Transactinide Element
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Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, are the
chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
s with
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
greater than 103. The superheavy elements are those beyond the
actinide The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
s in the periodic table; the last actinide is
lawrencium Lawrencium is a synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radio ...
(atomic number 103). By definition, superheavy elements are also
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. ...
s, i.e., having atomic numbers greater than that of
uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
(92). Depending on the definition of
group 3 Group 3 may refer to: *Group 3 element, chemical element classification *Group 3 (racing), FIA classification for auto racing * Group 3, the third tier of races in worldwide Thoroughbred horse racing * Group 3 image format, Group 3 & Group 4 are ...
adopted by authors, lawrencium may also be included to complete the 6d series.
Glenn T. Seaborg Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...
first proposed the
actinide concept In nuclear chemistry, the actinide concept proposed that the actinides form a second inner transition series homologous to the lanthanides. Its origins stem from observation of lanthanide-like properties in transuranic elements in contrast to the d ...
, which led to the acceptance of the
actinide series The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
. He also proposed a transactinide series ranging from element 104 to 121 and a superactinide series approximately spanning elements 122 to 153 (although more recent work suggests the end of the superactinide series to occur at element 157 instead). The transactinide
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 als ...
was named in his honor. Superheavy elements are
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
and have only been obtained synthetically in laboratories. No macroscopic sample of any of these elements have ever been produced. Superheavy elements are all named after physicists and chemists or important locations involved in the synthesis of the elements.
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
defines an element to exist if its lifetime is longer than 10−14
second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
, which is the time it takes for the atom to form an electron cloud. The known superheavy elements form part of the 6d and 7p series in the periodic table. Except for
rutherfordium Rutherfordium is a chemical element with the symbol Rf and atomic number 104, named after New Zealand-born British physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be made in a laboratory. It is radioactiv ...
and
dubnium Dubnium is a Synthetic element, synthetic chemical element with the Symbol (chemistry), symbol Db and atomic number 105. It is highly radioactive: the most stable known isotopes of dubnium, isotope, dubnium-268, has a half-life of about 16 ho ...
(and lawrencium if it is included), even the longest-lasting isotopes of superheavy elements have
half-lives Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of minutes or less. The
element naming controversy 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 o ...
involved elements
102 102 may refer to: * 102 (number), the number * AD 102, a year in the 2nd century AD * 102 BC, a year in the 2nd century BC * 102 (ambulance service), an emergency medical transport service in Uttar Pradesh, India * 102 (Clyde) Field Squadron, Royal ...
109. Some of these elements thus used systematic names for many years after their discovery was confirmed. (Usually the systematic names are replaced with permanent names proposed by the discoverers relatively shortly after a discovery has been confirmed.)


Introduction


Synthesis of superheavy nuclei

A superheavy
atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron i ...
is created in a nuclear reaction that combines two other nuclei of unequal size into one; roughly, the more unequal the two nuclei in terms of mass, the greater the possibility that the two react. The material made of the heavier nuclei is made into a target, which is then bombarded by the
beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...
of lighter nuclei. Two nuclei can only
fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
into one if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due to
electrostatic repulsion Electrostatics is a branch of physics that studies electric charges at rest ( static electricity). Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for a ...
. The
strong interaction The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the n ...
can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatly accelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus. The energy applied to the beam nuclei to accelerate them can cause them to reach speeds as high as one-tenth of the
speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...
. However, if too much energy is applied, the beam nucleus can fall apart. Coming close enough alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for approximately 10−20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus. This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed. Each pair of a target and a beam is characterized by its
cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...
—the probability that fusion will occur if two nuclei approach one another expressed in terms of the transverse area that the incident particle must hit in order for the fusion to occur. This fusion may occur as a result of the quantum effect in which nuclei can
tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...
through electrostatic repulsion. If the two nuclei can stay close for past that phase, multiple nuclear interactions result in redistribution of energy and an energy equilibrium. The resulting merger is an excited state—termed a
compound nucleus In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation ...
—and thus it is very unstable. To reach a more stable state, the temporary merger may fission without formation of a more stable nucleus. Alternatively, the compound nucleus may eject a few
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s, which would carry away the excitation energy; if the latter is not sufficient for a neutron expulsion, the merger would produce a
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
. This happens in approximately 10−16 seconds after the initial nuclear collision and results in creation of a more stable nucleus. The definition by the
IUPAC/IUPAP Joint Working Party The IUPAC/IUPAP Joint Working Party is a group convened periodically by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) to consider claims for discovery and naming of new ...
(JWP) states that a
chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
can only be recognized as discovered if a nucleus of it has not decayed within 10−14 seconds. This value was chosen as an estimate of how long it takes a nucleus to acquire its outer
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...
s and thus display its chemical properties.


