Hassium is a synthetic chemical element with symbol Hs and atomic number 108. It is named after the German state of Hesse. It is a synthetic element and radioactive; the most stable known isotope, 270Hs, has a half-life of approximately 10 seconds.
In the periodic table of the elements, it is a d-block transactinide element. Hassium is a member of the 7th period and belongs to the group 8 elements: it is thus the sixth member of the 6d series of transition metals. Chemistry experiments have confirmed that hassium behaves as the heavier homologue to osmium in group 8. The chemical properties of hassium are characterized only partly, but they compare well with the chemistry of the other group 8 elements. In bulk quantities, hassium is expected to be a silvery metal that reacts readily with oxygen in the air, forming a volatile tetroxide.
|Pronunciation||/ˈhæsiəm/ (listen) |
|Mass number||270 (most stable isotope)|
|Hassium in the periodic table|
|Atomic number (Z)||108|
|Element category||transition metal|
|Electron configuration||[Rn] 5f14 6d6 7s2|
Electrons per shell
|2, 8, 18, 32, 32, 14, 2|
|Phase at STP||unknown phase (predicted)|
|Density (near r.t.)||41 g/cm3 (predicted)|
|Oxidation states||(+2), (+3), (+4), (+5), (+6), +8 (parenthesized: prediction)|
|Atomic radius||empirical: 126 pm (estimated)|
|Covalent radius||134 pm (estimated)|
|Crystal structure|| hexagonal close-packed (hcp)|
|Naming||after Hassia, Latin for Hesse, Germany, where it was discovered|
|Discovery||Gesellschaft für Schwerionenforschung (1984)|
|Main isotopes of hassium|
The synthesis of element 108 was first attempted in 1978 by a research team led by Yuri Oganessian at the Joint Institute for Nuclear Research (JINR) in Dubna, Moscow Oblast, Russian SFSR, Soviet Union. The team used a reaction that would generate 270108 from radium and calcium. The researchers were uncertain in interpreting result data; the paper did not unambiguously claim discovery. That same year, another team at JINR investigated the possibility of synthesis of element 108 in reactions between lead and iron; they were uncertain in interpreting result data as well, openly suggesting a possibility that element 108 had not been created.
New experiments were performed in 1983. In each experiment, a thin layer of a target material was installed on a rotating wheel and bombarded at a shallow angle. This was made so that fission fragments from spontaneously fissioning nuclides formed could escape the target and be detected in a number of fission track detectors surrounding the wheel. The experiments probably resulted in synthesis of element 108: bismuth was bombarded with manganese to obtain 263108, lead was bombarded with iron to obtain 264108, and californium was bombarded with neon to obtain 270108. These experiments were not claimed as a discovery and were only announced by Oganessian in a conference rather than in a written report.
In 1984, researchers in Dubna published a written report. The researchers performed a number of experiments set up as the previous ones with, bombarding target materials (bismuth and lead) with ions of lighter element (manganese and iron, correspondingly).
Also in 1984, a research team led by Peter Armbruster and Gottfried Münzenberg at the Gesellschaft für Schwerionenforschung (GSI; Institute for Heavy Ion Research) in Darmstadt, Hesse, West Germany, attempted to create element 108. The team bombarded a target of lead with accelerated nuclei of iron. They reported synthesis of 3 atoms of 265108.
In 1985, the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) formed a Joint Working Party (JWP) to assess discoveries and establish final names for the elements with atomic number greater than 100. The party held meetings with delegates from the three competing institutes; in 1990, they established criteria on recognition of an element, and in 1991, they finished the work on assessing discoveries, and disbanded. These results were published in 1993.
According to the report, the 1984 works from JINR and GSI simultaneously independently established synthesis of element 108. Of the two 1984 works, the one from GSI was said to be sufficient as a discovery on its own, while the JINR work, which preceded the GSI one, "very probably" displayed synthesis of element 108, but that is determined in retrospect given the work from Darmstadt. The report concluded that the major credit should be awarded to GSI.
