Ununpentium

2008/9 Schools Wikipedia Selection. Related subjects: Chemical elements

115 ununquadium ← ununpentium → ununhexium Bi ↑ Uup ↓ (Uhp) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	ununpentium, Uup, 115
Element category	presumably poor metals
Group, Period, Block	15, 7, p
Standard atomic weight	[288] g·mol−1
Electron configuration	perhaps [Rn] 5f14 6d10 7s2 7p3 (guess based on bismuth)
Electrons per shell	2, 8, 18, 32, 32, 18, 5
CAS registry number	54085-64-2
Selected isotopes
Main article: Isotopes of ununpentium iso NA half-life DM DE ( MeV) DP 288Uup syn 87.5 ms α 10.46 284Uut 287Uup syn 32 ms α 10.59 283Uut
References

Ununpentium (pronounced /ˌjuːnənˈpɛntiəm/ or /ˌʌnənˈpɛntiəm/) 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.

Two isotopes are currently known, Uup-287 and Uup-288.

Element 115 also falls in the centre of the theoretical island of stability. The most stable isotope of ununpentium is predicted to be Uup-299, containing the " magic number" of 184 neutrons. The most neutron rich isotope to date is Uup-288, which contains only 173 neutrons.

Discovery profile

On February 2, 2004, synthesis of ununpentium was reported in Physical Review C by a team composed of Russian scientists at the Joint Institute for Nuclear Research in Dubna, and American scientists at the Lawrence Livermore National Laboratory. The team reported that they bombarded americium-243 with calcium-48 ions to produce four atoms of ununpentium. These atoms, they report, decayed by emission of alpha-particles to ununtrium in approximately 100 milliseconds.

The Dubna-Livermore collaboration has strengthened their claim for the discovery of ununpentium by conducting chemical experiments on the decay daughter ²⁶⁸Db. In experiments in June 2004 and December 2005, the Dubnium isotope was successfully identified by milking the Db fraction and measuring any SF activities. Both the halflife and decay mode were confirmed for the proposed ²⁶⁸Db which lends support to the assignment of Z=115 to the parent nuclei.

Naming

Current names

The element with Z=115 is historically known as eka-bismuth. Ununpentium (Uup) is a temporary IUPAC systematic element name. Research scientists usually refer to the element simply as element 115 (E115).

Proposed names by claimants

Claims to the discovery of element 115 have been put forward by Dmitriev of the Dubna team. The Joint Working Party will decide to whom the right to suggest a name will be given. The IUPAC have the final say on the official adoption of a name. The table below gives the names that the teams above have suggested and which can be verified by press interviews.

Disallowed names

According to IUPAC rules, names used for previous elements that have ultimately not been adopted are not allowed to be proposed for future use. The table below summarises those names which are probably not allowed to be proposed by the claimant laboratories under the rules.

Name	Symbol	Reason
Russium	Rs	Used for claimed discovery of element 43
Kurchatovium	Ku	Used for claimed discovery of element 104

Plausible names

Many speculative names appear in popular literature. The table below lists these names in the case where they obey IUPAC rules and are plausible with regard to the claimant laboratories. Rumoured suggestions (*) linked to the claimant laboratories are also included.

Suggested Name	Suggested Synbol	Derivation	Comments
Langevenium*	Ln	Langevin, prominent French nuclear physicist	Russian team unlikely to use a French physicist ?

Electronic structure

Ununpentium has 6 full shells, 7 s+5 p+4 d+2 f=18 full subshells, and 115 orbitals:

Bohr model: 2, 8, 18, 32, 32, 18, 5

Quantum mechanical model: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰ 4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰ 6p⁶7s²5f¹⁴6d¹⁰7p³

Extrapolated chemical properties of eka-bismuth

Oxidation states

Element 115 is projected to be the third member of the 7p series of non-metals and the heaviest member of group 15 (VA) in the Periodic Table, below bismuth. In this group, each member is known to portray the group oxidation state of +V but with differing stability. For nitrogen, the +V state is very difficult to achieve due to the lack of low-lying d- orbitals and the inability of the small nitrogen atom to accommodate five ligands. The +V state is well represented for phosphorus, arsenic, and antimony. However, for bismuth it is rare due to the reluctance of the 6s² electron to participate in bonding. This effect is known as the "inert pair effect" and is commonly linked to relativistic stabilisation of the 6s-orbitals. It is expected that element 115 will continue this trend and portray only +III and +I oxidation states. Nitrogen(I) and bismuth(I) are known but rare and Uup(I) is likely to show some unique properties.

Chemistry

It is expected that the chemistry of ununpentium will be related to its lighter homologue bismuth. In this regard it is expected to undergo oxidation only as far as the trioxide Uup₂O₃. Oxidation with the more reactive halogens should form the trihalides, such as UupF₃ and UupCl3. The less-oxidising, heavier halogens, may well only be able to promote the formation of the monohalides, UupBr and UupI.

History of synthesis of isotopes by hot fusion

²³⁸U(⁵¹V,xn)^289−x115

There are strong indications that this reaction was performed in late 2004 as part of a uranium(IV) fluoride target test at the GSI. No reports have been published suggesting that no products atoms were detected, as anticipated by the team.

