Ununoctium (118)

The essentials

Experiments conducted at Dubna in Russia at the Flerov Laboratory of Nuclear Reactions (by workers from the Joint Institute for Nuclear Research in Russia and the Lawrence Livermore National Laboratory in the USA) indicate that element 118 (ununoctium, Uuo) was produced. Not too much though, one atom in the spring of 2002 and two more in 2005.

Name: Ununoctium Symbol: Uuo Atomic number: 118 Atomic weight: [ 294 ] Standard state: presumably a gas at 298 K CAS Registry ID: 54144-19-3

Group in periodic table: 18 Group name: Noble gas Period in periodic table: 7 Block in periodic table: p-block Color: unknown, but probably a colorless gas Classification: Non-metallic

Historical information

The first decay of atoms of ununoctium was observed at the Joint Institute for Nuclear Research (JINR) by Yuri Oganessian and his group in Dubna, Russia, in 2002. On October 9, 2006, researchers from JINR and Lawrence Livermore National Laboratory of California, US, working at the JINR in Dubna, announced that they had indirectly detected a total of three (possibly four) nuclei of ununoctium-294 (one or two in 2002 and two more in 2005) produced via collisions of californium-249 atoms and calcium-48 ions.

Radioactive decay pathway of the isotope ununoctium-294. The decay energy and average half-life is given for the parent isotope and each daughter isotope. The fraction of atoms undergoing spontaneous fission (SF) is given in green.

In 2011, IUPAC evaluated the 2006 results of the Dubna-Livermore collaboration and concluded: "The three events reported for the Z = 118 isotope have very good internal redundancy but with no anchor to known nuclei do not satisfy the criteria for discovery".

Because of the very small fusion reaction probability (the fusion cross section is ~0.3–0.6 pb or (3–6)×10⁻⁴¹ m²) the experiment took four months and involved a beam dose of 4×10¹⁹ calcium ions that had to be shot at the californium target to produce the first recorded event believed to be the synthesis of ununoctium. Nevertheless, researchers are highly confident that the results are not a false positive, since the chance that the detections were random events was estimated to be less than one part in 100000.

In the experiments, the alpha-decay of three atoms of ununoctium was observed. A fourth decay by direct spontaneous fission was also proposed. A half-life of 0.89 ms was calculated: 294 Uuo decays into 290 Lv by alpha decay. Since there were only three nuclei, the half-life derived from observed lifetimes has a large uncertainty: 0.89+1.07
−0.31 ms.

The identification of the 294Uuo nuclei was verified by separately creating the putative daughter nucleus 290Lv directly by means of a bombardment of 245 Cm with 48 Ca ions, and checking that the 290 Lv decay matched the decay chain of the 294 Uuo nuclei. The daughter nucleus 290 Lv is very unstable, decaying with a lifetime of 14 milliseconds into 286 Fl, which may experience either spontaneous fission or alpha decay into 282 Cn, which will undergo spontaneous fission.

In a quantum-tunneling model, the alpha decay half-life of 294 Uuo was predicted to be 0.66+0.23 −0.18 ms with the experimental Q-value published in 2004. Calculation with theoretical Q-values from the macroscopic-microscopic model of Muntian–Hofman–Patyk–Sobiczewski gives somewhat low but comparable results.

Physical properties

• Boiling point: ~350 K (extrapolated)
• Density of solid: 4.9 to 5.1 (extrapolated) g cm^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d¹⁰.7s².7p⁶ (a guess based upon that of radon)
• Shell structure:  2.8.18.32.32.18.8
• Term symbol:   ¹S₀ (a guess based upon guessed electronic structure)

Isolation

Experiments conducted at Dubna in Russia at the Flerov Laboratory of Nuclear Reactions (by workers from the Joint Institute for Nuclear Research in Russia and the Lawrence Livermore National Laboratory in the USA) indicate that element 118 (ununoctium, Uuo) was produced. Not too much though, one atom in the spring of 2002 and two more in 2005.