According to Mendeleev's nomenclature for unnamed and undiscovered elements, hassium should be known as eka-osmium. In 1979, IUPAC published recommendations according to which the element was to be called unniloctium (with the corresponding symbol of Uno), a systematic element name as a placeholder, until the element was discovered (and the discovery then confirmed) and a permanent name was decided on. Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations were mostly ignored among scientists in the field, who either called it "element 108", with the symbol of E108, (108), or even simply 108, or used the proposed name "hassium".
The name hassium was proposed by Peter Armbruster and his colleagues, the officially recognised German discoverers, in September 1992. It is derived from the Latin name Hassia for the German state of Hesse where the institute is located. In 1994, IUPAC Commission on Nomenclature of Inorganic Chemistry recommended that element 108 be named hahnium (Hn) after the German physicist Otto Hahn so that elements named after Hahn and Lise Meitner (meitnerium) would be next to each other, honoring their joint discovery of nuclear fission. This was because they felt that Hesse did not merit an element being named after it. GSI protested saying that this contradicted the long-standing convention to give the discoverer the right to suggest a name; the American Chemical Society supported the GSI. IUPAC relented and the name hassium (Hs) was adopted internationally in 1997.
Hassium is not known to occur naturally on Earth; the half-lives of all its known isotopes are short enough that no primordial hassium would have survived to the present day. This does not rule out the possibility of unknown longer-lived isotopes or nuclear isomers existing, some of which could still exist in trace quantities today if they are long-lived enough. In the early 1960s, it was predicted that long-lived deformed isomers of hassium might occur naturally on Earth in trace quantities. This was theorized in order to explain the extreme radiation damage in some minerals that could not have been caused by any known natural radioisotopes, but could have been caused by superheavy elements.
In 1963, Soviet scientist Viktor Cherdyntsev, who had previously claimed the existence of primordial curium-247, claimed to have discovered element 108 (specifically, the 267Hs isotope, which supposedly had a half-life of 400 to 500 million years) in natural molybdenite and suggested the name sergenium (symbol Sg; at the time, this symbol had not yet been taken by seaborgium) for it; this name takes its origin in the name for the Silk Road and was explained as "coming from Kazakhstan". His rationale for claiming that sergenium was the heavier homologue to osmium was that minerals supposedly containing sergenium formed volatile oxides when boiled in nitric acid, similarly to osmium. His findings were criticized by Soviet physicist Vladimir Kulakov on the grounds that some of the properties Cherdyntsev claimed sergenium had were inconsistent with the then-current nuclear physics.
The chief questions raised by Kulakov were that the claimed alpha decay energy of sergenium was many orders of magnitude lower than expected and the half-life given was eight orders of magnitude shorter than what would be predicted for a nuclide alpha decaying with the claimed decay energy, but at the same time a corrected half-life in the region of 1016 years would be impossible as it would imply that the samples contained about 100 milligrams of sergenium. In 2003 it was suggested that the observed alpha decay with energy 4.5 MeV could be due to a low-energy and strongly enhanced transition between different hyperdeformed states of a hassium isotope around 271Hs, thus suggesting that the existence of superheavy elements in nature was at least possible, although unlikely.
In 2004, the Joint Institute for Nuclear Research conducted a search for natural hassium. This was done underground to avoid interference and false positives from cosmic rays, but no results have been released, strongly implying that no natural hassium was found. The possible extent of primordial hassium on Earth is uncertain; it might now only exist in traces, or could even have completely decayed by now after having caused the radiation damage long ago.
In 2006, it was hypothesized that an isomer of 271Hs might have a half-life of around (2.5±0.5)×108 years, which would explain the observation of alpha particles with energies of around 4.4 MeV in some samples of molybdenite and osmiridium. This isomer of 271Hs could be produced from the beta decay of 271Bh and 271Sg, which, being homologous to rhenium and molybdenum respectively, should occur in molybdenite along with rhenium and molybdenum if they occurred in nature. Since hassium is homologous to osmium, it should also occur along with osmium in osmiridium if it occurred in nature. The decay chains of 271Bh and 271Sg are very hypothetical and the predicted half-life of this hypothetical hassium isomer is not long enough for any sufficient quantity to remain on Earth. It is possible that more 271Hs may be deposited on the Earth as the Solar System travels through the spiral arms of the Milky Way, which would also explain excesses of plutonium-239 found on the floors of the Pacific Ocean and the Gulf of Finland, but minerals enriched with 271Hs are predicted to also have excesses of uranium-235 and lead-207, and would have different proportions of elements that are formed during spontaneous fission, such as krypton, zirconium, and xenon. Thus, the occurrence of hassium in nature in minerals such as molybdenite and osmiride is theoretically possible, but highly unlikely.
