Tennessine

Tennessine is a synthetic chemical element with symbol Ts and atomic number 117. It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table.

The discovery of tennessine was officially announced in Dubna, Russia, by a Russian–American collaboration in April 2010, which makes it the most recently discovered element as of 2019. One of its daughter isotopes was created directly in 2011, partially confirming the results of the experiment. The experiment itself was repeated successfully by the same collaboration in 2012 and by a joint German–American team in May 2014. In December 2015, the Joint Working Party of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics, which evaluates claims of discovery of new elements, recognized the element and assigned the priority to the Russian–American team. In June 2016, the IUPAC published a declaration stating that the discoverers had suggested the name tennessine after Tennessee, United States.[a] In November 2016, they officially adopted the name "tennessine".

Tennessine may be located in the "island of stability", a concept that explains why some superheavy elements are more stable compared to an overall trend of decreasing stability for elements beyond bismuth on the periodic table. The synthesized tennessine atoms have lasted tens and hundreds of milliseconds. In the periodic table, tennessine is expected to be a member of group 17, all other members of which are halogens.[b] Some of its properties may significantly differ from those of the halogens due to relativistic effects. As a result, tennessine is expected to be a volatile metal that neither forms anions nor achieves high oxidation states. A few key properties, such as its melting and boiling points and its first ionization energy, are nevertheless expected to follow the periodic trends of the halogens.

Tennessine,  117Ts
Tennessine
Pronunciation/ˈtɛnɪsiːn/[1] (TEN-ə-seen)
Appearancesemimetallic (predicted)[2]
Mass number294 (most stable isotope)
Tennessine in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
At

Ts

(Usu)
livermoriumtennessineoganesson
Atomic number (Z)117
Groupgroup 17
Periodperiod 7
Blockp-block
Element category  unknown chemical properties, but probably a post-transition metal[3][4]
Electron configuration[Rn] 5f14 6d10 7s2 7p5 (predicted)[5]
Electrons per shell
2, 8, 18, 32, 32, 18, 7 (predicted)
Physical properties
Phase at STPunknown phase (predicted)[5][6]
Melting point623–823 K ​(350–550 °C, ​662–1022 °F) (predicted)[5]
Boiling point883 K ​(610 °C, ​1130 °F) (predicted)[5]
Density (near r.t.)7.1–7.3 g/cm3 (extrapolated)[6]
Atomic properties
Oxidation states(−1), (+1), (+3), (+5) (predicted)[2][5]
Ionization energies
  • 1st: 742.9 kJ/mol (predicted)[7]
  • 2nd: 1435.4 kJ/mol (predicted)[7]
  • 3rd: 2161.9 kJ/mol (predicted)[7]
  • (more)
Atomic radiusempirical: 138 pm (predicted)[6]
Covalent radius156–157 pm (extrapolated)[6]
Other properties
Natural occurrencesynthetic
CAS Number54101-14-3
History
Namingafter Tennessee region
DiscoveryJoint Institute for Nuclear Research, Lawrence Livermore National Laboratory, Vanderbilt University and Oak Ridge National Laboratory (2009)
Main isotopes of tennessine
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
293Ts[8] syn 22 ms α 289Mc
294Ts[9] syn 51 ms α 290Mc

History

Pre-discovery

In December 2004, the Joint Institute for Nuclear Research (JINR) team in Dubna, Moscow Oblast, Russia, proposed a joint experiment with the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, United States, to synthesize element 117—so-called for the 117 protons in its nucleus. Their proposal involved fusing a berkelium (element 97) target and a calcium (element 20) beam, conducted via bombardment of the berkelium target with calcium nuclei:[11] this would complete a set of experiments done at the JINR on the fusion of actinide targets with a calcium-48 beam, which had thus far produced the new elements 113116 and 118. The ORNL—then the world's only producer of berkelium—could not then provide the element, as they had temporarily ceased production,[11] and re-initiating it would be too costly.[12] Plans to synthesize element 117 were suspended in favor of the confirmation of element 118, which had been produced earlier in 2002 by bombarding a californium target with calcium.[13] The required berkelium-249 is a by-product in californium-252 production, and obtaining the required amount of berkelium was an even more difficult task than obtaining that of californium, as well as costly: it would cost around 3.5 million dollars, and the parties agreed to wait for a commercial order of californium production, from which berkelium could be extracted.[12][14]

The JINR team sought to use berkelium because calcium-48, the isotope of calcium used in the beam, has 20 protons and 28 neutrons, making a neutron–proton ratio of 1.4; and it is the lightest stable or near-stable nucleus with such a large neutron excess. The second-lightest such nucleus, palladium-110 (46 protons, 64 neutrons, neutron–proton ratio of 1.391), is much heavier. Thanks to the neutron excess, the resulting nuclei were expected to be heavier and closer to the sought-after island of stability.[c] Of the aimed for 117 protons, calcium has 20, and thus they needed to use berkelium, which has 97 protons in its nucleus.[15]

In February 2005, the leader of the JINR team—Yuri Oganessian—presented a colloquium at ORNL. Also in attendance were representatives of Lawrence Livermore National Laboratory, who had previously worked with JINR on the discovery of elements 113–116 and 118, and Joseph Hamilton of Vanderbilt University, a collaborator of Oganessian.[17]

Hamilton checked if the ORNL high-flux reactor produced californium for a commercial order: the required berkelium could be obtained as a by-product. He learned that it did not and there was no expectation for such an order in the immediate future. Hamilton kept monitoring the situation, making the checks once in a while. (Later, Oganessian referred to Hamilton as "the father of 117" for doing this work.)[17]

