Ununquadium

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114 ununtrium ← ununquadium → ununpentium Pb ↑ Uuq ↓ (Uhq) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	ununquadium, Uuq, 114
Element category	Unknown, suspected to be a noble gas
Group, Period, Block	14, 7, p
Appearance	unknown
Standard atomic weight	[289] g·mol−1
Electron configuration	perhaps [Rn] 5f14 6d10 7s2 7p2 (guess based on lead)
Electrons per shell	2, 8, 18, 32, 32, 18, 4
Phase	unknown
CAS registry number	54085-16-4
Most-stable isotopes
Main article: Isotopes of ununquadium iso NA half-life DM DE (MeV) DP 289Uuq syn 2.6 s α 9.82,9.48 285Uub 288Uuq syn 0.8 s α 9.94 284Uub 287Uuq syn 0.48 s α 10.02 283Uub 286Uuq syn 0.13 s 40% α 10.19 282Uub 60% SF
References

Ununquadium (pronounced /ˌjuːnənˈkwɒdiəm/;^[1] officially, the two initial u's are to be pronounced /uː/  ( listen)^[2]) is the temporary name of a radioactive chemical element in the periodic table that has the temporary symbol Uuq and has the atomic number 114.

	Ununquadium Common English pronunciation of ununquadium
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Recent chemistry experiments have strongly indicated that element 114 possesses non eka-lead properties and appears to behave as the first superheavy element to show noble-gas-like properties due to relativistic effects.^[3]

Contents 1 De facto discovery 2 Naming 2.1 Current names 2.2 Proposed names by claimants 3 Extrapolated chemical properties of eka-lead 3.1 Oxidation states 3.2 Chemistry 4 Experimental chemistry 4.1 Atomic gas phase 5 History of synthesis of isotopes by cold fusion 5.1 208Pb(76Ge,xn)284−x114 6 History of synthesis of isotopes by hot fusion 6.1 244Pu(48Ca,xn)292−x114 (x=3,4,5) 6.2 242Pu(48Ca,xn)290−x114 (x=2,3,4) 7 Synthesis of isotopes as decay products 8 Chronology of isotope discovery 9 Yields of isotopes 9.1 Cold fusion 9.2 Hot fusion 10 Isomerism in ununquadium isotopes 10.1 289114 10.2 287114 11 Retracted isotopes 11.1 285114 12 In search for the island of stability: 298114 12.1 Evidence for Z=114 closed proton shell 12.2 Difficulty in synthesis 13 Currently running experiments 14 Future experiments 15 See also 16 References 17 External links

[edit] De facto discovery

In December 1998, scientists at Dubna (Joint Institute for Nuclear Research) in Russia bombarded a Pu-244 target with Ca-48 ions. A single atom of element 114, 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.^[4] 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 ^289m114.

In March 1999, the same team replaced the Pu-244 target with a Pu-242 one in order to produce other isotopes. This time two atoms of element 114 were produced, decaying by 10.29 MeV alpha-emission with a half-life of 5.5 s. They were assigned as ²⁸⁷114.^[5] 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 ^287m114.

The now-confirmed discovery of element 114 was made in June 1999 when the Dubna team repeated the Pu-244 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.^[6]

This activity was initially assigned to ²⁸⁸114 in error, due to the confusion regarding the above observations. Further work in Dec 2002 has allowed a positive reassignment to ²⁸⁹114.^[7]

24494Pu + 4820Ca → 292114Uuq^* → 289114Uuq + 3 10n

Theoretical estimation of the alpha decay half lives of the isotopes of the element 114 supports the experimental data.^[8][9] The fission-survived isotope ²⁹⁸114 is predicted to have alpha decay half life around 17 days.^[10][11]

In May 2009, the JWP published a report on the discovery of element 112 ununbium in which they acknowledged the discovery of the isotope ²⁸³112.^[12] This therefore implies the de facto discovery of element 114, from the acknowledgment of the data for the synthesis of ²⁸⁷114 and ²⁹¹116 (see below), relating to ²⁸³112, although this may not be determined as the first synthesis of the element. An impending report by the JWP will discuss these issues.

[edit] Naming

[edit] Current names

Ununquadium (Uuq) is a temporary IUPAC systematic element name. Research scientists usually^{[citation needed]} refer to the element simply as element 114.