The 2002 experiment involved firing a beam of ⁴⁸₂₀Ca at ²⁴⁹₉₈Cf. The experiment took 4 months and involved a beam of 2.5 x 10¹⁹ calcium ions to produce the single event believed to be the synthesis of element 118 (ununoctium) as the ²⁹⁴₁₁₈Uuo isotope. Three neutrons are released during this process.

²⁴⁹₉₈Cf + ⁴⁸₂₀Ca → ²⁹⁴₁₁₈Uuo + 3¹n

This ununoctium isotope then loses three alpha particles in rapid succesion:

²⁹⁴₁₁₈Uuo → ²⁹⁰₁₁₆Lv + ⁴₂He (1.29 milliseconds)

²⁹⁰₁₁₆Lv → ²⁸⁶₁₁₄Fl + ⁴₂He (14.4 milliseconds)

²⁸⁶₁₁₄Fl → ²⁸²₁₁₂Uub + ⁴₂He (230 milliseconds)

The ²⁸²₁₁₂Cn species then undergoes spontaneous fission (denoted SF) to other species. An important part of this work was additional work synthesising isotopes of element 116 through irradiation of ²⁴⁵Cm (as opposed to ²⁴⁹Cm referred to above).

²⁴⁵₉₈Cf + ⁴⁸₂₀Ca → ²⁹⁰₁₁₆Lv + 3¹n

Earlier, a team of Berkeley Lab scientists announced in 1999 the observation of what appeared to be element 118 but retracted the claim after several confirmation experiments failed to reproduce the results. This means that the following apparently is wrong. In this work it was claimed that elements 118 and 116 were formed by accelerating a beam of krypton-86 (⁸⁶₃₆Kr) ions to an energy of 449 million electron volts and directing the beam onto targets of lead-208 (²⁰⁸₈₂Pb). After 11 days work, just three atoms of the new element were identified. The production rates for element 118 are approximately one in every 10¹² interactions.

²⁰⁸₈₂Pb + ⁸⁶₃₆Kr → ²⁹³₁₁₈Uuo + ¹n

Ununseptium (117)

The essentials

Ununseptium is the superheavy artificial chemical element with temporary symbol Uus and atomic number 117. The element, also known as eka-astatine or simply element 117 (MUCH easier to remember for the general populous), is the second-heaviest of all the elements that have been created so far and is the second-to-last element of the 7th period of the periodic table. Its discovery was first announced in 2010—synthesis was claimed in Dubna, Russia, by a joint Russian-American collaboration, thus making it the most recently discovered element. Another experiment in 2011 created one of its daughter isotopes directly, partially confirming the results of the discovery experiment, and the original experiment was repeated successfully in 2012. However, the IUPAC/IUPAP Joint Working Party (JWP), which is in charge of examining claims of discovery of superheavy elements, has made no comment yet on whether the element can be recognized as discovered. Once it is so recognized, it may receive a permanent name which will be suggested for the element by its discoverers; "ununseptium" is a temporary systematic element name that is intended to be used before a permanent one is established. It is commonly called "element 117" by researchers and in the literature instead of "ununseptium".

An article published in Physical Review Letters on 5 April 2010 (submitted 15 March 2010, "Synthesis of a new chemical element with atomic number Z=117", Joint Institute for Nuclear Research, RU-141980 Dubna, Russian Federation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA, University of Nevada Las Vegas, Las Vegas, Nevada 89154, USA, Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA, Lawrence Livemore National Laboratory, Livermore, California 94551, USA, and Research Institute of Atomic Reactors, RU-433510 Dimitrovgrad, Russian Federation) claims the identification of six atoms of the isotopes ²⁹³Uus (five atoms) and ²⁹⁴Uus (one atom) in fusion reactions between ⁴⁸Ca and ²⁴⁹Bk.