Discovery

ORNL resumed californium production in spring 2008. Hamilton noted the restart during the summer and made a deal on subsequent extraction of berkelium.[18] During a September 2008 symposium at Vanderbilt University in Nashville, Tennessee celebrating his 50th year on the Physics faculty, he introduced Oganessian to James Roberto (then the deputy director for science and technology at ORNL).[19] They established a collaboration among JINR, ORNL, and Vanderbilt;[14] the team at the Lawrence Livermore National Laboratory (LLNL) in Livermore, California, U.S., was soon invited to join.[20]

Berkelium
The berkelium target used for the synthesis (in solution)

In November 2008, the U.S. Department of Energy, which had oversight over the reactor in Oak Ridge, allowed the scientific use of the extracted berkelium.[20] The production lasted 250 days and ended in late December 2008,[21] resulting in 22 milligrams of berkelium, enough to perform the experiment.[22] In January 2009, the berkelium was removed from ORNL’s High Flux Isotope Reactor;[20] it was subsequently cooled for 90 days and then processed at ORNL’s Radiochemical Engineering and Development Center to separate and purify the berkelium material, which took another 90 days.[14] Its half-life is only 330 days: after that time, half the berkelium produced would have decayed. Because of this, the berkelium target had to be quickly transported to Russia; for the experiment to be viable, it had to be completed within six months of its departure from the United States.[14] The target was packed into five lead containers to be flown from New York to Moscow.[14]

Russian customs officials twice refused to let the target enter the country because of missing or incomplete paperwork. Over the span of a few days, the target traveled over the Atlantic Ocean five times.[14] On its arrival in Russia in June 2009, the berkelium was transferred to Research Institute of Atomic Reactors (RIAR) in Dimitrovgrad, Ulyanovsk Oblast, where it was deposited as a 300-nanometer-thin layer on a titanium film.[21] In July 2009, it was then transported to Dubna,[21] where it was installed in the particle accelerator at JINR.[22] The calcium-48 beam was generated by chemically extracting the small quantities of calcium-48 present in naturally occurring calcium,[23] enriching it 500 times. This work was done in the closed town of Lesnoy, Sverdlovsk Oblast, Russia.[20]

The experiment began late July 2009.[20] In January 2010, scientists at the Flerov Laboratory of Nuclear Reactions announced internally that they had detected the decay of a new element with atomic number 117 via two decay chains: one of an odd-odd isotope undergoing 6 alpha decays before spontaneous fission, and one of an odd-even isotope undergoing 3 alpha decays before fission.[24] The obtained data from the experiment was sent to the LLNL for further analysis.[25] On April 9, 2010, an official report was released in the journal Physical Review Letters identifying the isotopes as 294117 and 293117, which were shown to have half-lives on the order of tens or hundreds of milliseconds. The work was signed by all parties involved in the experiment to some extent: JINR, ORNL, LLNL, RIAR, Vanderbilt, the University of Tennessee, and the University of Nevada (Las Vegas, Nevada, U.S.), which provided data analysis support.[26] The isotopes were formed as follows:[27][d]

249
97
Bk
+ 48
20
Ca
297117* → 294117 + 3 1
0

n
(1 event)
249
97
Bk
+ 48
20
Ca
297117* → 293117 + 4 1
0

n
(5 events)

Confirmation

DecayChain Ununseptium
Decay chain of the atoms produced in the original experiment. The figures near the arrows describe experimental (black) and theoretical (blue) values for the half-life and energy of each decay.[27]

All daughter isotopes (decay products) of element 117 were previously unknown;[27] therefore, their properties could not be used to confirm the claim of discovery. In 2011, when one of the decay products (289115) was synthesized directly, its properties matched those measured in the claimed indirect synthesis from the decay of element 117.[28] The discoverers did not submit a claim for their findings in 2007–2011 when the Joint Working Party was reviewing claims of discoveries of new elements.[29]

The Dubna team repeated the experiment in 2012, creating seven atoms of element 117 and confirming their earlier synthesis of element 118 (produced after some time when a significant quantity of the berkelium-249 target had beta decayed to californium-249). The results of the experiment matched the previous outcome;[9] the scientists then filed an application to register the element.[30] In May 2014, a joint German–American collaboration of scientists from the ORNL and the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Hessen, Germany, claimed to have confirmed discovery of the element.[8][31] The team repeated the Dubna experiment using the Darmstadt accelerator, creating two atoms of element 117.[8]

In December 2015, the JWP officially recognized the discovery of 293117 on account of the confirmation of the properties of its daughter 289115,[32] and thus the listed discoverers—JINR, LLNL, and ORNL—were given the right to suggest an official name for the element. (Vanderbilt was left off the initial list of discoverers in an error that was later corrected.)[30][33]

In May 2016, Lund University (Lund, Scania, Sweden) and GSI cast some doubt on the syntheses of elements 115 and 117. The decay chains assigned to 289115, the isotope instrumental in the confirmation of the syntheses of elements 115 and 117, were found to be too different to belong to the same nuclide with a reasonably high probability. The reported 293117 decay chains approved as such by the JWP were found to require splitting into individual data sets assigned to different isotopes of element 117. It was also found that the claimed link between the decay chains reported as from 293117 and 289115 probably did not exist. (On the other hand, the chains from the non-approved isotope 294117 were found to be congruent.) The multiplicity of states found when nuclides that are not even–even undergo alpha decay is not unexpected and contributes to the lack of clarity in the cross-reactions. This study criticized the JWP report for overlooking subtleties associated with this issue, and noted that the fact that the only argument for the acceptance of the discoveries of elements 115 and 117 was an almost certainly non-existent link was "problematic".[34][35]

