first step towards the synthesis of ununseptium
Ununseptium
Ununseptium is the temporary name of a superheavy artificial chemical element with temporary symbol Uus and atomic number 117. Six atoms were detected by a joint Russia–US collaboration at Dubna, Moscow Oblast, Russia, in 2009–10...
. The team were able to confirm the synthesis and decay data for and , producing nine atoms of the former isotope and four atoms of the latter.
242Pu(48Ca,xn)290−x114 (x=2,3,4,5)
The team at Dubna first studied this reaction in March–April 1999 and detected two atoms of ununquadium, assigned to 287Uuq. The reaction was repeated in September 2003 in order to attempt to confirm the decay data for 287Uuq and 283Cn since conflicting data for 283Cn had been collected (see copernicium). The Russian scientists were able to measure decay data for 288Uuq, 287Uuq and the new isotope 286Uuq from the measurement of the 2n, 3n, and 4n excitation functions.
In April 2006, a PSI-FLNR collaboration used the reaction to determine the first chemical properties of copernicium by producing 283Cn as an overshoot product. In a confirmatory experiment in April 2007, the team were able to detect 287Uuq directly and therefore measure some initial data on the atomic chemical properties of ununquadium.
The team at Berkeley, using the Berkeley gas-filled separator (BGS), continued their studies using newly acquired targets by attempting the synthesis of ununquadium in January 2009 using the above reaction. In September 2009, they reported that they had succeeded in detecting two atoms of ununquadium, as and , confirming the decay properties reported at the FLNR, although the measured cross sections were slightly lower; however the statistics were of lower quality.
In April 2009, the collaboration of Paul Scherrer Institute
Paul Scherrer Institute
The Paul Scherrer Institute is a multi-disciplinary research institute which belongs to the Swiss ETH-Komplex covering also the ETH Zurich and EPFL...
(PSI) and Flerov Laboratory of Nuclear Reactions (FLNR) of JINR carried out another study of the chemistry of ununquadium using this reaction. A single atom of 283Cn was detected.
In December 2010, the team at the LBNL announced the synthesis of a single atom of the new isotope 285Uuq with the consequent observation of 5 new isotopes of daughter elements.
As a decay product
The isotopes of ununquadium have also been observed in the decay chainDecay chain
In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
s of ununhexium
Ununhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
and ununoctium
Ununoctium
Ununoctium is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. It is also known as eka-radon or element 118, and on the periodic table of the elements it is a p-block element and the last one of the 7th period. Ununoctium is...
.
| Evaporation residue | Observed Uuq isotope |
|---|---|
| 293Uuh | 289Uuq |
| 292Uuh | 288Uuq |
| 291Uuh | 287Uuq |
| 294Uuo, 290Uuh | 286Uuq |
285Uuq
In the claimed synthesis of 293Uuo in 1999, the isotope 285Uuq was identified as decaying by 11.35 MeV alpha emission with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 0.58 ms. The claim was retracted in 2001. This isotope was finally created in 2010 and its decay properties supported the fabrication of the previously published decay data.
Chronology of isotope discovery
| Isotope | Year discovered | Discovery reaction |
|---|---|---|
| 285Uuq | 2010 | 242Pu(48Ca,5n) |
| 286Uuq | 2002 | 249Cf(48Ca,3n) |
| 287aUuq | 2002 | 244Pu(48Ca,5n) |
| 287bUuq ?? | 1999 | 242Pu(48Ca,3n) |
| 288Uuq | 2002 | 244Pu(48Ca,4n) |
| 289aUuq | 1999 | 244Pu(48Ca,3n) |
| 289bUuq ? | 1998 | 244Pu(48Ca,3n) |
Fission of compound nuclei with an atomic number of 114
Several experiments have been performed between 2000–2004 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus 292Uuq. The nuclear reaction used is 244Pu+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.289Uuq
In the first claimed synthesis of ununquadium, an isotope assigned as 289Uuq decayed by emitting a 9.71 MeV alpha particle with a lifetime of 30 seconds. This activity was not observed in repetitions of the direct synthesis of this isotope. However, in a single case from the synthesis of 293Uuh, a decay chain was measured starting with the emission of a 9.63 MeV alpha particle with a lifetime of 2.7 minutes. All subsequent decays were very similar to that observed from 289Uuq, presuming that the parent decay was missed. This strongly suggests that the activity should be assigned to an isomeric level. The absence of the activity in recent experiments indicates that the yield of the isomer is ~20% compared to the supposed ground state and that the observation in the first experiment was a fortunate (or not as the case history indicates). Further research is required to resolve these issues.287Uuq
