Unumpentium (115)

The essentials

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.

It is placed as a heavier homologue to bismuth and the heaviest member of group 15 (VA). It was first observed in 2003, following experiments carried out between 14 July and 10 August.   and about 50 atoms of ununpentium have been synthesized to date, with about 25 direct decays of the parent element having been detected. Four consecutive isotopes are currently known, ^287–290Uup, with ²⁸⁹Uup having the longest measured half-life of ~200 ms.  On August 27, 2013, researchers at GSI from Lund University in Sweden reported confirming the existence of the element. On September 10, 2013, researchers from the same research group working in Darmstadt, Germany reported synthesis as well.Only four nuclei were identified and the claim has not yet been ratified, but the results are now published in a reputable peer-reviewed journal (info below).

Name: Ununpentium Symbol: Uup Atomic number: 115 Atomic weight: [ 288 ] Standard state: presumably a solid at 298 K CAS Registry ID: 54085-64-2

Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 7 Block in periodic table: p-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Experimental results reported in 2004 involving the bombardment of americium-243 with calcium-48 ions are consistent with the formation in the laboratory of a few atoms of elements 113 and 115. In experiments conducted at the JINR U400 cyclotron with the Dubna gas-filled separator between July 14 and Aug. 10, 2003, atomic decay patterns were observed said to confirm the existence of element 115 and element 113. In these decay chains, element 113 is produced via the α-decay of element 115.

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:
"Experiments on the synthesis of element 115 in the reaction ²⁴³Am(⁴⁸Ca,xn)^291–x115",  
Yu. Ts. Oganessian, V. K. Utyonkoy, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov, I. V. Shirokovsky, Yu. S. Tsyganov, G. G. Gulbekian, S. L. Bogomolov, A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, A. A. Voinov, G. V. Buklanov, K. Subotic, V. I. Zagrebaev, M. G. Itkis, J. B. Patin, K. J. Moody, J. F. Wild, M. A. Stoyer, N. J. Stoyer, D. A. Shaughnessy, J. M. Kenneally, and R. W. Lougheed, Phys. Rev. C, 2004, 69, 021601(R)

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

Sergei Dmitriev from the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna, Russia, has formally put forward their claim of discovery of ununpentium to the IUPAC/IUPAP Joint Working Party (JWP). In 2011, the IUPAC evaluated the Dubna–Livermore results and concluded that they did not meet the criteria for discovery.

Naming

Ununpentium is historically known as eka-bismuth. Ununpentium is a temporary IUPAC systematic element name derived from the digits 115, where "un-" represents Latin unum. "Pent-" represents the Greek word for five.

Physical properties

• Melting point: 670 K; 400 C; 750 F
• Boiling point: ~1400 K; ~1100 C; ~2000 F
• Density of solid: 13000 (predicted) kg m^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d¹⁰.7s².7p³ (a guess based upon that of bismuth)
• Shell structure:  2.8.18.32.32.18.5
• Term symbol:   ⁴S_3/2 (a guess based upon guessed electronic structure)

Isolation

Currently, the identification of element 115 is yet to be confirmed by IUPAC, but the experiments leading to element 115 are now published in a prestigious peer reviewed journal. As only about four atoms of element 115 have ever been made (through nuclear reactions involving fusing calcium nuclei with americium nuclei) isolation of an observable quantity has never been achieved, and may well never be.

²⁴³₉₅Am + ⁴⁸₂₀Ca → ²⁸⁷₁₁₅Uup + 4 ¹n

²⁴³₉₅Am + ⁴⁸₂₀Ca → ²⁸⁸₁₁₅Uup + 3 ¹n

In these first experiments, three nuclei of the ²⁸⁸Uup isotope were made and one of the ²⁸⁷Uup isotope. All the nuclei formed decayed in less than a second by emitting α-particles. These decays resulted in isotopes of element 113 (mass number 283 or 284, containing 113 protons and either 170 or 171 neutrons). These isotopes of element 113 are also radioactive and underwent further α-decay processes to isotopes of element 111 and so on down to at least element 105 (dubnium).

²⁸⁷₁₁₅Uup → ²⁸³₁₁₃Uut + ⁴₂He (46.6 milliseconds)

²⁸⁸₁₁₅Uup → ²⁸⁴₁₁₃Uut + ⁴₂He (80.3 milliseconds)

²⁸⁸₁₁₅Uup → ²⁸⁴₁₁₃Uut + ⁴₂He (18.6 milliseconds)

²⁸⁸₁₁₅Uup → ²⁸⁴₁₁₃Uut + ⁴₂He (280 milliseconds)