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.[1][2]

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.[3]

List of the known transactinide elements

Super heavy elements (polyatomic)

Work performed from 1964 to 2013 at four laboratories – the Lawrence Berkeley National Laboratory in the USA, the Joint Institute for Nuclear Research in the USSR (later Russia), the GSI Helmholtz Centre for Heavy Ion Research in Germany, and RIKEN in Japan – identified and confirmed the elements from rutherfordium to oganesson according to the criteria of the IUPACIUPAP Transfermium Working Group and subsequent Joint Working Parties. These discoveries complete the seventh row of the periodic table.

The remaining two transactinides, ununennium (element 119) and unbinilium (element 120), have not yet been synthesized. They would begin an eighth period.

Characteristics

Due to their short half-lives (for example, the most stable isotope of seaborgium has a half-life of 3.1 minutes, and half-lives decrease gradually going to the right of the group) and the low yield of the nuclear reactions that produce them, new methods have had to be created to determine their gas-phase and solution chemistry based on very small samples of a few atoms each. Relativistic effects become very important in this region of the periodic table, causing the filled 7s orbitals, empty 7p orbitals, and filling 6d orbitals to all contract inwards toward the atomic nucleus. This causes a relativistic stabilization of the 7s electrons and makes the 7p orbitals accessible in low excitation states.[2]

Elements 104 to 112, rutherfordium through copernicium, form the 6d series of transition elements: for elements 104–108 and 112, experimental evidence shows them to behave as expected for their position in the periodic table. They are expected to have ionic radii between those of their 5d transition metal homologs and their actinide pseudohomologs: for example, Rf4+ is calculated to have ionic radius 76 pm, between the values for Hf4+ (71 pm) and Th4+ (94 pm). Their ions should also be less polarizable than those of their 5d homologs. Relativistic effects are expected to reach a maximum at the end of this series, at roentgenium (element 111) and copernicium (element 112). Nevertheless, many important properties of the transactinides are still not yet known experimentally, though theoretical calculations have been performed.[2]

Elements 113 to 118, nihonium through oganesson, should form a 7p series, completing the seventh period in the periodic table. Their chemistry will be greatly influenced by the very strong relativistic stabilization of the 7s electrons and a strong spin-orbit coupling effect "tearing" the 7p subshell apart into two sections, one more stabilized (7p1/2, holding two electrons) and one more destabilized (7p3/2, holding four electrons). Additionally, the 6d electrons are still destabilized in this region and hence may be able to contribute some transition metal character to the first few 7p elements. Lower oxidation states should be stabilized here, continuing group trends, as both the 7s and 7p1/2 electrons exhibit the inert pair effect. These elements are expected to largely continue to follow group trends, though with relativistic effects playing an increasingly larger role. In particular, the large 7p splitting results in an effective shell closure at flerovium (element 114) and a hence much higher than expected chemical activity for oganesson (element 118).[2]

Element 118 is the last element that has been claimed to have been synthesized. The next two elements, elements 119 and 120, should form an 8s series and be an alkali and alkaline earth metal respectively. The 8s electrons are expected to be relativistically stabilized, so that the trend towards higher reactivity down these groups will reverse direction and the elements will behave more like their period 5 homologs, rubidium and strontium. Nevertheless, the 7p3/2 orbital is still relativistically destabilized, potentially giving these elements larger ionic radii and perhaps even being able to participate chemically. In this region, the 8p electrons are also relativistically stabilized, resulting in a ground-state 8s28p1 valence electron configuration for element 121. Large changes are expected to occur in the subshell structure in going from element 120 to element 121: for example, the radius of the 5g orbitals should drop drastically, from 25 Bohr units in element 120 in the excited [Og]5g18s1 configuration to 0.8 Bohr units in element 121 in the excited [Og]5g17d18s1 configuration, in a phenomenon called "radial collapse" that occurs at element 125. Element 122 should add a further 7d electron to element 121's electron configuration. Elements 121 and 122 should be homologs of actinium and thorium, respectively.[2]

Beyond element 121, the superactinide series is expected to begin, when the 8s electrons and the filling 8p1/2, 7d3/2, 6f5/2, and 5g7/2 subshells determine the chemistry of these elements. Complete and accurate calculations are not available for elements beyond 123[4] because of the extreme complexity of the situation: the 5g, 6f, and 7d orbitals should have about the same energy level, and in the region of element 160 the 9s, 8p3/2, and 9p1/2 orbitals should also be about equal in energy. This will cause the electron shells to mix so that the block concept no longer applies very well, and will also result in novel chemical properties that will make positioning these elements in a periodic table very difficult. For example, element 164 is expected to mix characteristics of the elements of group 10, 12, and 18.[2]

See also

References

  1. ^ IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the "Red Book" IR 3-6) Archived October 27, 2006, at the Wayback Machine
  2. ^ a b c d e f Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, eds. (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer. ISBN 978-1-4020-3555-5.
  3. ^ Kernchemie
  4. ^ van der Schoor, K. (2016). Electronic structure of element 123 (PDF) (Thesis). Rijksuniversiteit Groningen.
Bohrium

Bohrium is a synthetic chemical element with the 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.