A 2007 calculation on the decay properties of unknown neutron-rich isotopes of superheavy elements suggested that the isotope 292Hs may be the most stable superheavy nucleus against alpha decay and spontaneous fission, as a consequence of the shell closure at N = 184. As such, it was considered as a candidate to exist in nature. However, this nucleus is predicted to be highly unstable toward beta decay, and any beta-stable isotopes of hassium (such as 286Hs) would be too unstable in the other decay channels to possibly be observed in nature. Indeed, a subsequent search for 292Hs in nature along with its congener osmium was unsuccessful, setting an upper limit to its abundance at 3×10-15 grams of hassium per gram of osmium.
|263Hs||0.76 ms||α, SF||2008||208Pb(56Fe,n)|
|264Hs||0.54 ms||α, SF||1986||207Pb(58Fe,n)|
|265Hs||1.96 ms||α, SF||1984||208Pb(58Fe,n)|
|266Hs||3.02 ms||α, SF||2000||270Ds(—,α)|
|267Hs||55 ms||α, SF||1995||238U(34S,5n)|
Hassium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Twelve different isotopes have been reported with atomic masses from 263 to 277 (with the exceptions of 272, 274, and 276), three of which, hassium-265, hassium-267, hassium-269, have known metastable states. Most of these decay predominantly through alpha decay, but some also undergo spontaneous fission.
The lightest isotopes, which usually have shorter half-lives were synthesized by direct fusion between two lighter nuclei and as decay products. The heaviest isotope produced by direct fusion is 271Hs; heavier isotopes have only been observed as decay products of elements with larger atomic numbers. In 1999, scientists at University of California in Berkeley, California, United States, announced that they had succeeded in synthesizing three atoms of 293Og. These parent nuclei were reported to have successively emitted three alpha particles to form hassium-273 nuclei, which were claimed to have undergone an alpha decay, emitting alpha particles with decay energies of 9.78 and 9.47 MeV and half-life 1.2 s, but their claim was retracted in 2001 as it came out the data was fabricated. The isotope was successfully produced in 2010 by the same team. The new data matched the previous (fabricated) data.
According to calculations, 108 is a proton magic number for deformed nuclei (nuclei that are far from spherical), and 162 is a neutron magic number for deformed nuclei. This means that such nuclei are permanently deformed in their ground state but have high, narrow fission barriers to further deformation and hence relatively long life-times to spontaneous fission. The spontaneous fission half-lives in this region are typically reduced by a factor of 109 in comparison with those in the vicinity of the spherical doubly magic nucleus 298Fl, caused by the narrower fission barrier for such deformed nuclei. Hence, the nucleus 270Hs has promise as a deformed doubly magic nucleus. Experimental data from the decay of the darmstadtium (Z=110) isotopes 271Ds and 273Ds provides strong evidence for the magic nature of the N=162 sub-shell. The syntheses of 269Hs, 270Hs, and 271Hs also fully support the assignment of N=162 as a magic number. In particular, the low decay energy for 270Hs is in complete agreement with calculations.
Evidence for the magicity of the Z=108 proton shell can be obtained from two sources: the variation in the partial spontaneous fission half-lives for isotones and the large gap in the alpha Q value for isotonic nuclei of hassium and darmstadtium. For spontaneous fission, it is necessary to measure the half-lives for the isotonic nuclei 268Sg, 270Hs and 272Ds. Since the isotopes 268Sg and 272Ds are not currently known, and fission of 270Hs has not been measured, this method cannot yet be used to confirm the stabilizing nature of the Z=108 shell. Good evidence for the magicity of the Z=108 shell can nevertheless be found from the large differences in the alpha decay energies measured for 270Hs, 271Ds and 273Ds. More conclusive evidence would come from the determination of the decay energy for the unknown nucleus 272Ds.