On June 8, 2017, two members of the Dubna team published a journal article answering these criticisms, analysing their data on the nuclides 293117 and 289115 with widely accepted statistical methods, noted that the 2016 studies indicating non-congruence produced problematic results when applied to radioactive decay: they excluded from the 90% confidence interval both average and extreme decay times, and the decay chains that would be excluded from the 90% confidence interval they chose were more probable to be observed than those that would be included. The 2017 reanalysis concluded that the observed decay chains of 293117 and 289115 were consistent with the assumption that only one nuclide was present at each step of the chain, although it would be desirable to be able to directly measure the mass number of the originating nucleus of each chain as well as the excitation function of the 243Am+48Ca reaction.[36]

Naming

CorneliusVanderbiltStatue
Main campus of Hamilton's workplace of Vanderbilt University, one of the institutions named as co-discoverers of tennessine

Using Mendeleev's nomenclature for unnamed and undiscovered elements, element 117 should be known as eka-astatine. Using the 1979 recommendations by the International Union of Pure and Applied Chemistry (IUPAC), the element was temporarily called ununseptium (symbol Uus) until its discovery was confirmed and a permanent name chosen; the temporary name was formed from Latin roots "one", "one", and "seven", a reference to the element's atomic number of 117.[37] Many scientists in the field called it "element 117", with the symbol E117, (117), or 117.[5] According to guidelines of IUPAC valid at the moment of the discovery approval, the permanent names of new elements should have ended in "-ium"; this included element 117, even if the element was a halogen, which traditionally have names ending in "-ine";[38] however, the new recommendations published in 2016 recommended using the "-ine" ending for all new group 17 elements.[39] The IUPAC guidelines specify that the discovery team has naming rights for the element.

After the original synthesis in 2010, Dawn Shaughnessy of LLNL and Oganessian declared that naming was a sensitive question, and it was avoided as far as possible.[40] However, Hamilton declared that year, "I was crucial in getting the group together and in getting the 249Bk target essential for the discovery. As a result of that, I’m going to get to name the element. I can’t tell you the name, but it will bring distinction to the region."[26] (Hamilton teaches at Vanderbilt University in Nashville, Tennessee, U.S.)

In March 2016, the discovery team agreed on a conference call involving representatives from the parties involved on the name "tennessine" for element 117.[17] In June 2016, IUPAC published a declaration stating the discoverers had submitted their suggestions for naming the new elements 115, 117, and 118 to the IUPAC; the suggestion for the element 117 was tennessine, with a symbol of Ts, after "the region of Tennessee".[a] The suggested names were recommended for acceptance by the IUPAC Inorganic Chemistry Division; formal acceptance was set to occur after a five-months term following publishing of the declaration expires.[41] In November 2016, the names, including tennessine, were formally accepted. Concerns that the proposed symbol Ts may clash with a notation for the tosyl group used in organic chemistry were rejected, following existing symbols bearing such dual meanings: Ac (actinium and acetyl) and Pr (praseodymium and propyl).[42] The naming ceremony for moscovium, tennessine, and oganesson was held in March 2017 at the Russian Academy of Sciences in Moscow; a separate ceremony for tennessine alone had been held at ORNL in January 2017.[43]

Predicted properties

Nuclear stability and isotopes

The stability of nuclei quickly decreases with the increase in atomic number after curium, element 96, whose half-life is four orders of magnitude longer than that of any subsequent element. All isotopes with an atomic number above 101 undergo radioactive decay with half-lives of less than 30 hours. No elements with atomic numbers above 82 (after lead) have stable isotopes.[44] This is because of the ever-increasing Coulomb repulsion of protons, so that the strong nuclear force cannot hold the nucleus together against spontaneous fission for long. Calculations suggest that in the absence of other stabilizing factors, elements with more than 104 protons should not exist.[45] However, researchers in the 1960s suggested that the closed nuclear shells around 114 protons and 184 neutrons should counteract this instability, creating an "island of stability" where nuclides could have half-lives reaching thousands or millions of years. While scientists have still not reached the island, the mere existence of the superheavy elements (including tennessine) confirms that this stabilizing effect is real, and in general the known superheavy nuclides become exponentially longer-lived as they approach the predicted location of the island.[46][47] Tennessine is the second-heaviest element created so far, and all its known isotopes have half-lives of less than one second. Nevertheless, this is longer than the values predicted prior to their discovery.[27] The Dubna team believes that the synthesis of the element is direct experimental proof of the existence of the island of stability.[48]

Island of Stability derived from Zagrebaev
A chart of nuclide stability as used by the Dubna team in 2010. Characterized isotopes are shown with borders. According to the discoverers, the synthesis of element 117 serves as definite proof of the existence of the "island of stability" (circled).[48]

It has been calculated that the isotope 295Ts would have a half-life of about 18 milliseconds, and it may be possible to produce this isotope via the same berkelium–calcium reaction used in the discoveries of the known isotopes, 293Ts and 294Ts. The chance of this reaction producing 295Ts is estimated to be, at most, one-seventh the chance of producing 294Ts.[49][50][51] Calculations using a quantum tunneling model predict the existence of several isotopes of tennessine up to 303Ts. The most stable of these is expected to be 296Ts with an alpha-decay half-life of 40 milliseconds.[52] A liquid drop model study on the element's isotopes shows similar results; it suggests a general trend of increasing stability for isotopes heavier than 301Ts, with partial half-lives exceeding the age of the universe for the heaviest isotopes like 335Ts when beta decay is not considered.[53] Lighter isotopes of tennessine may be produced in the 243Am+50Ti reaction, which was considered as a contingency plan by the Dubna team in 2008 if 249Bk proved unavailable,[54] and may be studied again in the near future (2017–2018) to investigate the properties of nuclear reactions with a titanium-50 beam, which becomes necessary to synthesize elements beyond oganesson.[55]

