Ununpentium

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

Most-stable 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 center of the theoretical island of stability. The most stable isotope of ununpentium is predicted to be Uup-299, containing the theorized "magic number" of 184 neutrons. The most neutron rich isotope to date is Uup-288, which contains only 173 neutrons.

1 Discovery profile
2 Naming
3 Electronic structure
4 Extrapolated chemical properties of eka-bismuth
- 4.1 Oxidation states
- 4.2 Chemistry
5 History of synthesis of isotopes by hot fusion
- 5.1 ²³⁸U(⁵¹V,xn)^289−xUup
- 5.2 ²⁴³Am(⁴⁸Ca,xn)^291−xUup (x=3,4)
6 Chronology of isotope discovery
7 Yields of isotopes
- 7.1 Hot fusion
8 Future experiments
9 See also
10 References
11 External links

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.^[1]^[2] 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.

$\,^{48}_{20}\mathrm{Ca} + \,^{243}_{95}\mathrm{Am} \to \,^{291}_{115}\mathrm{Uup} ^{*} \to \,^{287}_{113}\mathrm{Uut}$

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.^[3]^[4] Both the half-life and decay mode were confirmed for the proposed ²⁶⁸Db which lends support to the assignment of Z=115 to the parent nuclei.

Theoretical calculation in a quantum tunneling model supports the experimental alpha decay half-lives.^[5]

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

Electronic structure

Ununpentium has 6 full shells, 7s+5p+4d+2f=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.^[6]. B.L. Johnson supposes ununpentium to be dark metallic.

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−xUup

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.^[7]

²⁴³Am(⁴⁸Ca,xn)^291−xUup (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 ²⁸⁸Uup and a single atom of ²⁸⁷Uup. The reaction was studied further in June 2004 in an attempt to isolate the descendant ²⁶⁸Db from the ²⁸⁸Uup 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

$\,^{209}_{83}\mathrm{Bi} + \,^{76}_{32}\mathrm{Ge} \to \,^{285}_{115}\mathrm{Uuq} ^{*} \to \�?.$

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.