Various calculations show that hassium should be the heaviest known group 8 element, consistent with the periodic law. Its properties should generally match those expected for a heavier homologue of osmium, with a few deviations arising from relativistic effects.
The previous members of group 8 have relatively high melting points (Fe, 1538 °C; Ru, 2334 °C; Os, 3033 °C). Much like them, hassium is predicted to be a solid at room temperature, although the melting point of hassium has not been precisely calculated. Hassium should crystallize in the hexagonal close-packed structure (c/a = 1.59), similarly to its lighter congener osmium. Pure metallic hassium is calculated to have a bulk modulus (resistance to uniform compression) comparable to that of diamond (442 GPa). Hassium is expected to have a bulk density of 40.7 g/cm3, the highest of any of the 118 known elements and nearly twice the density of osmium, the most dense measured element, at 22.61 g/cm3. This results from hassium's high atomic weight, the lanthanide and actinide contractions, and relativistic effects, although production of enough hassium to measure this quantity would be impractical, and the sample would quickly decay. Osmium is the densest element of the first 6 periods, and its heavier congener hassium is expected to be the densest element of the first 7 periods.
The atomic radius of hassium is expected to be around 126 pm. Due to the relativistic stabilization of the 7s orbital and destabilization of the 6d orbital, the Hs+ ion is predicted to have an electron configuration of [Rn] 5f14 6d5 7s2, giving up a 6d electron instead of a 7s electron, which is the opposite of the behavior of its lighter homologues. On the other hand, the Hs2+ ion is expected to have an electron configuration of [Rn] 5f14 6d5 7s1, analogous to that calculated for the Os2+ ion.
|Element||Stable oxidation states|
Hassium is the sixth member of the 6d series of transition metals and is expected to be much like the platinum group metals. Calculations on its ionization potentials, atomic radius, as well as radii, orbital energies, and ground levels of its ionized states are similar to that of osmium, implying that hassium's properties would resemble those of the other group 8 elements, iron, ruthenium, and osmium. Some of these properties were confirmed by gas-phase chemistry experiments. The group 8 elements portray a wide variety of oxidation states, but ruthenium and osmium readily portray their group oxidation state of +8 (the second-highest known oxidation state for any element, which is very rare for other elements) and this state becomes more stable as the group is descended. Thus hassium is expected to form a stable +8 state. Analogously to its lighter congeners, hassium is expected to also show other stable lower oxidation states, such as +6, +5, +4, +3, and +2. Indeed, hassium(IV) is expected to be more stable than hassium(VIII) in aqueous solution.
The group 8 elements show a very distinctive oxide chemistry which allows extrapolations to be made easily for hassium. All the lighter members have known or hypothetical tetroxides, MO4. Their oxidising power decreases as one descends the group. FeO4 is not known due to its extraordinarily large electron affinity (the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion) which results in the formation of the well-known oxoanion ferrate(VI), FeO2−
4. Ruthenium tetroxide, RuO4, formed by oxidation of ruthenium(VI) in acid, readily undergoes reduction to ruthenate(VI), RuO2−
4. Oxidation of ruthenium metal in air forms the dioxide, RuO2. In contrast, osmium burns to form the stable tetroxide, OsO4, which complexes with the hydroxide ion to form an osmium(VIII) -ate complex, [OsO4(OH)2]2−. Therefore, eka-osmium properties for hassium should be demonstrated by the formation of a stable, very volatile tetroxide HsO4, which undergoes complexation with hydroxide to form a hassate(VIII), [HsO4(OH)2]2−. Ruthenium tetroxide and osmium tetroxide are both volatile, due to their symmetrical tetrahedral molecular geometry and their being charge-neutral; hassium tetroxide should similarly be a very volatile solid. The trend of the volatilities of the group 8 tetroxides is known to be RuO4 < OsO4 > HsO4, which completely confirms the calculated results. In particular, the calculated enthalpies of adsorption (the energy required for the adhesion of atoms, molecules, or ions from a gas, liquid, or dissolved solid to a surface) of HsO4, −(45.4 ± 1) kJ/mol on quartz, agrees very well with the experimental value of −46±2 kJ/mol.