Copernicium

Copernicium is a synthetic chemical element with the symbol Cn and atomic number 112. Its known isotopes are extremely radioactive, and have only been created in a laboratory. The most stable known isotope, copernicium-285, has a half-life of approximately 29 seconds. Copernicium was first created in 1996 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the astronomer Nicolaus Copernicus.

In the periodic table of the elements, copernicium is a d-block transactinide element and a group 12 element. During reactions with gold, it has been shown to be an extremely volatile metal, so much so that it is probably a gas at standard temperature and pressure.

Copernicium is calculated to have several properties that differ from its lighter homologues in group 12, zinc, cadmium and mercury; due to relativistic effects, it may even give up its 6d electrons instead of its 7s ones. Copernicium has also been calculated to possibly show the oxidation state +4, while mercury shows it in only one compound of disputed existence and zinc and cadmium do not show it at all. It has also been predicted to be more difficult to oxidize copernicium from its neutral state than the other group 12 elements.

Darmstadtium

Darmstadtium is a synthetic chemical element with the symbol Ds and atomic number 110. It is an extremely radioactive synthetic element. The most stable known isotope, darmstadtium-281, has a half-life of approximately 12.7 seconds. Darmstadtium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near the city of Darmstadt, Germany, after which it was named.

In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and is placed in the group 10 elements, although no chemical experiments have yet been carried out to confirm that it behaves as the heavier homologue to platinum in group 10 as the eighth member of the 6d series of transition metals. Darmstadtium is calculated to have similar properties to its lighter homologues, nickel, palladium, and platinum.

Flerovium

Flerovium is a superheavy artificial chemical element with the symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. The element is named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna, Russia, where the element was discovered in 1998. The name of the laboratory, in turn, honours the Russian physicist Georgy Flyorov (Флёров in Cyrillic, hence the transliteration of "yo" to "e"). The name was adopted by IUPAC on 30 May 2012.

In the periodic table of the elements, it is a transactinide element in the p-block. It is a member of the 7th period and is the heaviest known member of the carbon group; it is also the heaviest element whose chemistry has been investigated. Initial chemical studies performed in 2007–2008 indicated that flerovium was unexpectedly volatile for a group 14 element; in preliminary results it even seemed to exhibit properties similar to those of the noble gases. More recent results show that flerovium's reaction with gold is similar to that of copernicium, showing that it is a very volatile element that may even be gaseous at standard temperature and pressure, that it would show metallic properties, consistent with it being the heavier homologue of lead, and that it would be the least reactive metal in group 14. The question of whether flerovium behaves more like a metal or a noble gas is still unresolved as of 2018.

About 90 atoms of flerovium have been observed: 58 were synthesized directly, and the rest were made from the radioactive decay of heavier elements. All of these flerovium atoms have been shown to have mass numbers from 284 to 290. The most stable known flerovium isotope, flerovium-289, has a half-life of around 1.9 seconds, but it is possible that the unconfirmed flerovium-290 with one extra neutron may have a longer half-life of 19 seconds; this would be one of the longest half-lives of any isotope of any element at these farthest reaches of the periodic table. Flerovium is predicted to be near the centre of the theorized island of stability, and it is expected that heavier flerovium isotopes, especially the possibly doubly magic flerovium-298, may have even longer half-lives.

Hassium

Hassium is a synthetic chemical element with the 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, 269Hs, has a half-life of approximately 16 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.

Livermorium

Livermorium is a synthetic chemical element with the symbol Lv and has an atomic number of 116. It is an extremely radioactive element that has only been created in the laboratory and has not been observed in nature. The element is named after the Lawrence Livermore National Laboratory in the United States, which collaborated with the Joint Institute for Nuclear Research (JINR) in Dubna, Russia to discover livermorium during experiments made between 2000 and 2006. The name of the laboratory refers to the city of Livermore, California where it is located, which in turn was named after the rancher and landowner Robert Livermore. The name was adopted by IUPAC on May 30, 2012. 4 isotopes of livermorium are known, with mass numbers between 290 and 293 inclusive; the longest-lived among them is livermorium-293 with a half-life of about 60 milliseconds. A fifth possible isotope with mass number 294 has been reported but not yet confirmed.