[edit] Proposed names by claimants

According to IUPAC recommendations, the discoverer(s)of a new element has the right to suggest a name.^[13] No naming suggestions have yet been given by the (claimant) discoverers.

[edit] Extrapolated chemical properties of eka-lead

[edit] Oxidation states

Element 114 is projected to be the second member of the 7p series of non-metals 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. Element 114 should therefore follow this trend and a possess an oxidising +IV state and a stable +II state.

[edit] Chemistry

Element 114 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 element 114 might in fact be closer to that of the noble gas radon, than to that of lead.^[3]

[edit] Experimental chemistry

[edit] Atomic gas phase

Two experiments were performed in April-May 2007 in a joint FLNR-PSI collaboration aiming to study the chemistry of element 112. The first experiment involved the reaction ²⁴²Pu(⁴⁸Ca,3n)²⁸⁷114 and the second the reaction ²⁴⁴Pu(⁴⁸Ca,4n)²⁸⁸114. 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 ²⁸³112 (see ununbium) but also seemingly detected 1 atom of ²⁸⁷114. This result was a surprise given the transport time of the product atoms is ~2 s, so element 114 atoms should decay before adsorption. In the second reaction, 2 atoms of ²⁸⁸114 and possibly 1 atom of ²⁸⁹114 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 elements 112, 114, and 116 via comparison with published decay data. Further experiments were performed in 2008 to confirm this important result and a single atom of ²⁸⁹114 was detected which gave data in agreement with previous data in support of element 114 having a noble-gas-like interaction with gold.^[14]

[edit] History of synthesis of isotopes by cold fusion

[edit] ²⁰⁸Pb(⁷⁶Ge,xn)^284−x114

The first attempt to synthesise element 114 in cold fusion reactions was performed at GANIL, France in 2003. No atoms were detected providing a yield limit of 1.2 pb.

[edit] History of synthesis of isotopes by hot fusion

[edit] ²⁴⁴Pu(⁴⁸Ca,xn)^292−x114 (x=3,4,5)

The first experiments on the synthesis of element 114 were performed by the team in Dubna in November 1998. They were able to detect a single, long decay chain, assigned to ²⁸⁹114.^[4] The reaction was repeated in 1999 and a further 2 atoms of element 114 were detected. The products were assigned to ²⁸⁸114.^[6] 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 3 atoms of ²⁸⁹114, 12 atoms of the new isotope ²⁸⁸114, and 1 atom of the new isotope ²⁸⁷114. Based on these results, the first atom to be detected was tentatively reassigned to ²⁹⁰114 or ^289m114, whilst the two subsequent atoms were reassigned to ²⁸⁹114 and therefore belong to the unofficial discovery experiment.^[7] In an attempt to study the chemistry of element 112 as the isotope ²⁸⁵112, this reaction was repeated in April 2007. Surprisingly, a PSI-FLNR directly detected 2 atoms of ²⁸⁸114 forming the basis for the first chemical studies of element 114. In June 2008, the experiment was repeated in order to further assess the chemistry of the element using the ²⁸⁹114 isotope. A single atom was detected seeming to confirm the noble-gas-like properties of the element.

[edit] ²⁴²Pu(⁴⁸Ca,xn)^290−x114 (x=2,3,4)

The team at Dubna first studied this reaction in March-April 1999 and detected two atoms of element 114, assigned to ²⁸⁷114.^[5] The reaction was repeated in September 2003 in order to attempt to confirm the decay data for ²⁸⁷114 and ²⁸³112 since conflicting data for ²⁸³112 had been collected (see ununbium). The Russian scientists were able to measure decay data for ²⁸⁸114,²⁸⁷114 and the new isotope ²⁸⁶114 from the measurement of the 2n, 3n, and 4n excitation functions. ^{[15] [16]} In April 2006, a PSI-FLNR collaboration used the reaction to determine the first chemical properties of element 112 by producing ²⁸³112 as an overshoot product. In a confirmatory experiment in April 2007, the team were able to detect ²⁸⁷114 directly and therefore measure some initial data on the atomic chemical properties of element 114.

[edit] Synthesis of isotopes as decay products

The isotopes of ununquadium have also been observed in the decay of elements 116 and 118 (see ununoctium for decay chain).