Despite the fact that the selection of a volatile hassium compound (hassium tetroxide) for gas-phase chemical studies was clear from the beginning, the chemical characterization of hassium was considered a difficult task for a long time. Although hassium isotopes were first synthesized in 1984, it was not until 1996 that a hassium isotope long-lived enough to allow chemical studies to be performed was synthesized. Unfortunately, this hassium isotope, 269Hs, was then synthesized indirectly from the decay of 277Cn; not only are indirect synthesis methods not favourable for chemical studies, but also the reaction that produced the isotope 277Cn had a low yield (its cross-section was only 1 pb), and thus did not provide enough hassium atoms for a chemical investigation. The direct synthesis of 269Hs and 270Hs in the reaction 248Cm(26Mg,xn)274−xHs (x = 4 or 5) appeared more promising, as the cross-section for this reaction was somewhat larger, at 7 pb. This yield was still around ten times lower than that for the reaction used for the chemical characterization of bohrium. New techniques for irradiation, separation, and detection had to be introduced before hassium could be successfully characterized chemically as a typical member of group 8 in early 2001.
Ruthenium and osmium have very similar chemistry due to the lanthanide contraction, but iron shows some differences from them: for example, although ruthenium and osmium form stable tetroxides in which the metal is in the +8 oxidation state, iron does not. Consequently, in preparation for the chemical characterization of hassium, researches focused on ruthenium and osmium rather than iron, as hassium was expected to also be similar to ruthenium and osmium due to the actinide contraction. Nevertheless, in the planned experiment to study hassocene (Hs(C5H5)2), ferrocene may also be used for comparison along with ruthenocene and osmocene.
The first chemistry experiments were performed using gas thermochromatography in 2001, using 172Os and 173Os as a reference. During the experiment, 5 hassium atoms were synthesized using the reaction 248Cm(26Mg,5n)269Hs. They were then thermalized and oxidized in a mixture of helium and oxygen gas to form the tetroxide.
The measured deposition temperature indicated that hassium(VIII) oxide is less volatile than osmium tetroxide, OsO4, and places hassium firmly in group 8. However, the enthalpy of adsorption for HsO4 measured, −46±2 kJ/mol, was significantly lower than what was predicted, −36.7±1.5 kJ/mol, indicating that OsO4 was more volatile than HsO4, contradicting earlier calculations, which implied that they should have very similar volatilities. For comparison, the value for OsO4 is −39±1 kJ/mol. It is possible that hassium tetroxide interacts differently with the different chemicals (silicon nitride and silicon dioxide) used for the detector; further research is required, including more accurate measurements of the nuclear properties of 269Hs and comparisons with RuO4 in addition to OsO4.
In 2004 scientists reacted hassium tetroxide and sodium hydroxide to form sodium hassate(VIII), a reaction well known with osmium. This was the first acid-base reaction with a hassium compound, forming sodium hassate(VIII):
The team from the University of Mainz were planning to study the electrodeposition of hassium atoms using the new TASCA facility at the GSI. Their aim was to use the reaction 226Ra(48Ca,4n)270Hs. In addition, scientists at the GSI were hoping to utilize TASCA to study the synthesis and properties of the hassium(II) compound hassocene, Hs(C5H5)2, using the reaction 226Ra(48Ca,xn). This compound is analogous to the lighter ferrocene, ruthenocene, and osmocene, and is expected to have the two cyclopentadienyl rings in an eclipsed conformation like ruthenocene and osmocene and not in a staggered conformation like ferrocene. Hassocene was chosen because it has hassium in the low formal oxidation state of +2 (although the bonding between the metal and the rings is mostly covalent in metallocenes) rather than the high +8 state which had previously been investigated, and relativistic effects were expected to be stronger in the lower oxidation state. Many metals in the periodic table form metallocenes, so that trends could be more easily determined, and the highly symmetric structure of hassocene and its low number of atoms also make relativistic calculations easier. Hassocene should be a stable and highly volatile compound.
Bohrium is a synthetic chemical element with symbol Bh and atomic number 107. It is named after Danish physicist Niels Bohr. As a synthetic element, it can be created in a laboratory but is not found in nature. It is radioactive: its most stable known isotope, 270Bh, has a half-life of approximately 61 seconds, though the unconfirmed 278Bh may have a longer half-life of about 690 seconds.
