Nihonium is a
synthetic chemical element; it has
symbol
A symbol is a mark, Sign (semiotics), sign, or word that indicates, signifies, or is understood as representing an idea, physical object, object, or wikt:relationship, relationship. Symbols allow people to go beyond what is known or seen by cr ...
Nh and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...
113. It is extremely
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 conside ...
: its most stable known
isotope
Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...
, nihonium-286, has a
half-life Half-life is a mathematical and scientific description of exponential or gradual decay.
Half-life, half life or halflife may also refer to:
Film
* Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang
* ''Half Life: ...
of about 10 seconds. In the
periodic table
The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...
, nihonium is a
transactinide element
Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...
in the
p-block
A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term seems to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-bl ...
. It is a member of
period 7 and
group 13.
Nihonium was first reported to have been created in experiments carried out between 14 July and 10 August 2003, by a Russian–American collaboration at the
Joint Institute for Nuclear Research
The Joint Institute for Nuclear Research (JINR, ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research center for nuclear sciences, with 5,500 staff members including 1,200 researchers holding over 1,000 ...
(JINR) in
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 o ...
, Russia, working in collaboration with the
Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
in
Livermore, California
Livermore is a city in Alameda County, California. With a 2020 population of 87,955, Livermore is the most populous city in the Tri-Valley, giving its name to the Livermore Valley. It is located on the eastern edge of California's San Francisc ...
, and on 23 July 2004, by a team of Japanese scientists at
Riken
is a national scientific research institute in Japan. Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama, Wakō, Saitama Prefecture, on the outskirts of Tokyo. Riken is a ...
in
Wakō, Japan. The confirmation of their claims in the ensuing years involved independent teams of scientists working in the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
,
Germany
Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
,
Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
, and
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
, 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. 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 .
Very little is known about nihonium, as it has been made only in very small amounts that decay within seconds. The anomalously long lives of some superheavy nuclides, including some nihonium isotopes, are explained by the
island of stability
In nuclear physics, the island of stability is a predicted set of isotopes of superheavy elements that may have considerably longer half-lives than known isotopes of these elements. It is predicted to appear as an "island" in the chart of nuclid ...
theory. Experiments to date have supported the theory, with the half-lives of the confirmed nihonium isotopes increasing from milliseconds to seconds as
neutron
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...
s are added and the island is approached. Nihonium has been calculated to have similar properties to its homologues
boron
Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...
,
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
,
gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
,
indium
Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
, and
thallium
Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...
. All but boron are
post-transition metal
The metallic elements in the periodic table located between the transition metals to their left and the chemically weak nonmetallic metalloids to their right have received many names in the literature, such as post-transition metals, poor metal ...
s, 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
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
than the +3 state, like thallium, but in the +1 state nihonium should behave more like
silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
and
astatine
Astatine is a chemical element; it has Symbol (chemistry), symbol At and atomic number 85. It is the abundance of elements in Earth's crust, rarest naturally occurring element in the Earth's crust, occurring only as the Decay chain, decay product ...
than thallium. Preliminary experiments have shown that elemental nihonium is not very
volatile, and that it is less reactive than its lighter homologue thallium.
Introduction
History
Early indications
The syntheses of elements
107 107 may refer to:
*107 (number), the number
*AD 107, a year in the 2nd century AD
*107 BC, a year in the 2nd century BC
*107 (New Jersey bus)
*107 Camilla, a main-belt asteroid
*Peugeot 107, a city car
See also
*10/7 (disambiguation)
*Bohrium, ...
to
112 were conducted at the
GSI Helmholtz Centre for Heavy Ion Research
The GSI Helmholtz Centre for Heavy Ion Research () is a federally and state co-funded heavy ion () research center in Darmstadt, Germany. It was founded in 1969 as the Society for Heavy Ion Research (), abbreviated GSI, to conduct research on a ...
in
Darmstadt
Darmstadt () is a city in the States of Germany, state of Hesse in Germany, located in the southern part of the Frankfurt Rhine Main Area, Rhine-Main-Area (Frankfurt Metropolitan Region). Darmstadt has around 160,000 inhabitants, making it the ...
, Germany, from 1981 to 1996. These elements were made by cold fusion reactions, in which targets made of
lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
and
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
, which are around the
stable configuration of 82 protons, are bombarded with heavy ions of
period 4 element
A period 4 element is one of the chemical elements in the fourth row (or Period (periodic table), period) of the periodic table, periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) tr ...
s. This creates fused nuclei with low excitation energies due to the stability of the targets' nuclei, significantly increasing the yield of
superheavy element
Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...
s. Cold fusion was pioneered by
Yuri Oganessian
Yuri Tsolakovich Oganessian (born 14 April 1933) is an Armenian and Russian nuclear physicist who is best known as a researcher of superheavy elements. He has led the discovery of multiple chemical elements. He succeeded Georgy Flyorov as dir ...
and his team in 1974 at the
Joint Institute for Nuclear Research
The Joint Institute for Nuclear Research (JINR, ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research center for nuclear sciences, with 5,500 staff members including 1,200 researchers holding over 1,000 ...