Evaporation residue	Observed Uuq isotope
293116	289114 [17][16]
292116	288114 [16]
291116	287114 [7]
294118, 290116	286114 [18]

[edit] Chronology of isotope discovery

Isotope	Year discovered	Discovery reaction
286Uuq	2002	249Cf(48Ca,3n) [18]
287Uuq	2002	244Pu(48Ca,5n)
288Uuq	2002	244Pu(48Ca,4n)
289Uuq	1998?, 1999	244Pu(48Ca,3n)

[edit] 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.

[edit] Cold fusion

Projectile	Target	CN	1n	2n	3n
76Ge	208Pb	284Uuq	< 1.2 pb

[edit] 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

[edit] Isomerism in ununquadium isotopes

[edit] ²⁸⁹114

In the first claimed synthesis of element 114, an isotope assigned as ²⁸⁹114 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 ²⁹³116, 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 ²⁸⁹114, 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.

[edit] ²⁸⁷114

In a manner similar to those for ²⁸⁹114, first experiments with a ²⁴²Pu target identified an isotope ²⁸⁷114 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 ²⁸³112. Both these acitivities have not been observed since (see ununbium). 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.

[edit] Retracted isotopes

[edit] ²⁸⁵114

In the claimed synthesis of ²⁹³118 in 1999, the isotope ²⁸⁵114 was identified as decaying by 11.35 MeV alpha emission with a half-life of 0.58 ms. The claim was retracted in 2001 and hence this ununquadium isotope is currently unknown or unconfirmed.

[edit] In search for the island of stability: ²⁹⁸114

According to macroscopic-microscopic (MM) theory^{[citation needed]}, 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 ²⁹⁸114 as a strong candidate for the next spherical doubly magic nucleus, after ²⁰⁸Pb (Z=82, N=126). ²⁹⁸114 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 ²⁹⁷115, 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 ²⁹⁸114. 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.^{[citation needed]} In addition, ²⁹⁷114 may have an even-longer half-life due to the effect of the odd neutron, creating transitions between similar Nilsson levels with lower Q_alpha values.

In either case, an island of stability does not represent nuclei with the longest half-lives but those which are significantly stabilised against fission by closed-shell effects.

[edit] Evidence for Z=114 closed proton shell

Whilst evidence for closed neutron shells can be deemed directly from the systematic variation of Q_alpha 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 ²⁸²112 (T_SF1/2 = 0.8 ms) and ²⁸⁶114 (T_SF1/2 = 130 ms), and ²⁸⁴112 (T_SF = 97 ms) and ²⁸⁸114 (T_SF >800 ms). Further evidence would come from the measurement of partial SF half-lives of nuclei with Z>114, such as ²⁹⁰116 and ²⁹²118 (both N=174 isotones). The extraction of Z=114 effects is complicated by the presence of a dominating N=184 effect in this region.

[edit] Difficulty in synthesis

The direct synthesis of ununquadium-298 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 quasi-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 reaction below may represent a method of synthesis:

20480Hg + 13654Xe → 298114Uuq + 4020Ca + 2 10n

It is also possible that ²⁹⁸114 can be synthesised 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 most likely be extremely small. One such reaction is:

24494Pu + 9640Zr → 338134Utq + 2 10n

338134Utq → 298114Uuq + 10 42He

[edit] Currently running experiments

In February 2009, it was indicated that the team at LBNL may have detected an atom of element 114 using the previously-studied reaction ²⁴²Pu + ⁴⁸Ca.^[19] Confirmation is not yet available.

In addition, in April 2009, the FLNR carried out another study of the chemistry of element 114. Results are not yet available.

In May 2009, the team at GSI began a study of the reaction between ²⁴⁴Pu and ⁴⁸Ca as a first step towards the synthesis of element 117.^[20]

[edit] Future experiments

The team at RIKEN have indicated plans to study the cold fusion reaction:

20882Pb + 7632Ge → 284114Uuq^* → ?

The FLNR have future plans to study light isotopes of element 114, formed in the reaction between ²³⁹Pu and ⁴⁸Ca.

[edit] See also

• Island of stability: Ununquadium–Unbinilium–Unbihexium
• Lead
• Periodic table (extended)
• Isotopes of ununquadium

[edit] References

[edit] External links

Wikimedia Commons has media related to: Ununquadium

• WebElements.com: Uuq
• First postcard from the island of nuclear stability
• Second postcard from the island of stability

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