In the periodic table of the elements, it is a d-block transactinide element. It is a member of the 7th period and belongs to the group 7 elements as the fifth member of the 6d series of transition metals. Chemistry experiments have confirmed that bohrium behaves as the heavier homologue to rhenium in group 7. The chemical properties of bohrium are characterized only partly, but they compare well with the chemistry of the other group 7 elements.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.Electron configurations of the elements (data page)
This page shows the electron configurations of the neutral gaseous atoms in their ground states. For each atom the subshells are given first in concise form, then with all subshells written out, followed by the number of electrons per shell. Electron configurations of elements beyond hassium (element 108) are predicted.
As an approximate rule, electron configurations are given by the Aufbau principle and the Madelung rule. However there are numerous exceptions; for example the lightest exception is chromium, which would be predicted to have the configuration 1s2 2s2 2p6 3s2 3p6 3d4 4s2, written as [Ar] 3d4 4s2, but whose actual configuration given in the table below is [Ar] 3d5 4s1.Extended periodic table
An extended periodic table theorizes about chemical elements beyond those currently known in the periodic table and proven up through oganesson, which completes the seventh period (row) in the periodic table at atomic number (Z) 118.
If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out (as with the existing periods) to illustrate periodically recurring trends in the properties of the elements concerned. Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to have an additional so-called g-block, containing at least 18 elements with partially filled g-orbitals in each period.An eight-period table containing this block was suggested by Glenn T. Seaborg in 1969. The first element of the g-block may have atomic number 121, and thus would have the systematic name unbiunium. Despite many searches, no elements in this region have been synthesized or discovered in nature.According to the orbital approximation in quantum mechanical descriptions of atomic structure, the g-block would correspond to elements with partially filled g-orbitals, but spin-orbit coupling effects reduce the validity of the orbital approximation substantially for elements of high atomic number. While Seaborg's version of the extended period had the heavier elements following the pattern set by lighter elements, as it did not take into account relativistic effects, models that take relativistic effects into account do not. Pekka Pyykkö and Burkhard Fricke used computer modeling to calculate the positions of elements up to Z = 172, and found that several were displaced from the Madelung rule. As a result of uncertainty and variability in predictions of chemical and physical properties of elements beyond 120, there is currently no consensus on their placement in the extended periodic table.
Elements in this region are likely to be highly unstable with respect to radioactive decay and undergo alpha decay or spontaneous fission with extremely short half-lives, though element 126 is hypothesized to be within an island of stability that is resistant to fission but not to alpha decay. Other islands of stability beyond the known elements may also be possible, including one theorized around element 164, though the extent of stabilizing effects from closed nuclear shells is uncertain. It is not clear how many elements beyond the expected island of stability are physically possible, whether period 8 is complete, or if there is a period 9. The International Union of Pure and Applied Chemistry (IUPAC) defines an element to exist if its lifetime is longer than 10−14 seconds (0.01 picoseconds, or 10 femtoseconds), which is the time it takes for the nucleus to form an electron cloud.As early as 1940, it was noted that a simplistic interpretation of the relativistic Dirac equation runs into problems with electron orbitals at Z > 1/α ≈ 137, suggesting that neutral atoms cannot exist beyond element 137, and that a periodic table of elements based on electron orbitals therefore breaks down at this point. On the other hand, a more rigorous analysis calculates the analogous limit to be Z ≈ 173 where the 1s subshell dives into the Dirac sea, and that it is instead not neutral atoms that cannot exist beyond element 173, but bare nuclei, thus posing no obstacle to the further extension of the periodic system. Atoms beyond this critical atomic number are called supercritical atoms.Gottfried Münzenberg
Gottfried Münzenberg (born 17 March 1940 in Nordhausen, Province of Saxony) is a German physicist.