Decay and detection

The beam passes through the target and reaches the next chamber, the separator; if a new nucleus is produced, it is carried with this beam. In the separator, the newly produced nucleus is separated from other nuclides (that of the original beam and any other reaction products) and transferred to a surface-barrier detector, which stops the nucleus. The exact location of the upcoming impact on the detector is marked; also marked are its energy and the time of the arrival. The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long. The nucleus is recorded again once its decay is registered, and the location, the
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
, and the time of the decay are measured. Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, its influence on the outermost
nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number). Until the 1960s, nucleons were ...
s (
proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
s and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, and its range is not limited. Total
binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...
provided by the strong interaction increases linearly with the number of nucleons, whereas electrostatic repulsion increases with the square of the atomic number, i.e. the latter grows faster and becomes increasingly important for heavy and superheavy nuclei. Superheavy nuclei are thus theoretically predicted and have so far been observed to predominantly decay via decay modes that are caused by such repulsion:
alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...
and
spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...
. Almost all alpha emitters have over 210 nucleons, and the lightest nuclide primarily undergoing spontaneous fission has 238. In both decay modes, nuclei are inhibited from decaying by corresponding energy barriers for each mode, but they can be tunnelled through. Alpha particles are commonly produced in radioactive decays because mass of an alpha particle per nucleon is small enough to leave some energy for the alpha particle to be used as kinetic energy to leave the nucleus. Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning. As the atomic number increases, spontaneous fission rapidly becomes more important: spontaneous fission partial half-lives decrease by 23 orders of magnitude from
uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
(element 92) to
nobelium Nobelium is a synthetic chemical element with the symbol No and atomic number 102. It is named in honor of Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranic element and is the penul ...
(element 102), and by 30 orders of magnitude from
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
(element 90) to
fermium Fermium is a synthetic element with the symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic qua ...
(element 100). The earlier
liquid drop model In nuclear physics, the semi-empirical mass formula (SEMF) (sometimes also called the Weizsäcker formula, Bethe–Weizsäcker formula, or Bethe–Weizsäcker mass formula to distinguish it from the Bethe–Weizsäcker process) is used to approxi ...
thus suggested that spontaneous fission would occur nearly instantly due to disappearance of the
fission barrier In nuclear physics and nuclear chemistry, the fission barrier is the activation energy required for a atomic nucleus, nucleus of an atom to undergo Nuclear fission, fission. This barrier may also be defined as the minimum amount of energy require ...
for nuclei with about 280 nucleons. The later
nuclear shell model In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell m ...
suggested that nuclei with about 300 nucleons would form an island of stability in which nuclei will be more resistant to spontaneous fission and will primarily undergo alpha decay with longer half-lives. Subsequent discoveries suggested that the predicted island might be further than originally anticipated; they also showed that nuclei intermediate between the long-lived actinides and the predicted island are deformed, and gain additional stability from shell effects. Experiments on lighter superheavy nuclei, as well as those closer to the expected island, have shown greater than previously anticipated stability against spontaneous fission, showing the importance of shell effects on nuclei. Alpha decays are registered by the emitted alpha particles, and the decay products are easy to determine before the actual decay; if such a decay or a series of consecutive decays produces a known nucleus, the original product of a reaction can be easily determined. (That all decays within a decay chain were indeed related to each other is established by the location of these decays, which must be in the same place.) The known nucleus can be recognized by the specific characteristics of decay it undergoes such as decay energy (or more specifically, the
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
of the emitted particle). Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters. The information available to physicists aiming to synthesize a superheavy element is thus the information collected at the detectors: location, energy, and time of arrival of a particle to the detector, and those of its decay. The physicists analyze this data and seek to conclude that it was indeed caused by a new element and could not have been caused by a different nuclide than the one claimed. Often, provided data is insufficient for a conclusion that a new element was definitely created and there is no other explanation for the observed effects; errors in interpreting data have been made.