(JINR) in
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 o ...
, Soviet Union. Yields from cold fusion reactions were found to decrease significantly with increasing atomic number; the resulting nuclei were severely neutron-deficient and short-lived. The GSI team attempted to synthesise element 113 via cold fusion in 1998 and 2003, bombarding bismuth-209 with
zinc
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
-70; both attempts were unsuccessful.
Faced with this problem,
Oganessian and his team at the
JINR turned their renewed attention to the older hot fusion technique, in which heavy
actinide
The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...
targets were bombarded with lighter ions.
Calcium-48 was suggested as an ideal projectile, because it is very neutron-rich for a light element (combined with the already neutron-rich actinides) and would minimise the neutron deficiencies of the nuclides produced. Being
doubly magic, it would confer benefits in stability to the fused nuclei. In collaboration with the team at the
Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
(LLNL) in
Livermore, California
Livermore is a city in Alameda County, California. With a 2020 population of 87,955, Livermore is the most populous city in the Tri-Valley, giving its name to the Livermore Valley. It is located on the eastern edge of California's San Francisc ...
, United States, they made an attempt on
element 114 (which was predicted to be a
magic number, closing a proton shell, and more stable than element 113).
In 1998, the JINR–LLNL collaboration started their attempt on element 114, bombarding a target of
plutonium-244
Plutonium-244 (Pu) is an isotope of plutonium that has a half-life of 81.3 million years. This is longer than any other isotope of plutonium and longer than any other known isotope of an element beyond bismuth, except for the three naturally abu ...
with ions of calcium-48:
: + →
292114* →
290114 + 2 + e
− →
290113 +
νe ?
A single
atom
Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
was observed which was thought to be the isotope
289114: the results were published in January 1999.
Despite numerous attempts to repeat this reaction, an isotope with these decay properties has never again been found, and the exact identity of this activity is unknown.
A 2016 paper by
Sigurd Hofmann
Sigurd Hofmann (15 February 1944 – 17 June 2022) was a German physicist known for his work on superheavy elements.
Biography
Hofmann was born in Böhmisch Kamnitz, Nazi Germany (now Česká Kamenice, Czech Republic) on 15 February 1944. He d ...
et al. considered that the most likely explanation of the 1998 result is that two neutrons were emitted by the produced compound nucleus, leading to
290114 and
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...
to
290113, while more neutrons were emitted in all other produced chains. This would have been the first report of a decay chain from an isotope of element 113, but it was not recognised at the time, and the assignment is still uncertain.
A similar long-lived activity observed by the JINR team in March 1999 in the
242Pu +
48Ca reaction may be due to the electron-capture daughter of
287114,
287113; this assignment is also tentative.
JINR–LLNL collaboration
The now-confirmed discovery of element 114 was made in June 1999 when the JINR team repeated the first
244Pu +
48Ca reaction from 1998;
following this, the JINR team used the same hot fusion technique to synthesize elements
116 and
118 in 2000 and 2002 respectively via the
248 Cm +
48Ca and
249 Cf +
48Ca reactions. They then turned their attention to the missing odd-numbered elements, as the odd protons and possibly neutrons would hinder decay by
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
and result in longer decay chains.
The first report of element 113 was in August 2003, when it was identified as an
alpha decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...
product of
element 115. Element 115 had been produced by bombarding a target of
americium
Americium is a synthetic element, synthetic chemical element; it has Chemical symbol, symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element e ...
-243 with calcium-48 projectiles. The
JINR–
LLNL
Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
collaboration published its results in February 2004:
: + →
291115* →
288115 + 3 →
284113 +
: + →
291115* →
287115 + 4 →
283113 +
Four further alpha decays were observed, ending with the
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
of isotopes of element 105,
dubnium
Dubnium is a synthetic element, synthetic chemical element; it has Chemical symbol, 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 hours. ...
.
Riken
While the JINR–LLNL collaboration had been studying fusion reactions with
48Ca, a team of Japanese scientists at the
Riken
is a national scientific research institute in Japan. Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama, Wakō, Saitama Prefecture, on the outskirts of Tokyo. Riken is a ...
Nishina Center for Accelerator-Based Science in
Wakō, Japan, led by
Kōsuke Morita had been studying cold fusion reactions. Morita had previously studied the synthesis of superheavy elements at the JINR before starting his own team at Riken. In 2001, his team confirmed the GSI's discoveries of elements
108,
110,
111, and 112. They then made a new attempt on element 113, using the same
209Bi +
70Zn reaction that the GSI had attempted unsuccessfully in 1998. Despite the much lower yield expected than for the JINR's hot fusion technique with calcium-48, the Riken team chose to use cold fusion as the synthesised isotopes would alpha decay to known daughter nuclides and make the discovery much more certain, and would not require the use of radioactive targets. In particular, the isotope
278113 expected to be produced in this reaction would decay to the known
266Bh, which had been synthesised in 2000 by a team at the
Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory (LBNL, Berkeley Lab) is a Federally funded research and development centers, federally funded research and development center in the Berkeley Hills, hills of Berkeley, California, United States. Established i ...