²⁴³Am(⁴⁸Ca,xn)^291−x115 (x=3,4)

This reaction was first performed by the team in Dubna in July-August 2003. In two separate runs they were able to detect 3 atoms of ²⁸⁸115 and a single atom of ²⁸⁷115. The reaction was studied further in June 2004 in an attempt to isolate the descendant ²⁶⁸Db from the ²⁸⁸115 decay chain. After chemical separation of a +4/+5 fraction, 15 SF decays were measured with a lifetime consistent with ²⁶⁸Db. In order to prove that the decays were from dubnium-268, the team repeated the reaction in August 2005 and separated the +4 and +5 fractions and further separated the +5 fractions into tantalum-like and niobium-like ones. Five SF activities were observed, all occurring in the +5 fractions and none in the tantalum-like fractions, proving that the product was indeed isotopes of dubnium.

Chronology of isotope discovery

Isotope	Year discovered	Discoverer reaction
287Uup	2003	243Am(48Ca,4n)
288Uup	2003	243Am(48Ca,3n)

Yields of isotopes

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing ununpentium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile	Target	CN	2n	3n	4n	5n
48Ca	243Am	291Uup		3.7 pb, 39.0 MeV	0.9 pb, 44.4 MeV

Future experiments

The team at RIKEN are planning to study the reaction

As a primary next-goal for the Dubna team, they are planning to examine to products of the ²⁴³Am + ⁴⁸Ca using mass spectrometry in their state-of-the-art MASHA machine. They will attempt to isolate the dubnium products, convert them chemically into a volatile compound, most likely ²⁶⁸DbCl₅, and measure the mass directly.

In popular culture

UFO propulsion

Element 115 was first mentioned in the 1980s in association with UFO conspiracy theories. The most popular account of element 115 is from Bob Lazar, a scientist who claims to have worked on a top-secret, alien craft reverse-engineering program at a site known as S-4 near Groom Lake, Nevada. Many popular culture websites exist which discuss and critique the claims surrounding the element and the field.

Bob Lazar claims that Element 115 exists as a stable isotope. It's used as a fuel via nuclear reactions with proton projectiles in which antiprotons are created. These are then collected and channeled into an annihilation chamber where they react with protons to form gamma rays and lots of energy. This enormous power is used to fantastically multiply the minuscule Gravity-A wave also produced by the onboard Element 115 reactor.

Gravity-A is understood to exist only between atomic nuclear particles and is vastly more powerful than the Gravity-B with which we are all familiar from our own everyday experience. Element 115 is unusual in that the Gravity-A effect extends just beyond the perimeter of the Element 115 atom and with very advanced technology can be tapped and amplified and then directed via gravity distortion devices to produce a kind of "propulsive" effect for the alien spacecraft. What is supposedly happening is that the craft is creating a large enough space-time distortion along its direction of orientation that it essentially "falls downhill" through the artificially generated gravity corridor.

Science-based critique of claim

Stable E115

There is much debate regarding the possibility of a stable isotope of element 115. The element is expected to lie within the island of stability and recent results have confirmed its existence (see ununquadium). The recent synthesis of two isotopes of ununpentium has been taken to suggest that the existence of a stable isotope is unlikely. However, many critics fail to appreciate the nature of closed magic shells. In particular, most people focus solely on the much talked about N=184 shell. It should be pointed out that this is not the only closed magic neutron shell. Calculations have indicated a closed deformed magic shell at N=196 and a spherical closed shell at N=228. These calculations in conjunction with expected trends strongly imply that more stable isotopes of element 114 are possibly ³¹⁰114 (N=196) and most likely ³⁴²114 (N=226). Taking hindrance of fission by odd particles into account, the most stable isotope of element 115 is probably ³⁴⁵115 and definitely not ²⁹⁹115. Such nuclei also have much more favourable N/Z values and lie closer to the classical stability line.²⁹⁸114 is in fact relatively neutron deficient for a Z=114 nucleus (N/Z 2.61 c.f. 2.60 for ²⁴⁴Pu) using a classical liquid-drop approach. Using the trends in Q_alpha vs N from recent calculations, extrapolations indicate that Q_alpha should fall on approach to the N=228 shell and Q_alpha may reach a value of ~5.8 MeV for ³⁴²114. This provides a halflife of 1.83x10¹⁰ years (using Viola-Seaborg equation) and can be taken to be 'stable', like uranium.

Antiproton synthesis

The claimed method of synthesis of the antiprotons is known from the study of cosmic rays. Interactions between protons and nuclei lead to the formation of so-called secondary antiprotons which could be stored and used. The reaction would be inferred to be:

Annihilation

The study of the proton-antiproton annihilation reaction is well-known and is currently the subject of much research.

Levitation effects

Levitation in materials is caused by diamagnetic properties. Bismuth is known to be the strongest of all diamagnetic materials on Earth and hence element 115, as its heavier homolog, may well have even stronger diamagnetic attributes. Recent research on the synthesis of element 113 has highlighted the effect of the structure of the bismuth nucleus on reactions and as such it should be prone to manipulation using electrorotation. These levitation effects though do not have anything to do with gravity manipulation, as they are purely electromagnetic in nature. (diamagnetism is a form of magnetism, not gravity) That certain elements can have anomalous gravitational effects is unproven.

Summary

Some of the claimed properties of element 115 may have some verification from mainstream science, either as hard experimental evidence or in modern theoretical calculations. Others are either lacking or are the result of simple misunderstanding as in the case of the erroneously attributed claims of gravity manipulation properties.

Other

This element was used as fuel for a time machine in the Science fiction show Seven Days. It is also the most desired resource in the X-Com series of tactical computer games.