⁴⁸₂₀Ca + ²⁴⁹₉₇Bk → ²⁹⁷₁₁₇Uus* → ²⁹³₁₁₇Uus + 4 n

⁴⁸₂₀Ca + ²⁴⁹₉₇Bk → ²⁹⁷₁₁₇Uus* → ²⁹⁴₁₁₇Uus + 3 n

Decay chains involving eleven nuclei were identified by means of the Dubna Gas Filled Recoil Separator. It is said that the measured decay properties show a rise of stability for heavier isotopes with Z>=111, validating the concept of the "long sought island of enhanced stability for super-heavy nuclei".

The half-life for ²⁹³Uus is 0.014(+0.011-0.004) seconds and that for ²⁹⁴Uus is 0.078(+0.370-0.036) seconds. Each undergoes sequential decay chains down to ²⁸¹Rg and ²⁷⁰Db respectively.

In the periodic table, ununseptium is located in group 17, all previous members of which are halogens. However, ununseptium is likely to have significantly different properties from the halogens, although a few key properties such as the melting and boiling points, as well as the first ionization energy are expected to follow the periodic trends. 

Name: Ununseptium Symbol: Uus Atomic number: 117 Atomic weight: [ 294 ] Standard state: presumably a solid at 298 K CAS Registry ID: 87658-56-8	Group in periodic table: 17 Group name: Halogen Period in periodic table: 7 Block in periodic table: p-block Color: unknown, but probably metallic and dark in appearance Classification: Unknown

Historical information

In 2004 the Joint Institute for Nuclear Research (JINR) team in Dubna, Moscow Oblast, Russia proposed an experiment to synthesize element 117 (so-called for the 117 protons in its nucleus) that required fusing a berkelium (element 97) target and a calcium (element 20) beam. However, the team at the Oak Ridge National Laboratory in the United States, the world's only producer of berkelium, could not then provide any, citing a lack of production of the exotic material. Plans to synthesize element 117 were shelved temporarily in favor of the synthesis of element 118, which was produced by bombarding a californium target with calcium.

The Russian team desired to use berkelium, an element they could not access, because the isotope of calcium used in the beam, calcium-48, has 20 protons and 28 neutrons; it is the lightest stable or near-stable nucleus with such a neutron excess. The second-lightest such nucleus, zinc-68, is much heavier. Since ununseptium has 117 protons in its nucleus and calcium has 20, they thus needed to use berkelium, which has 97 protons in its nucleus. The beam is made in Russia by chemically extracting the small quantities of calcium-48 present in Earth's natural calcium. Thus the resulting nuclei become heavier and closer to the sought-after island of stability, a concept wherein some super-heavy atoms can be relatively stable. Sufficiently heavy nuclei have not been created as of 2013, however, and the synthesized isotopes tend to have fewer neutrons than those expected to be in the island of stability.

Decay chain of the ununseptium isotopes produced. The figures near the arrows describe the decay characteristics: half-life time and decay energy. For each couple of values, the upper one is obtained experimentally (in black) while the lower one is predicted theoretically (in blue).

In 2008, the American team re-launched a program of berkelium production, and the Russian team was contacted. The production resulted in 22 milligrams of berkelium, enough to perform the experiment. The berkelium was subsequently cooled in 90 days and chemically purified in another 90 days. The berkelium target had to be brought to Russia quickly: the half-life of the isotope of berkelium used (berkelium-249) is only 330 days, which means that after this period, half of it would no longer be berkelium. In fact, if the experiment had not begun in six months after the target's departure, it would have had to be canceled due to insufficient quantities of the quickly decaying berkelium. In summer 2009, the target was packed into five lead containers to be sent via a commercial flight from New York to Moscow.

The teams had to deal in advance with the bureaucratic barrier between the two countries to allow the target's timely journey to Russia. This, however, did not prevent such problems: Russian customs twice refused to let the target enter the country because of missing or incomplete paperwork. Even though it traveled over the Atlantic Ocean five times, the journey only took a few days in total. The berkelium was then transferred to Dimitrovgrad, Ulyanovsk Oblast to be fixed on a thin titanium film, and then to Dubna where it was installed in the JINR particle accelerator, the world's most powerful for the synthesis of superheavy elements.