Atomic and physical

Tennessine is expected to be a member of group 17 in the periodic table, below the five halogens; fluorine, chlorine, bromine, iodine, and astatine, each of which has seven valence electrons with a configuration of ns2np5.[56][e] For tennessine, being in the seventh period (row) of the periodic table, continuing the trend would predict a valence electron configuration of 7s27p5,[5] and it would therefore be expected to behave similarly to the halogens in many respects that relate to this electronic state. However, going down group 17, the metallicity of the elements increases; for example, iodine already exhibits a metallic luster in the solid state, and astatine is often classified as a metalloid due to its properties being quite far from those of the four previous halogens. As such, an extrapolation based on periodic trends would predict tennessine to be a rather volatile post-transition metal.[4]

Valence atomic energy levels for Cl, Br, I, At, and 117
Atomic energy levels of outermost s, p, and d electrons of chlorine (d orbitals not applicable), bromine, iodine, astatine, and tennessine

Calculations have confirmed the accuracy of this simple extrapolation, although experimental verification of this is currently impossible as the half-lives of the known tennessine isotopes are too short.[4] Significant differences between tennessine and the previous halogens are likely to arise, largely due to spin–orbit interaction — the mutual interaction between the motion and spin of electrons. The spin–orbit interaction is especially strong for the superheavy elements because their electrons move faster — at velocities comparable to the speed of light — than those in lighter atoms.[57] In tennessine atoms, this lowers the 7s and the 7p electron energy levels, stabilizing the corresponding electrons, although two of the 7p electron energy levels are more stabilized than the other four.[58] The stabilization of the 7s electrons is called the inert pair effect; the effect that separates the 7p subshell into the more-stabilized and the less-stabilized parts is called subshell splitting. Computational chemists understand the split as a change of the second (azimuthal) quantum number l from 1 to 1/2 and 3/2 for the more-stabilized and less-stabilized parts of the 7p subshell, respectively.[59][f] For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s2
7p2
1/2
7p3
3/2
.[5]

Differences for other electron levels also exist. For example, the 6d electron levels (also split in two, with four being 6d3/2 and six being 6d5/2) are both raised, so they are close in energy to the 7s ones,[58] although no 6d electron chemistry has been predicted for tennessine. The difference between the 7p1/2 and 7p3/2 levels is abnormally high; 9.8 eV.[58] Astatine's 6p subshell split is only 3.8 eV,[58] and its 6p1/2 chemistry has already been called "limited".[60] These effects cause tennessine's chemistry to differ from those of its upper neighbors (see below).

Tennessine's first ionization energy—the energy required to remove an electron from a neutral atom—is predicted to be 7.7 eV, lower than those of the halogens, again following the trend.[5] Like its neighbors in the periodic table, tennessine is expected to have the lowest electron affinity—energy released when an electron is added to the atom—in its group; 2.6 or 1.8 eV.[5] The electron of the hypothetical hydrogen-like tennessine atom—oxidized so it has only one electron, Ts116+—is predicted to move so quickly that its mass is 1.9 times that of a non-moving electron, a feature attributable to relativistic effects. For comparison, the figure for hydrogen-like astatine is 1.27 and the figure for hydrogen-like iodine is 1.08.[61] Simple extrapolations of relativity laws indicate a contraction of atomic radius.[61] Advanced calculations show that the radius of an tennessine atom that has formed one covalent bond would be 165 pm, while that of astatine would be 147 pm.[62] With the seven outermost electrons removed, tennessine is finally smaller; 57 pm[5] for tennessine and 61 pm[63] for astatine.

The melting and boiling points of tennessine are not known; earlier papers predicted about 350–500 °C and 550 °C, respectively,[5] or 350–550 °C and 610 °C, respectively.[64] These values exceed those of astatine and the lighter halogens, following periodic trends. A later paper predicts the boiling point of tennessine to be 345 °C[65] (that of astatine is estimated as 309 °C,[66] 337 °C,[67] or 370 °C,[68] although experimental values of 230 °C[69] and 411 °C[63] have been reported). The density of tennessine is expected to be between 7.1 and 7.3 g/cm3, continuing the trend of increasing density among the halogens; that of astatine is estimated to be between 6.2 and 6.5 g/cm3.[6]

Chemical

T-shaped-3D-balls
IF
3
has a T-shape configuration.
Trigonal-3D-balls
TsF
3
is predicted to have a trigonal configuration.

The known isotopes of tennessine, 293Ts and 294Ts, are too short-lived to allow for chemical experimentation at present. Nevertheless, many chemical properties of tennessine have been calculated.[70] Unlike the previous group 17 elements, tennessine may not exhibit the chemical behavior common to the halogens.[10] For example, fluorine, chlorine, bromine, and iodine routinely accept an electron to achieve the more stable electronic configuration of a noble gas, obtaining eight electrons (octet) in their valence shells instead of seven.[71] This ability weakens as atomic weight increases going down the group; tennessine would be the least willing group 17 element to accept an electron. Of the oxidation states it is predicted to form, −1 is expected to be the least common.[5] The standard reduction potential of the Ts/Ts couple is predicted to be −0.25 V; this value is negative and thus tennessine should not be reduced to the −1 oxidation state under standard conditions, unlike all the previous halogens.[2]

There is another opportunity for tennessine to complete its octet—by forming a covalent bond. Like the halogens, when two tennessine atoms meet they are expected to form a Ts–Ts bond to give a diatomic molecule. Such molecules are commonly bound via single sigma bonds between the atoms; these are different from pi bonds, which are divided into two parts, each shifted in a direction perpendicular to the line between the atoms, and opposite one another rather than being located directly between the atoms they bind. Sigma bonding has been calculated to show a great antibonding character in the At2 molecule and is not as favorable energetically. Tennessine is predicted to continue the trend; a strong pi character should be seen in the bonding of Ts2.[5][72] The molecule tennessine chloride (TsCl) is predicted to go further, being bonded with a single pi bond.[72]