He studied physics at Justus-Liebig-Universität in Giessen and Leopold-Franzens-Universität Innsbruck and completed his studies with a Ph.D. at the University of Giessen, Germany, in 1971. In 1976 he moved to the department of nuclear chemistry at GSI in Darmstadt, Germany, which was headed by Peter Armbruster. He played a leading role in the construction of SHIP, the 'Separator of Heavy Ion Reaction Products'. He was the driving force in the discovery of the cold heavy ion fusion and the discovery of the elements bohrium (Bh Z=107), hassium (Hs Z=108), meitnerium (Mt Z=109), darmstadtium (Ds Z=110), roentgenium (Rg Z=111) and copernicium (Cn Z=112). In 1984 he became head of the new GSI project, the fragment separator, a project which opened new research topics, such as interactions of relativistic heavy ions with matter, production and separation of exotic nuclear beams and structure of exotic nuclei. He directed the Nuclear Structure and Nuclear Chemistry department of the GSI and was professor of physics at the University of Mainz until he retired in March 2005.
Gottfried Münzenberg was born into a family of Protestant ministers (father Pastor Heinz and mother Helene Münzenberg). All his life he is deeply concerned about the philosophical and theological implications of physics.
Among the rewards he received should be mentioned the Röntgen-Prize of the University of Giessen in 1983 and (together with Sigurd Hofmann) the Otto-Hahn-Prize of the city of Frankfurt/Main in 1996.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.Inorganic compounds by element
This is a list of common inorganic and organometallic compounds of each element. Compounds are listed alphabetically by their chemical element name rather than by symbol, as in list of inorganic compounds.Isotopes of hassium
Hassium (108Hs) 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 265Hs in 1984. There are 12 known isotopes from 263Hs to 277Hs and 1–4 isomers. The longest-lived isotope is 270Hs with a half-life of 10 seconds.List of chemical elements naming controversies
The currently accepted names and symbols of the chemical elements are determined by the International Union of Pure and Applied Chemistry (IUPAC), usually following recommendations by the recognized discoverers of each element. However the names of several elements have been the subject of controversies until IUPAC established an official name. In most cases the controversy was due to a priority dispute as to who first found conclusive evidence for the existence of an element, or as to what evidence was in fact conclusive.List of radioactive isotopes by half-life
This is a list of radioactive isotopes ordered by half-life from shortest to longest.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.Meitnerium
Meitnerium is a synthetic chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds, although the unconfirmed meitnerium-282 may have a longer half-life of 67 seconds. The GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, first created this element in 1982. It is named after Lise Meitner.
In the periodic table, meitnerium is a d-block transactinide element. It is a member of the 7th period and is placed in the group 9 elements, although no chemical experiments have yet been carried out to confirm that it behaves as the heavier homologue to iridium in group 9 as the seventh member of the 6d series of transition metals. Meitnerium is calculated to have similar properties to its lighter homologues, cobalt, rhodium, and iridium.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.Peter Armbruster
Peter Armbruster (born 25 July 1931 in Dachau, Bavaria) is a physicist at the Gesellschaft für Schwerionenforschung (GSI) facility in Darmstadt, Germany, and is credited with co-discovering elements 107 (bohrium), 108 (hassium), 109 (meitnerium), 110 (darmstadtium), 111 (roentgenium), and 112 (copernicium) with research partner Gottfried Münzenberg.
He studied physics at the Technical University of Stuttgart and Munich, and obtained his Ph.D. in 1961 under Heinz Maier-Leibnitz, Technical University of Munich. His major research fields are fission, interaction of heavy ions in matter and atomic physics with fission product beams at the Research Centre of Jülich (1965 to 1970). He was Senior Scientist at the Gesellschaft für Schwerionenforschung Darmstadt, GSI, from 1971 to 1996. From 1989 to 1992 he was research Director of the European Institut Laue-Langevin (ILL), Grenoble. Since 1996 he has been involved in a project on incineration of nuclear waste by spallation and fission reactions.
He was affiliated as professor to the University of Cologne (1968) and the Darmstadt University of Technology since 1984.
He has received many awards for his work, including the Max-Born Medal awarded by the Institute of Physics London and the Deutsche Physikalische Gesellschaft in 1988, and the Stern-Gerlach Medal awarded by the Deutsche Physikalische Gesellschaft in 1997. The American Chemical Society honoured Peter Armbruster 1997 as one of few non-Americans with the 'Nuclear Chemistry Award'.Seaborgium
Seaborgium is a synthetic chemical element with symbol Sg and atomic number 106. It is named after the American nuclear chemist Glenn T. Seaborg. As a synthetic element, it can be created in a laboratory but is not found in nature. It is also radioactive; the most stable known isotope, 269Sg, has a half-life of approximately 14 minutes.In the periodic table of the elements, it is a d-block transactinide element. It is a member of the 7th period and belongs to the group 6 elements as the fourth member of the 6d series of transition metals. Chemistry experiments have confirmed that seaborgium behaves as the heavier homologue to tungsten in group 6. The chemical properties of seaborgium are characterized only partly, but they compare well with the chemistry of the other group 6 elements.