History


Early predictions

The heaviest element known at the end of the 19th century was uranium, with an
atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&nbs ...
of approximately 240 (now known to be 238)  amu. Accordingly, it was placed in the last row of the periodic table; this fueled speculation about the possible existence of elements heavier than uranium and why ''A'' = 240 seemed to be the limit. Following the discovery of the
noble gases The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
, beginning with that of
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
in 1895, the possibility of heavier members of the group was considered. Danish chemist Julius Thomsen proposed in 1895 the existence of a sixth noble gas with ''Z'' = 86, ''A'' = 212 and a seventh with ''Z'' = 118, ''A'' = 292, the last closing a 32-element
period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...
containing
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
and uranium. In 1913, Swedish physicist
Johannes Rydberg Johannes (Janne) Robert Rydberg (; 8 November 1854 – 28 December 1919) was a Swedish physicist mainly known for devising the Rydberg formula, in 1888, which is used to describe the wavelengths of photons (of visible light and other electrom ...
extended Thomsen's extrapolation of the periodic table to include even heavier elements with atomic numbers up to 460, but he did not believe that these superheavy elements existed or occurred in nature. In 1914, German physicist Richard Swinne proposed that elements heavier than uranium, such as those around ''Z'' = 108, could be found in
cosmic rays Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
. He suggested that these elements may not necessarily have decreasing half-lives with increasing atomic number, leading to speculation about the possibility of some longer-lived elements at Z = 98–102 and Z = 108–110 (though separated by short-lived elements). Swinne published these predictions in 1926, believing that such elements might exist in the
Earth's core The internal structure of Earth is the solid portion of the Earth, excluding its atmosphere and hydrosphere. The structure consists of an outer silicate solid crust, a highly viscous asthenosphere and solid mantle, a liquid outer core whose ...
, in
iron meteorites Iron meteorites, also known as siderites, or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron met ...
, or in the
ice caps of Greenland Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opa ...
where they had been locked up from their supposed cosmic origin.


Discoveries

Work performed from 1961 to 2013 at four labs – the
Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States Department of Energy National Labs, United States national laboratory that is owned by, and conducts scientific research on behalf of, t ...
in the US, the
Joint Institute for Nuclear Research The Joint Institute for Nuclear Research (JINR, russian: Объединённый институт ядерных исследований, ОИЯИ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research c ...
in the USSR (later Russia), the
GSI Helmholtz Centre for Heavy Ion Research The GSI Helmholtz Centre for Heavy Ion Research (german: GSI Helmholtzzentrum für Schwerionenforschung) is a federally and state co-funded heavy ion () research center in the Wixhausen suburb of Darmstadt, Germany. It was founded in 1969 as th ...
in Germany, and Riken in Japan – identified and confirmed the elements
lawrencium Lawrencium is a synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radio ...
to
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, Russia, by a joint team of Russian and American scient ...
according to the criteria of the
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
IUPAP The International Union of Pure and Applied Physics (IUPAP ) is an international non-governmental organization whose mission is to assist in the worldwide development of physics, to foster international cooperation in physics, and to help in the ...
Transfermium Working Groups and subsequent Joint Working Parties. These discoveries complete the seventh row of the periodic table. The remaining two transactinides,
ununennium Ununennium, also known as eka-francium or element 119, is the hypothetical chemical element with symbol Uue and atomic number 119. ''Ununennium'' and ''Uue'' are the temporary systematic IUPAC name and symbol respectively, which are used until th ...
(''Z'' = 119) and
unbinilium Unbinilium, also known as eka-radium or simply element 120, is the hypothetical chemical element in the periodic table with symbol Ubn and atomic number 120. ''Unbinilium'' and ''Ubn'' are the temporary systematic IUPAC name and symbol, which ar ...
(''Z'' = 120), have not yet been synthesized. They would begin an eighth period.