Aside from the unstable −1 state, three more oxidation states are predicted; +5, +3, and +1. The +1 state should be especially stable because of the destabilization of the three outermost 7p3/2 electrons, forming a stable, half-filled subshell configuration;[5] astatine shows similar effects.[73] The +3 state should be important, again due to the destabilized 7p3/2 electrons.[64] The +5 state is predicted to be uncommon because the 7p1/2 electrons are oppositely stabilized.[5] The +7 state has not been shown—even computationally—to be achievable. Because the 7s electrons are greatly stabilized, it has been hypothesized that tennessine effectively has only five valence electrons.[74]

The simplest possible tennessine compound would be the monohydride, TsH. The bonding is expected to be provided by a 7p3/2 electron of tennessine and the 1s electron of hydrogen. The non-bonding nature of the 7p1/2 spinor is because tennessine is expected not to form purely sigma or pi bonds.[75] Therefore, the destabilized (thus expanded) 7p3/2 spinor is responsible for bonding.[76] This effect lengthens the TsH molecule by 17 picometers compared with the overall length of 195 pm.[75] Since the tennessine p electron bonds are two-thirds sigma, the bond is only two-thirds as strong as it would be if tennessine featured no spin–orbit interactions.[75] The molecule thus follows the trend for halogen hydrides, showing an increase in bond length and a decrease in dissociation energy compared to AtH.[5] The molecules TlTs and NhTs may be viewed analogously, taking into account an opposite effect shown by the fact that the element's p1/2 electrons are stabilized. These two characteristics result in a relatively small dipole moment (product of difference between electric charges of atoms and displacement of the atoms) for TlTs; only 1.67 D,[g] the positive value implying that the negative charge is on the tennessine atom. For NhTs, the strength of the effects are predicted to cause a transfer of the electron from the tennessine atom to the nihonium atom, with the dipole moment value being −1.80 D.[78] The spin–orbit interaction increases the dissociation energy of the TsF molecule because it lowers the electronegativity of tennessine, causing the bond with the extremely electronegative fluorine atom to have a more ionic character.[75] Tennessine monofluoride should feature the strongest bonding of all group 17 monofluorides.[75]

VSEPR theory predicts a bent-T-shaped molecular geometry for the group 17 trifluorides. All known halogen trifluorides have this molecular geometry and have a structure of AX3E2—a central atom, denoted A, surrounded by three ligands, X, and two unshared electron pairs, E. If relativistic effects are ignored, TsF3 should follow its lighter congeners in having a bent-T-shaped molecular geometry. More sophisticated predictions show that this molecular geometry would not be energetically favored for TsF3, predicting instead a trigonal planar molecular geometry (AX3E0). This shows that VSEPR theory may not be consistent for the superheavy elements.[74] The TsF3 molecule is predicted to be significantly stabilized by spin–orbit interactions; a possible rationale may be the large difference in electronegativity between tennessine and fluorine, giving the bond a partially ionic character.[74]

Notes

  1. ^ a b The declaration by the IUPAC mentioned "the contribution of the Tennessee region (emphasis added), including Oak Ridge National Laboratory, Vanderbilt University, and the University of Tennessee at Knoxville, to superheavy element research, including the production and chemical separation of unique actinide target materials for superheavy element synthesis at ORNL’s High Flux Isotope Reactor (HFIR) and Radiochemical Engineering Development Center (REDC)".
  2. ^ The term "group 17" refers to a column in the periodic table starting with fluorine and is distinct from "halogen", which relates to a common set of chemical and physical properties shared by fluorine, chlorine, bromine, iodine, and astatine, all of which precede tennessine in group 17. Unlike the other group 17 members, tennessine may not be a halogen.[10]
  3. ^ Although stable isotopes of the lightest elements usually have a neutron–proton ratio close or equal to one (for example, the only stable isotope of aluminium has 13 protons and 14 neutrons,[15] making a neutron–proton ratio of 1.077), stable isotopes of heavier elements have higher neutron–proton ratios, increasing with the number of protons. For example, iodine's only stable isotope has 53 protons and 74 neutrons, giving neutron–proton ratio of 1.396, gold's only stable isotope has 79 protons and 118 neutrons, yielding a neutron–proton ratio of 1.494, and plutonium's most stable isotope has 94 protons and 150 neutrons, and a neutron–proton ratio of 1.596.[15] This trend[16] is expected to make it difficult to synthesize the most stable isotopes of super-heavy elements as the neutron–proton ratios of the elements they are synthesized from will be too low.
  4. ^ A nuclide is commonly denoted by the chemical element's symbol immediately preceded by the mass number as a superscript and the atomic number as a subscript. Neutrons are represented as nuclides with atomic mass 1, atomic number 0, and symbol n. Outside the context of nuclear equations, the atomic number is sometimes omitted. An asterisk denotes an extremely short-lived (or even non-existent) intermediate stage of the reaction.
  5. ^ The letter n stands for the number of the period (horizontal row in the periodic table) the element belongs to. The letters "s" and "p" denote the s and p atomic orbitals, and the subsequent superscript numbers denote the numbers of electrons in each. Hence the notation ns2np5 means that the valence shells of lighter group 17 elements are composed of two s electrons and five p electrons, all located in the outermost electron energy level.
  6. ^ The quantum number corresponds to the letter in the electron orbital name: 0 to s, 1 to p, 2 to d, etc. See azimuthal quantum number for more information.
  7. ^ For comparison, the values for the ClF, HCl, SO, HF, and HI molecules are 0.89 D, 1.11 D, 1.55 D, 1.83 D, and 1.95 D. Values for molecules which do not form at standard conditions, namely GeSe, SnS, TlF, BaO, and NaCl, are 1.65 D, ~3.2 D, 4.23 D, 7.95 D, and 9.00 D.[77]