In a manner similar to those for 289Uuq, first experiments with a 242Pu target identified an isotope 287Uuq decaying by emission of a 10.29 MeV alpha particle with a lifetime of 5.5 seconds. The daughter spontaneously fissioned with a lifetime in accord with the previous synthesis of 283Cn. Both these activities have not been observed since (see copernicium). However, the correlation suggests that the results are not random and are possible due to the formation of isomers whose yield is obviously dependent on production methods. Further research is required to unravel these discrepancies.Yields of isotopes
The tables below provide cross-sections and excitation energies for fusion reactions producing ununquadium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.Cold fusion
| Projectile | Target | CN | 1n | 2n | 3n |
|---|---|---|---|---|---|
| 76Ge | 208Pb | 284Uuq | <1.2 pb |
Hot fusion
| Projectile | Target | CN | 2n | 3n | 4n | 5n |
|---|---|---|---|---|---|---|
| 48Ca | 242Pu | 290Uuq | 0.5 pb, 32.5 MeV | 3.6 pb, 40.0 MeV | 4.5 pb, 40.0 MeV | <1.4 pb, 45.0 MeV |
| 48Ca | 244Pu | 292Uuq | 1.7 pb, 40.0 MeV | 5.3 pb, 40.0 MeV | 1.1 pb, 52.0 MeV |
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.MD = multi-dimensional; DNS = Dinuclear system; σ = cross section
| Target | Projectile | CN | Channel (product) | σmax | Model | Ref |
|---|---|---|---|---|---|---|
| 208Pb | 76Ge | 284Uuq | 1n (283Uuq) | 60 fb | DNS | |
| 208Pb | 73Ge | 281Uuq | 1n (280Uuq) | 0.2 pb | DNS | |
| 238U | 50Ti | 288Uuq | 2n (286Uuq) | 60 fb | DNS | |
| 244Pu | 48Ca | 292Uuq | 4n (288Uuq) | 4 pb | MD | |
| 242Pu | 48Ca | 290Uuq | 3n (287Uuq) | 3 pb | MD |
Decay characteristics
Theoretical estimation of the alpha decay half-lives of the isotopes of the ununquadium supports the experimental data.The fission-survived isotope 298Uuq is predicted to have alpha decay half-life around 17 days.
In search for the island of stability: 298Uuq
According to macroscopic-microscopic (MM) theory, Z=114 is the next spherical magic number. This means that such nuclei are spherical in their ground state and should have high, wide fission barriers to deformation and hence long SF partial half-lives.In the region of Z=114, MM theory indicates that N=184 is the next spherical neutron magic number and puts forward the nucleus 298Uuq as a strong candidate for the next spherical doubly magic nucleus, after 208Pb (Z=82, N=126). 298Uuq is taken to be at the centre of a hypothetical "island of stability
Island of stability
The island of stability in nuclear physics describes a set of as-yet undiscovered isotopes of transuranium elements which are theorized to be much more stable than others...
". However, other calculations using relativistic mean field (RMF) theory propose Z=120, 122, and 126 as alternative proton magic numbers depending upon the chosen set of parameters. It is possible that rather than a peak at a specific proton shell, there exists a plateau of proton shell effects from Z=114–126.
It should be noted that calculations suggest that the minimum of the shell-correction energy and hence the highest fission barrier exists for 297Uup
Ununpentium
Ununpentium is the temporary name of a synthetic superheavy element in the periodic table that has the temporary symbol Uup and has the atomic number 115....
, caused by pairing effects. Due to the expected high fission barriers, any nucleus within this island of stability will exclusively decay by alpha-particle emission and as such the nucleus with the longest half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
is predicted to be 298Uuq. The expected half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
is unlikely to reach values higher than about 10 minutes, unless the N=184 neutron shell proves to be more stabilising than predicted, for which there exists some evidence. In addition, 297Uuq may have an even-longer half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
due to the effect of the odd neutron, creating transitions between similar Nilsson levels with lower Qalpha values.
In either case, an island of stability does not represent nuclei with the longest half-lives but those which are significantly stabilized against fission by closed-shell effects.
Evidence for Z=114 closed proton shell
While evidence for closed neutron shells can be deemed directly from the systematic variation of Qalpha values for ground-state to ground-state transitions, evidence for closed proton shells comes from (partial) spontaneous fission half-lives. Such data can sometimes be difficult to extract due to low production rates and weak SF branching. In the case of Z=114, evidence for the effect of this proposed closed shell comes from the comparison between the nuclei pairings 282Cn (TSF1/2 = 0.8 ms) and 286Uuq (TSF1/2 = 130 ms), and 284Cn (TSF = 97 ms) and 288Uuq (TSF >800 ms). Further evidence would come from the measurement of partial SF half-lives of nuclei with Z>114, such as 290UuhUnunhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
and 292Uuo
Ununoctium
Ununoctium is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. It is also known as eka-radon or element 118, and on the periodic table of the elements it is a p-block element and the last one of the 7th period. Ununoctium is...
(both N=174 isotones). The extraction of Z=114 effects is complicated by the presence of a dominating N=184 effect in this region.