In the periodic table, it is a p-block transactinide element. It is a member of the 7th period and is placed in group 16 as the heaviest chalcogen, although it has not been confirmed to behave as the heavier homologue to the chalcogen polonium. Livermorium is calculated to have some similar properties to its lighter homologues (oxygen, sulfur, selenium, tellurium, and polonium), and be a post-transition metal, although it should also show several major differences from them.

Meitnerium

Meitnerium is a synthetic chemical element with the 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.

Mendelevium

Mendelevium is a synthetic element with the symbol Md (formerly Mv) and atomic number 101. A metallic radioactive transuranic element in the actinide series, it is the first element that currently cannot be produced in macroscopic quantities through neutron bombardment of lighter elements. It is the third-to-last actinide and the ninth transuranic element. It can only be produced in particle accelerators by bombarding lighter elements with charged particles. A total of sixteen mendelevium isotopes are known, the most stable being 258Md with a half-life of 51 days; nevertheless, the shorter-lived 256Md (half-life 1.17 hours) is most commonly used in chemistry because it can be produced on a larger scale.

Mendelevium was discovered by bombarding einsteinium with alpha particles in 1955, the same method still used to produce it today. It was named after Dmitri Mendeleev, father of the periodic table of the chemical elements. Using available microgram quantities of the isotope einsteinium-253, over a million mendelevium atoms may be produced each hour. The chemistry of mendelevium is typical for the late actinides, with a preponderance of the +3 oxidation state but also an accessible +2 oxidation state. Owing to the small amounts of produced mendelevium and all of its isotopes having relatively short half-lives, there are currently no uses for it outside basic scientific research.

Moscovium

Moscovium is a synthetic chemical element with the 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 the 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 period 7.

Roentgenium

Roentgenium is a chemical element with the symbol Rg and atomic number 111. It is an extremely radioactive synthetic element that can be created in a laboratory but is not found in nature. The most stable known isotope, roentgenium-282, has a half-life of 100 seconds, although the unconfirmed roentgenium-286 may have a longer half-life of about 10.7 minutes. Roentgenium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the physicist Wilhelm Röntgen (also spelled Roentgen), who discovered X-rays.

In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and is placed in the group 11 elements, although no chemical experiments have been carried out to confirm that it behaves as the heavier homologue to gold in group 11 as the ninth member of the 6d series of transition metals. Roentgenium is calculated to have similar properties to its lighter homologues, copper, silver, and gold, although it may show some differences from them.

Rutherfordium

Rutherfordium is a synthetic chemical element with the symbol Rf and atomic number 104, named after New Zealand physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be created in a laboratory. It is radioactive; the most stable known isotope, 267Rf, has a half-life of approximately 1.3 hours.

In the periodic table of the elements, it is a d-block element and the second of the fourth-row transition elements. It is a member of the 7th period and belongs to the group 4 elements. Chemistry experiments have confirmed that rutherfordium behaves as the heavier homologue to hafnium in group 4. The chemical properties of rutherfordium are characterized only partly. They compare well with the chemistry of the other groupthe 4 elements, even though some calculations had indicated that the element might show significantly different properties due to relativistic effects.

In the 1960s, small amounts of rutherfordium were produced in the Joint Institute for Nuclear Research in the former Soviet Union and at Lawrence Berkeley National Laboratory in California. 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 rutherfordium as the official name for the element.

Seaborgium

Seaborgium is a synthetic chemical element with the 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.

The Skylark of Space

The Skylark of Space is a science fiction novel by American writer Edward E. "Doc" Smith, written between 1915 and 1921 while Smith was working on his doctorate. Though the original idea for the novel was Smith's, he co-wrote the first part of the novel with Lee Hawkins Garby, the wife of his college classmate and later neighbor Carl Garby. The novel starts as an edisonade, but turns into a space travel adventure when the characters goes into deep space. The Skylark of Space is considered to be one of the earliest novels of interstellar travel and the first example of space opera. Originally serialized in 1928 in the magazine Amazing Stories, it was first published in book form in 1946 by the Buffalo Book Co. The novel was followed by three sequels, beginning with Skylark Three.

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