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Bibliography

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-ine

-ine is a suffix used in chemistry to denote two kinds of substance. The first is a chemically basic and alkaloidal substance. It was proposed by Joseph Louis Gay-Lussac in an editorial accompanying a paper by Friedrich Sertürner describing the isolation of the alkaloid "morphium", which was subsequently renamed to "morphine". Examples include quinine, morphine and guanidine. The second usage is to denote a hydrocarbon of the second degree of unsaturation. Examples include hexine and heptine. With simple hydrocarbons, this usage is identical to the IUPAC suffix -yne.

The suffix is usually pronounced either or depending on the word it appears in and the accent of the speaker. In a few words (for example, quinine and strychnine), the sound is normal in some accents. Gasoline ends with ; glycerine more often with than with .

It is noteworthy also that some elements of the periodic table (namely the halogens, in the Group 17) have this suffix: fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At), ending which was continued in the artificially created tennessine (Ts).

The suffix -in () is etymologically related and overlaps in usage with -ine. Many proteins and lipids have names ending with -in: for example, the enzymes pepsin and trypsin, the hormones insulin and gastrin, and the lipids stearin (stearine) and olein.

Berkelium

Berkelium is a transuranic radioactive chemical element with symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

The major isotope of berkelium, 249Bk, is synthesized in minute quantities in dedicated high-flux nuclear reactors, mainly at the Oak Ridge National Laboratory in Tennessee, USA, and at the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. The production of the second-most important isotope 247Bk involves the irradiation of the rare isotope 244Cm with high-energy alpha particles.

Just over one gram of berkelium has been produced in the United States since 1967. There is no practical application of berkelium outside scientific research which is mostly directed at the synthesis of heavier transuranic elements and transactinides. A 22 milligram batch of berkelium-249 was prepared during a 250-day irradiation period and then purified for a further 90 days at Oak Ridge in 2009. This sample was used to synthesize the new element tennessine for the first time in 2009 at the Joint Institute for Nuclear Research, Russia, after it was bombarded with calcium-48 ions for 150 days. This was the culmination of the Russia–US collaboration on the synthesis of the heaviest elements on the periodic table.

Berkelium is a soft, silvery-white, radioactive metal. The berkelium-249 isotope emits low-energy electrons and thus is relatively safe to handle. It decays with a half-life of 330 days to californium-249, which is a strong emitter of ionizing alpha particles. This gradual transformation is an important consideration when studying the properties of elemental berkelium and its chemical compounds, since the formation of californium brings not only chemical contamination, but also free-radical effects and self-heating from the emitted alpha particles.

Darmstadt

Darmstadt (German pronunciation: [ˈdaɐ̯mʃtat] (listen)) is a city in the state of Hesse in Germany, located in the southern part of the Rhine-Main-Area (Frankfurt Metropolitan Region). Darmstadt had a population of around 157,437 at the end of 2016. The Darmstadt Larger Urban Zone has 430,993 inhabitants.Darmstadt holds the official title "City of Science" (German: Wissenschaftsstadt) as it is a major centre of scientific institutions, universities, and high-technology companies. The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and the European Space Operations Centre (ESOC) are located in Darmstadt, as well as GSI Centre for Heavy Ion Research, where several chemical elements such as bohrium (1981), meitnerium (1982), hassium (1984), darmstadtium (1994), roentgenium (1994), and copernicium (1996) were discovered. The existence of the following elements were also confirmed at GSI Centre for Heavy Ion Research: nihonium (2012), flerovium (2009), moscovium (2012), livermorium (2010), and tennessine (2012). The Facility for Antiproton and Ion Research (FAIR) is an international accelerator facility under construction. Darmstadt is also the seat of the world's oldest pharmaceutical company, Merck, which is the city's largest employer.

Darmstadt was formerly the capital of a sovereign country, the Grand Duchy of Hesse and its successor, the People's State of Hesse, a federal state of Germany. As the capital of an increasingly prosperous duchy, the city gained some international prominence and remains one of the wealthiest cities in Europe. In the 20th century, industry (especially chemicals), as well as large science and electronics (later information technology) sectors became increasingly important, and are still a major part of the city's economy. It is also home to the football club SV Darmstadt 98.

Group 8 element

Group 8 is a group of chemical element in the periodic table. It consists of iron (Fe), ruthenium (Ru), osmium (Os) and hassium (Hs). They are all transition metals. Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior.

"Group 8" is the modern IUPAC name for this group; the old style name was group VIIIB in the CAS, US system or group VIIIA in the old IUPAC, European system.

Group 8 should not be confused with the old-style group name of VIIIA by CAS/US naming. That group is now called group 18.

Group 9 element

Group 9, numbered by IUPAC nomenclature, is a group of chemical element in the periodic table. Members are cobalt (Co), rhodium (Rh), iridium (Ir) and perhaps also the chemically uncharacterized meitnerium (Mt). These are all transition metals in the d-block. All known isotopes of meitnerium are radioactive with short half-lives, and it is not known to occur in nature; only minute quantities have been synthesized in laboratories.

Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior; however, rhodium deviates from the pattern.

Halogen

The halogens () are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (tennessine, Ts) may also be a halogen. In the modern IUPAC nomenclature, this group is known as group 17. The symbol X is often used generically to refer to any halogen.

The name "halogen" means "salt-producing". When halogens react with metals they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide.