The experiment began in June 2009 and, in January 2010, scientists at the Flerov Laboratory of Nuclear Reactions announced internally that they had succeeded in detecting the decay of a new element with atomic number 117 via two decay chains of an odd-odd isotope (undergoing 6 alpha decays before undergoing spontaneous fission) and of an odd-even one (3 alpha decays before fission). On April 9, 2010 an official report was released in the journal Physical Review Letters. It revealed that the isotopes mentioned in the previous chains referred to ²⁹⁴Uus and ²⁹³Uus, formed as follows:

None of ununseptium's daughter isotopes (decay products) were known before the actual synthesis of ununseptium; thus, there was no basis for a JWP discovery claim, much less for its recognition. Ununpentium-289, one of ununseptium's daughters, was created directly in 2011, instead of being created indirectly from the decay of ununseptium, yet it matched the claimed decay properties measured from the discovery of ununseptium. The discoverers did not, however, submit a claim for the discovery of ununseptium when JWP was reviewing claims of discoveries of trans-copernicium elements (elements beyond copernicium) in 2007–2011. The Dubna team repeated the experiment in 2012 successfully, and its results matched the results of previous experiments. The scientists have since filed a new element registration paper,  and a new JWP staffer is working on assigning priority of the claim

Physical properties

• Melting point: 573-773 K; 300-500 C; 572-932 F
• Boiling point: 823 K; 550 C; 1022 F
• Density of solid: 7.1-7.3 (predicted) g cm^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d¹⁰.7s².7p⁵ (a guess based upon that of astatine)
• Shell structure:  2.8.18.32.32.18.7
• Term symbol:   ²P_3/2 (a guess based upon guessed electronic structure)
•  First ionization energy: 742.9 kJ mol^-1 (predicted)

Isolation

An article published in Physical Review Letters on 5 April 2010 ("Synthesis of a new chemical element with atomic number Z=117") claims the identification of six atoms of the isotopes ²⁹³Uus (five atoms) and ²⁹⁴Uus (one atom) in fusion reactions between ⁴⁸Ca and ²⁴⁹Bk.

⁴⁸₂₀Ca + ²⁴⁹₉₇Bk → ²⁹⁷₁₁₇Uus* → ²⁹³₁₁₇Uus + 4 n

⁴⁸₂₀Ca + ²⁴⁹₉₇Bk → ²⁹⁷₁₁₇Uus* → ²⁹⁴₁₁₇Uus + 3 n

Decay chains involving eleven nuclei were identified by means of the Dubna Gas Filled Recoil Separator. It is said that the measured decay properties show a rise of stability for heavier isotopes with Z>=111, validating the concept of the "long sought island of enhanced stability for super-heavy nuclei".

The half-life for ²⁹³Uus is 0.014(+0.011-0.004) seconds and that for ²⁹⁴Uus is 0.078(+0.370-0.036) seconds. Each undergoes sequential decay chains down to ²⁸¹Rg and ²⁷⁰Db respectively.

Livermorium (116)

The essentials.

Livermorium is the synthetic superheavy element with the symbol Lv and atomic number 116. The name was adopted by IUPAC on May 30, 2012, after the Lawrence Livermore National Laboratory, in California.

It is placed as the heaviest member of group 16 (VIA) although a sufficiently stable isotope is not known at this time to allow chemical experiments to confirm its position as a heavier homologue to polonium.

It was first detected in 2000, when an isotope of livermorium, ²⁹²Lv, was identified in the reaction of ²⁴⁸Cm with ⁴⁸Ca. It is very short lived and decomposes to a known isotope of element 114, ²⁸⁸₁₁₄Fl. Since then, about 35 atoms of livermorium have been produced, either directly or as a decay product of ununoctium, belonging to the four neighboring isotopes with masses 290–293. The most stable isotope known is livermorium-293 with a half-life of ~60 milliseconds. 