List of elements

*103
Lawrencium Lawrencium is a synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radio ...
, Lr (for
Ernest Lawrence Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American nuclear physicist and winner of the Nobel Prize in Physics in 1939 for his invention of the cyclotron. He is known for his work on uranium-isotope separation fo ...
); sometimes but not always included *104
Rutherfordium Rutherfordium is a chemical element with the symbol Rf and atomic number 104, named after New Zealand-born British physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be made in a laboratory. It is radioactiv ...
, Rf (for
Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest ...
) *105
Dubnium Dubnium is a Synthetic element, synthetic chemical element with the Symbol (chemistry), symbol Db and atomic number 105. It is highly radioactive: the most stable known isotopes of dubnium, isotope, dubnium-268, has a half-life of about 16 ho ...
, Db (for the town of
Dubna Dubna ( rus, Дубна́, p=dʊbˈna) is a town in Moscow Oblast, Russia. It has a status of ''naukograd'' (i.e. town of science), being home to the Joint Institute for Nuclear Research, an international nuclear physics research center and one o ...
, near
Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 million ...
) *106
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 als ...
, Sg (for
Glenn T. Seaborg Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...
) *107 Bohrium, Bh (for
Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. B ...
) *108
Hassium Hassium is a chemical element with the symbol Hs and the atomic number 108. Hassium is highly radioactive; its most stable known isotopes have half-lives of approximately ten seconds. One of its isotopes, 270Hs, has magic numbers of both protons ...
, Hs (for Hassia /nowiki>Hesse.html" ;"title="Hesse.html" ;"title="/nowiki>Hesse">/nowiki>Hesse">Hesse.html" ;"title="/nowiki>Hesse">/nowiki>Hesse/nowiki>, location of Darmstadt) *109 Meitnerium, Mt (for Lise Meitner) *110 Darmstadtium, Ds (for Darmstadt) *111 Roentgenium, Rg (for Wilhelm Röntgen) *112 Copernicium, Cn (for Nicolaus Copernicus) *113
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 ...
, Nh (for Nihon /nowiki>Japan.html" ;"title="Japan.html" ;"title="/nowiki>Japan">/nowiki>Japan">Japan.html" ;"title="/nowiki>Japan">/nowiki>Japan/nowiki>, location of the Riken institute) *114 Flerovium, Fl (for Russian physicist Georgy Flyorov) *115 Moscovium, Mc (for
Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 million ...
) *116
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 a laboratory setting and has not been observed in nature. The element is named afte ...
, Lv (for
Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory (LLNL) is a federal research facility in Livermore, California, United States. The lab was originally established as the University of California Radiation Laboratory, Livermore Branch in 1952 in response ...
) *117
Tennessine Tennessine is a synthetic chemical element with the 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 ann ...
, Ts (for
Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...
, location of
Oak Ridge National Laboratory Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research an ...
) *118
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, Russia, by a joint team of Russian and American scient ...
, Og (for Russian physicist
Yuri Oganessian Yuri Tsolakovich Oganessian (russian: Юрий Цолакович Оганесян ; ''Yuri Ts'olaki Hovhannisyan'' . Oganessian is the Russified version of the Armenian last name Hovhannisyan. The article on Oganessian in the ''Armenian Sovie ...
)


Characteristics

Due to their short half-lives (for example, the most stable known isotope of seaborgium has a half-life of 14 minutes, and half-lives decrease gradually with increasing atomic number) and the low yield of the
nuclear reactions In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation o ...
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 Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of ...
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. Elements 103 to 112, lawrencium to copernicium, may be taken to form the 6d series of transition elements. Experimental evidence shows that elements 103–108 behave as expected for their position in the periodic table, as heavier homologues of lutetium through osmium. They are expected to have
ionic radii Ionic radius, ''r''ion, is the radius of a monatomic ion in an ionic crystal structure. Although neither atoms nor ions have sharp boundaries, they are treated as if they were hard spheres with radii such that the sum of ionic radii of the cation ...
between those of their 5d transition metal homologs and their
actinide The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
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. Elements 113 to 118, nihonium to 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 The inert-pair effect is the tendency of the two electrons in the outermost atomic ''s''-orbital to remain unshared in compounds of post-transition metals. The term ''inert-pair effect'' is often used in relation to the increasing stability of oxi ...
. 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). Element 118 is the last element that has been synthesized. The next two elements, element 119 and element 120, should form an 8s series and be an
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
and
alkaline earth metal The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...
respectively. The 8s electrons are expected to be relativistically stabilized, so that the trend toward higher reactivity down these groups will reverse and the elements will behave more like their period 5 homologs,
rubidium Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density higher ...
and
strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
. Still 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 unit Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danes, Danish physicist who made foundational contributions to understanding atomic structure and old quantum theory, quantum theory, for which he received the Nobel ...
s in element 120 in the excited g5g1 8s1 configuration to 0.8 Bohr units in element 121 in the excited g5g1 7d1 8s1 configuration, in a phenomenon called "radial collapse". Element 122 should add either a further 7d or a further 8p electron to element 121's electron configuration. Elements 121 and 122 should be similar to
actinium Actinium is a chemical element with the symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name ''emanium''; the element got its name by being wrongly identified with a substance An ...
and
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
respectively. At element 121, the
superactinide An extended periodic table theorises about chemical elements beyond those currently known in the periodic table and proven. , the element with the highest atomic number known is oganesson (''Z'' = 118), which completes the seventh period (row ...
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 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 Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...
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; element 164 is expected to mix characteristics of the elements of
group 10 Group 10, numbered by current IUPAC style, is the group of chemical elements in the periodic table that consists of nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds). All are d-block transition metals. All known isotopes of darm ...
, 12, and 18.


Beyond superheavy elements

It has been suggested that elements beyond ''Z'' = 126 be called ''beyond superheavy elements''.


See also

*
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter that is typically formed when a gas of bosons at very low densities is cooled to temperatures very close to absolute zero (−273.15 °C or −459.67&n ...
(also known as ''Superatom'')


Notes


References


Bibliography

*
pp. 030001-1–030001-17pp. 030001-18–030001-138, Table I. The NUBASE2016 table of nuclear and decay properties
* * * * {{Authority control Nuclear physics Sets of chemical elements Synthetic elements