The group of halogens is the only periodic table group that contains elements in three of the main states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens, that is chlorine, bromine and iodine, are often used as disinfectants. Organobromides are the most important class of flame retardants. Elemental halogens are dangerous and can be lethally toxic.

Heavy metals

Heavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. More specific definitions have been published, but none of these have been widely accepted. The definitions surveyed in this article encompass up to 96 out of the 118 known chemical elements; only mercury, lead and bismuth meet all of them. Despite this lack of agreement, the term (plural or singular) is widely used in science. A density of more than 5 g/cm3 is sometimes quoted as a commonly used criterion and is used in the body of this article.

The earliest known metals—common metals such as iron, copper, and tin, and precious metals such as silver, gold, and platinum—are heavy metals. From 1809 onwards, light metals, such as magnesium, aluminium, and titanium, were discovered, as well as less well-known heavy metals including gallium, thallium, and hafnium.

Some heavy metals are either essential nutrients (typically iron, cobalt, and zinc), or relatively harmless (such as ruthenium, silver, and indium), but can be toxic in larger amounts or certain forms. Other heavy metals, such as cadmium, mercury, and lead, are highly poisonous. Potential sources of heavy metal poisoning include mining, tailings, industrial wastes, agricultural runoff, occupational exposure, paints and treated timber.

Physical and chemical characterisations of heavy metals need to be treated with caution, as the metals involved are not always consistently defined. As well as being relatively dense, heavy metals tend to be less reactive than lighter metals and have much less soluble sulfides and hydroxides. While it is relatively easy to distinguish a heavy metal such as tungsten from a lighter metal such as sodium, a few heavy metals, such as zinc, mercury, and lead, have some of the characteristics of lighter metals, and, lighter metals such as beryllium, scandium, and titanium, have some of the characteristics of heavier metals.

Heavy metals are relatively scarce in the Earth's crust but are present in many aspects of modern life. They are used in, for example, golf clubs, cars, antiseptics, self-cleaning ovens, plastics, solar panels, mobile phones, and particle accelerators.

Isotopes of roentgenium

Roentgenium (111Rg) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 272Rg in 1994, which is also the only directly synthesized isotope; all others are decay products of nihonium, moscovium, and tennessine, and possibly copernicium, flerovium, and livermorium. There are 7 known radioisotopes from 272Rg to 282Rg. The longest-lived isotope is 282Rg with a half-life of 2.1 minutes, although the unconfirmed 283Rg and 286Rg may have a longer half-life of about 5.1 minutes and 10.7 minutes respectively.

Isotopes of tennessine

Tennessine (117Ts) is the most-recently synthesized synthetic element, and much of the data is hypothetical. As for any synthetic element, a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotopes to be synthesized were 293Ts and 294Ts in 2009. The longer-lived isotope is 294Ts with a half-life of 51 ms.

Julie Ezold

Julie Ezold (née Graudons) is a Nuclear Engineer at the Oak Ridge National Laboratory. She is campaign manager for the 252-Californium Campaign and was involved with the discovery of Tennessine.

Major actinide

Major actinides is a term used in the nuclear power industry that refers to the plutonium and uranium present in used nuclear fuel, as opposed to the minor actinides neptunium, americium, curium, berkelium, and californium.

Minor actinide

The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium (element 93), americium (element 95), curium (element 96), berkelium (element 97), californium (element 98), einsteinium (element 99), and fermium (element 100). The most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.

Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity and heat generation of used nuclear fuel in the medium term (300 to 20,000 years in the future).The plutonium from a power reactor tends to have a greater amount of Pu-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much Pu-241 the presence of americium-241 makes the plutonium less suitable for making a nuclear weapon. The ingrowth of americium in plutonium is one of the methods for identifying the origin of an unknown sample of plutonium and the time since it was last separated chemically from the americium.

Americium is commonly used in industry as both an alpha particle and as a low photon energy gamma radiation source. For instance it is used in many smoke detectors. Americium can be formed by neutron capture of Pu-239 and Pu-240 forming Pu-241 which then beta decays to Am-241. In general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission. Hence if MOX is used in a thermal reactor such as a boiling water reactor (BWR) or pressurized water reactor (PWR) then more americium can be expected in the used fuel than that from a fast neutron reactor.Some of the minor actinides have been found in fallout from bomb tests. See Actinides in the environment for details.

Moscovium

Moscovium is a synthetic chemical element with symbol Mc and atomic number 115. It was first synthesized in 2003 by a joint team of Russian and American scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. In December 2015, it was recognized as one of four new elements by the Joint Working Party of international scientific bodies IUPAC and IUPAP. On 28 November 2016, it was officially named after the Moscow Oblast, in which the JINR is situated.Moscovium is an extremely radioactive element: its most stable known isotope, moscovium-290, has a half-life of only 0.65 seconds. In the periodic table, it is a p-block transactinide element. It is a member of the 7th period and is placed in group 15 as the heaviest pnictogen, although it has not been confirmed to behave as a heavier homologue of the pnictogen bismuth. Moscovium is calculated to have some properties similar to its lighter homologues, nitrogen, phosphorus, arsenic, antimony, and bismuth, and to be a post-transition metal, although it should also show several major differences from them. In particular, moscovium should also have significant similarities to thallium, as both have one rather loosely bound electron outside a quasi-closed shell. About 100 atoms of moscovium have been observed to date, all of which have been shown to have mass numbers from 287 to 290.

Nihonium

Nihonium is a synthetic chemical element with the symbol Nh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactinide element in the p-block. It is a member of period 7 and group 13 (boron group).