Name: Livermorium Symbol: Lv Atomic number: 116 Atomic weight: [ 293 ] Standard state: presumably a solid at 298 K CAS Registry ID: 54100-71-9

Group in periodic table: 16 Group name: Chalcogen 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

On July 19, 2000, scientists at Dubna (JINR) detected a single decay from an atom of livermorium following the irradiation of a Cm-248 target with Ca-48 ions. The results were published in December 2000. This 10.54 MeV alpha-emitting activity was originally assigned to ²⁹²Lv due to the correlation of the daughter to previously assigned ²⁸⁸Fl. That assignment was later altered to ²⁸⁹Fl, and hence this activity was correspondingly changed to ²⁹³Lv. Two further atoms were reported by the institute during their second experiment between April–May 2001.

In the same experiment they also detected a decay chain which corresponded to the first observed decay of flerovium and assigned to ²⁸⁹Fl. This activity has not been observed again in a repeat of the same reaction. However, its detection in this series of experiments indicates the possibility of the decay of an isomer of livermorium, namely ^293bLv, or a rare decay branch of the already discovered isomer,^293aLv, in which the first alpha particle was missed. Further research is required to positively assign this activity.

The team repeated the experiment in April–May 2005 and detected 8 atoms of livermorium. The measured decay data confirmed the assignment of the discovery isotope as ²⁹³Lv. In this run, the team also observed ²⁹²Lv in the 4n channel for the first time.

In May 2009, the Joint Working Party reported on the discovery of copernicium and acknowledged the discovery of the isotope ²⁸³Cn. This implied the de facto discovery of livermorium, as ²⁹¹Lv (see below), from the acknowledgment of the data relating to the granddaughter ²⁸³Cn, although the actual discovery experiment may be determined as that above.

In 2011, the IUPAC evaluated the Dubna team results and accepted them as a reliable identification of element 116.

Results published on the 6th December 2000 concerning recent experiments at Dubna in Russia (involving workers from The Joint Institute for Nuclear Research, Dubna, Russian Federation; The Lawrence Livermore National Laboratory, California, USA; The Research Institute of Atomic Reactors, Dimitrovgrad, Russian Federation; and The State Enterprise Electrohimpribor, Lesnoy, Russian Federation) describe the decay of the isotope ²⁹²Uuh (produced in the reaction of ²⁴⁸Cm with ⁴⁸Ca) to ²⁹²Uuq.

²⁴⁸₉₆Cm + ⁴⁸₂₀Ca → ²⁹²₁₁₆Lv + 4 n

This decayed 47 milliseconds later as follows to a previously identified isotope of elements 114, flerovium, Fl.

²⁹²₁₁₆Lv → ²⁸⁸₁₁₄Fl + ⁴₂He

Physical properties

• Melting point: 637-780 K; 364-507 C; 687-944 F (extrapolated)
• Boiling point: 1035-1135 K; 762-862 C; 1403-1583 F (extrapolated)
• Density of solid: 12.9 (predicted) g cm^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d¹⁰.7s².7p⁴ (a guess based upon that of polonium)
• Shell structure:  2.8.18.32.32.18.6
• Term symbol:   ³P₂ (a guess based upon guessed electronic structure)

Isolation

Results published on the 6th December 2000 concerning recent experiments at Dubna in Russia (involving workers from The Joint Institute for Nuclear Research, Dubna, Russian Federation; The Lawrence Livermore National Laboratory, California, USA; The Research Institute of Atomic Reactors, Dimitrovgrad, Russian Federation; and The State Enterprise Electrohimpribor, Lesnoy, Russian Federation) describe the decay of the isotope ²⁹²Lv (produced in the reaction of ²⁴⁸Cm with ⁴⁸Ca) to ²⁹²Fl.

²⁴⁸₉₆Cm + ⁴⁸₂₀Ca → ²⁹²₁₁₆Lv + 4 n

This decayed 47 milliseconds later as follows to a previously identified isotope of element 114, Fl.

²⁹²₁₁₆Lv → ²⁸⁸₁₁₄Fl + ⁴₂He