In 1974, a few atoms of seaborgium were produced in laboratories in the Soviet Union and in the United States. The priority of the discovery and therefore the naming of the element was disputed between Soviet and American scientists, and it was not until 1997 that International Union of Pure and Applied Chemistry (IUPAC) established seaborgium as the official name for the element. It is one of only two elements named after a living person at the time of naming, the other being oganesson, element 118.Symbol (chemistry)
In relation to the chemical elements, a symbol is a code for a chemical element. Many functional groups have their own chemical symbol, e.g. Ph for the phenyl group, and Me for the methyl group. Chemical symbols for elements normally consist of one or two letters from the Latin alphabet, but can contain three when the element has a systematic temporary name (as of March 2017, no discovered elements have such a name), and are written with the first letter capitalized.
Earlier chemical element symbols stem from classical Latin and Greek vocabulary. For some elements, this is because the material was known in ancient times, while for others, the name is a more recent invention. For example, "He" is the symbol for helium (New Latin name, not known in ancient Roman times), "Pb" for lead (plumbum in Latin), and "Hg" for mercury (hydrargyrum in Greek). Some symbols come from other sources, like "W" for tungsten (Wolfram in German, not known in Roman times).
Temporary symbols assigned to newly or not-yet synthesized elements use 3-letter symbols based on their atomic numbers. For example, "Uno" was the temporary symbol for hassium (element 108) which had the temporary name of unniloctium.
Chemical symbols may be modified by the use of prepended superscripts or subscripts to specify a particular isotope of an atom. Additionally, appended superscripts may be used to indicate the ionization or oxidation state of an element. They are widely used in chemistry and they have been officially chosen by the International Union of Pure and Applied Chemistry (IUPAC). There are also some historical symbols that are no longer officially used.
Attached subscripts or superscripts specifying a nuclide or molecule have the following meanings and positions:
The nucleon number (mass number) is shown in the left superscript position (e.g., 14N). This number defines the specific isotope. Various letters, such as "m" and "f" may also be used here to indicate a nuclear isomer (e.g., 99mTc). Alternately, the number here can represent a specific spin state (e.g., 1O2). These details can be omitted if not relevant in a certain context.
The proton number (atomic number) may be indicated in the left subscript position (e.g., 64Gd). The atomic number is redundant to the chemical element, but is sometimes used to emphasize the change of numbers of nucleons in a nuclear reaction.
If necessary, a state of ionization or an excited state may be indicated in the right superscript position (e.g., state of ionization Ca2+).
The number of atoms of an element in a molecule or chemical compound is shown in the right subscript position (e.g., N2 or Fe2O3). If this number is one, it is normally omitted - the number one is then implicit.
A radical is indicated by a dot on the right side (e.g., Cl• for a neutral chlorine atom). This is often omitted unless relevant to a certain context because it is already deducible from the charge and atomic number information values.In Chinese, each chemical element has a dedicated character, usually created for the purpose (see Chemical elements in East Asian languages). However, Latin symbols are also used, especially in formulas.
A list of current, dated, as well as proposed and historical signs and symbols is included here with its signification. Also given is each element's atomic number, atomic weight or the atomic mass of the most stable isotope, group and period numbers on the periodic table, and etymology of the symbol.
Hazard pictographs are another type of symbols used in chemistry.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.Transfermium Wars
The names for the chemical elements 104 to 106 were the subject of a major controversy starting in the 1960s, described by some nuclear chemists as the Transfermium Wars because it concerned the elements following fermium (element 100) on the periodic table.
This controversy arose from disputes between American scientists and Soviet scientists as to which had first isolated these elements. The final resolution of this controversy in 1997 also decided the names of elements 107 to 109.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.