Nihonium was first reported to have been created in 2003 by a Russian–American collaboration at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and in 2004 by a team of Japanese scientists at Riken in Wakō, Japan. The confirmation of their claims in the ensuing years involved independent teams of scientists working in the United States, Germany, Sweden, and China, as well as the original claimants in Russia and Japan. In 2015, the IUPAC/IUPAP Joint Working Party recognised the element and assigned the priority of the discovery and naming rights for the element to Riken, as it judged that they had demonstrated that they had observed element 113 before the JINR team did so. The Riken team suggested the name nihonium in 2016, which was approved in the same year. The name comes from the common Japanese name for Japan (日本, nihon).

Very little is known about nihonium, as it has only been made in very small amounts that decay away within seconds. The anomalously long lives of some superheavy nuclides, including some nihonium isotopes, are explained by the "island of stability" theory. Experiments support the theory, with the half-lives of the confirmed nihonium isotopes increasing from milliseconds to seconds as neutrons are added and the island is approached. Nihonium has been calculated to have similar properties to its homologues boron, aluminium, gallium, indium, and thallium. All but boron are post-transition metals, and nihonium is expected to be a post-transition metal as well. It should also show several major differences from them; for example, nihonium should be more stable in the +1 oxidation state than the +3 state, like thallium, but in the +1 state nihonium should behave more like silver and astatine than thallium. Preliminary experiments in 2017 showed that elemental nihonium is not very volatile; its chemistry remains largely unexplored.

Oganesson

Oganesson is a synthetic chemical element with symbol Og and atomic number 118. It was first synthesized in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, near Moscow in Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by the Joint Working Party of the international scientific bodies IUPAC and IUPAP. It was formally named on 28 November 2016. The name is in line with the tradition of honoring a scientist, in this case the nuclear physicist Yuri Oganessian, who has played a leading role in the discovery of the heaviest elements in the periodic table. It is one of only two elements named after a person who was alive at the time of naming, the other being seaborgium; it is also the only element whose namesake is alive today.Oganesson has the highest atomic number and highest atomic mass of all known elements. The radioactive oganesson atom is very unstable, and since 2005, only five (possibly six) atoms of the nuclide 294Og have been detected. Although this allowed very little experimental characterization of its properties and possible compounds, theoretical calculations have resulted in many predictions, including some surprising ones. For example, although oganesson is a member of group 18 – the first synthetic element to be so – it may be significantly reactive, unlike all the other elements of that group (the noble gases). It was formerly thought to be a gas under normal conditions but is now predicted to be a solid due to relativistic effects. On the periodic table of the elements it is a p-block element and the last one of the period 7.

Synthetic element

In chemistry, a synthetic element is a chemical element that does not occur naturally on Earth, and can only be created artificially. So far, 24 synthetic elements have been created (those with atomic numbers 95–118). All are unstable, decaying with half-lives ranging from 15.6 million years to a few hundred microseconds.

Seven other elements were first created artificially and thus considered synthetic, but later discovered to exist naturally (in trace quantities) as well; among them plutonium—first synthesized in 1940—the one best known to laypeople, because of its use in atomic bombs and nuclear reactors.

Transactinide element

In chemistry, transactinide elements (also transactinides, superheavy elements, or super-heavy elements) are the chemical elements with atomic numbers from 104 to 120. Their atomic numbers are immediately greater than those of the actinides, the heaviest of which is lawrencium (atomic number 103).

Glenn T. Seaborg first proposed the actinide concept, which led to the acceptance of the actinide series. He also proposed the transactinide series ranging from element 104 to 121 and the superactinide series approximately spanning elements 122 to 153. The transactinide seaborgium was named in his honor.By definition, transactinide elements are also transuranic elements, i.e. have an atomic number greater than uranium (92).

The transactinide elements all have electrons in the 6d subshell in their ground state. Except for rutherfordium and dubnium, even the longest-lasting isotopes of transactinide elements have extremely short half-lives of minutes or less. The element naming controversy involved the first five or six transactinide elements. These elements thus used systematic names for many years after their discovery had been confirmed. (Usually the systematic names are replaced with permanent names proposed by the discoverers relatively shortly after a discovery has been confirmed.)

Transactinides are radioactive and have only been obtained synthetically in laboratories. None of these elements have ever been collected in a macroscopic sample. Transactinide elements are all named after physicists and chemists or important locations involved in the synthesis of the elements.

IUPAC defines an element to exist if its lifetime is longer than 10−14 seconds, which is the time it takes for the nucleus to form an electron cloud.

Transuranium element

The transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92, which is the atomic number of uranium. All of these elements are unstable and decay radioactively into other elements.

Unbiquadium

Unbiquadium, also known as element 124 or eka-uranium, is the hypothetical chemical element with atomic number 124 and placeholder symbol Ubq. Unbiquadium and Ubq are the temporary IUPAC name and symbol, respectively, until the element is discovered, confirmed, and a permanent name is decided upon. In the periodic table, unbiquadium is expected to be a g-block superactinide and the sixth element in the 8th period. Unbiquadium has attracted attention, for it may lie within the island of stability, leading to longer half-lives, especially for 308Ubq which has a magic number of neutrons (184).

Despite several searches, unbiquadium has not been synthesized, nor have any naturally occurring isotopes been found to exist. It is hypothesized that the synthesis of unbiquadium will be far more challenging than that of lighter undiscovered elements, and nuclear instability may pose further difficulties in identifying unbiquadium, unless the island of stability has a stronger stabilizing effect than predicted in this region.

As a member of the superactinide series, unbiquadium is expected to bear some resemblance to its possible lighter congener uranium. The valence electrons of unbiquadium are expected to participate in chemical reactions fairly easily, though relativistic effects may significantly influence some of its properties; for example, the electron configuration has been calculated to differ considerably from the one predicted by the Aufbau principle.

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