Difficulty of synthesis of 298Uuq
The direct synthesis of the nucleus 298Uuq by a fusion-evaporation pathway is impossible since no known combination of target and projectile can provide 184 neutrons in the compound nucleus.It has been suggested that such a neutron-rich isotope can be formed by the quasifission (partial fusion followed by fission) of a massive nucleus. Such nuclei tend to fission with the formation of isotopes close to the closed shells Z=20/N=20 (40Ca), Z=50/N=82 (132Sn) or Z=82/N=126 (208Pb/209Bi). If Z=114 does represent a closed shell, then the hypothetical reaction below may represent a method of synthesis:
- + → + + 2
Recently it has been shown that the multi-nucleon transfer reactions in collisions of actinide nuclei (such as uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and curium
Curium
Curium is a synthetic chemical element with the symbol Cm and atomic number 96. This radioactive transuranic element of the actinide series was named after Marie Skłodowska-Curie and her husband Pierre Curie. Curium was first intentionally produced and identified in summer 1944 by the group of...
) might be used to synthesize the neutron rich superheavy nuclei located at the island of stability
Island of stability
The island of stability in nuclear physics describes a set of as-yet undiscovered isotopes of transuranium elements which are theorized to be much more stable than others...
.
It is also possible that 298Uuq can be synthesized by the alpha decay of a massive nucleus. Such a method would depend highly on the SF stability of such nuclei, since the alpha half-lives are expected to be very short. The yields for such reactions will also most likely be extremely small. One such reaction is:
- → → → + 10
Oxidation states
Ununquadium is projected to be the second member of the 7p series of chemical elementChemical element
A 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. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
s and the heaviest member of group 14 (IVA) in the Periodic Table, below lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
. Each of the members of this group show the group oxidation state of +IV and the latter members have an increasing +II chemistry due to the onset of the inert pair effect
Inert pair effect
The inert pair effect is the tendency of the outermost s electrons to remain nonionized or unshared in compounds of post-transition metals. The term inert pair effect is often used in relation to the increasing stability of oxidation states that are 2 less than the group valency for the heavier...
. Tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
represents the point at which the stability of the +II and +IV states are similar. Lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, the heaviest member, portrays a switch from the +IV state to the +II state. Ununquadium should therefore follow this trend and a possess an oxidising +IV state and a stable +II state.
Chemistry
Ununquadium should portray eka-lead chemical properties and should therefore form a monoxide, UuqO, and dihalides, UuqF2, UuqCl2, UuqBr2, and UuqI2. If the +IV state is accessible, it is likely that it is only possible in the oxide, UuqO2, and fluoride, UuqF4. It may also show a mixed oxide, Uuq3O4, analogous to Pb3O4.Some studies also suggest that the chemical behaviour of ununquadium might in fact be closer to that of the noble gas radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...
, than to that of lead.
Atomic gas phase
Two experiments were performed in April–May 2007 in a joint FLNR-PSI collaboration aiming to study the chemistry of copernicium. The first experiment involved the reaction 242Pu(48Ca,3n)287Uuq and the second the reaction 244Pu(48Ca,4n)288Uuq. The adsorption properties of the resultant atoms on a gold surface were compared with those of radon. The first experiment allowed detection of 3 atoms of 283Cn but also seemingly detected 1 atom of 287Uuq. This result was a surprise given the transport time of the product atoms is ~2 s, so ununquadium atoms should decay before adsorption. In the second reaction, 2 atoms of 288Uuq and possibly 1 atom of 289Uuq were detected. Two of the three atoms portrayed adsorption characteristics associated with a volatile, noble-gas-like element, which has been suggested but is not predicted by more recent calculations. These experiments did however provide independent confirmation for the discovery of copernicium, ununquadium, and ununhexiumUnunhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...
via comparison with published decay data. Further experiments were performed in 2008 to confirm this important result and a single atom of 289Uuq was detected which gave data in agreement with previous data in support of ununquadium having a noble-gas-like interaction with gold.
In April 2009, the FLNR-PSI collaboration synthesized a further atom of element 114.
See also
- Island of stabilityIsland of stabilityThe island of stability in nuclear physics describes a set of as-yet undiscovered isotopes of transuranium elements which are theorized to be much more stable than others...
: Ununquadium–UnbiniliumUnbiniliumUnbinilium , also called eka-radium or element 120, is the temporary, systematic element name of a hypothetical chemical element in the periodic table that has the temporary symbol Ubn and has the atomic number 120....
–UnbihexiumUnbihexiumUnbihexium , also known as eka-plutonium or element 126, is a hypothetical chemical element with atomic number 126 and symbol Ubh. It is of interest because of its location at the peak of the hypothesized island of stability.-History:... - LeadLeadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
- Periodic table (extended)
- Isotopes of ununquadiumIsotopes of ununquadiumUnunquadium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 289Uuq in 1999 . Ununquadium has five confirmed isotopes, and possibly 2 nuclear isomers...