(LBNL) in Berkeley.
The bombardment of
209Bi with
70Zn at Riken began in September 2003.
The team detected a single atom of
278113 in July 2004 and published their results that September:
: + →
279113* →
278113 +
The
Riken
is a national scientific research institute in Japan. Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama, Wakō, Saitama Prefecture, on the outskirts of Tokyo. Riken is a ...
team observed four alpha decays from
278113, creating a decay chain passing through
274Rg,
270Mt, and
266Bh before terminating with the spontaneous fission of
262Db.
The decay data they observed for the alpha decay of
266Bh matched the 2000 data, lending support for their claim.
Spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
of its daughter
262Db had not been previously known; the American team had observed only alpha decay from this nuclide.
Road to confirmation
When the discovery of a new element is claimed, the
Joint Working Party (JWP) of the
International Union of Pure and Applied Chemistry
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 ...
(IUPAC) and the
International Union of Pure and Applied Physics
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 ...
(IUPAP) assembles to examine the claims according to their criteria for the discovery of a new element, and decides
scientific priority
In science, priority is the credit given to the individual or group of individuals who first made the discovery or proposed the theory. Fame and honours usually go to the first person or group to publish a new finding, even if several researchers a ...
and naming rights for the elements. According to the JWP criteria, a discovery must demonstrate that the element has an atomic number different from all previously observed values. It should also preferably be repeated by other laboratories, although this requirement has been waived where the data is of very high quality. Such a demonstration must establish properties, either physical or chemical, of the new element and establish that they are those of a previously unknown element. The main techniques used to demonstrate atomic number are cross-reactions (creating claimed
nuclides
Nuclides (or nucleides, from nucleus, also known as nuclear species) are a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state.
The word ''nuclide'' was coined by the Am ...
as parents or daughters of other nuclides produced by a different reaction) and anchoring decay chains to known daughter nuclides. For the JWP, priority in confirmation takes precedence over the date of the original claim. Both teams set out to confirm their results by these methods.
2004–2008
In June 2004 and again in December 2005, the JINR–LLNL collaboration strengthened their claim for the discovery of element 113 by conducting chemical experiments on
268 Db, the final
decay product
In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( d ...
of
288115. This was valuable as none of the nuclides in this decay chain were previously known, so that their claim was not supported by any previous experimental data, and chemical experimentation would strengthen the case for their claim, since the chemistry of dubnium is known.
268Db was successfully identified by extracting the final decay products, measuring
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
(SF) activities and using chemical identification techniques to confirm that they behave like a
group 5 element
Group 5 is a group of elements in the periodic table. Group 5 contains vanadium (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-block of the periodic table. This group is sometimes called the vanadium group or van ...
(dubnium is known to be in group 5).
Both the half-life and decay mode were confirmed for the proposed
268Db which lends support to the assignment of the parent and
daughter nuclei to elements 115 and 113 respectively.
Further experiments at the JINR in 2005 confirmed the observed decay data.
In November and December 2004, the Riken team studied the
205Tl +
70Zn reaction, aiming the zinc beam onto a
thallium
Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...
rather than a bismuth target, in an effort to directly produce
274Rg in a cross-bombardment as it is the immediate daughter of
278113. The reaction was unsuccessful, as the thallium target was
physically weak compared to the more commonly used lead and bismuth targets, and it deteriorated significantly and became non-uniform in thickness. The reasons for this weakness are unknown, given that thallium has a higher melting point than bismuth.
The Riken team then repeated the original
209Bi +
70Zn reaction and produced a second atom of
278113 in April 2005, with a decay chain that again terminated with the spontaneous fission of
262Db. The decay data were slightly different from those of the first chain: this could have been because an
alpha particle
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...
escaped from the detector without depositing its full energy, or because some of the intermediate decay products were formed in
metastable isomeric states.
In 2006, a team at the Heavy Ion Research Facility in
Lanzhou
Lanzhou is the capital and largest city of Gansu province in northwestern China. Located on the banks of the Yellow River, it is a key regional transportation hub, connecting areas further west by rail to the eastern half of the country. His ...
, China, investigated the
243Am +
26Mg reaction, producing four atoms of
266Bh. All four chains started with an alpha decay to
262Db; three chains ended there with spontaneous fission, as in the
278113 chains observed at Riken, while the remaining one continued via another alpha decay to
258Lr, as in the
266Bh chains observed at LBNL.
In June 2006, the JINR–LLNL collaboration claimed to have synthesised a new isotope of element 113 directly by bombarding a
neptunium
Neptunium is a chemical element; it has chemical symbol, symbol Np and atomic number 93. A radioactivity, radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar Syste ...
-237 target with accelerated calcium-48 nuclei:
: + →
285113* →
282113 + 3
Two atoms of
282113 were detected. The aim of this experiment had been to synthesise the isotopes
281113 and
282113 that would fill in the gap between isotopes produced via hot fusion (
283113 and
284113) and cold fusion (
278113). After five alpha decays, these nuclides would reach known isotopes of
lawrencium
Lawrencium is a synthetic chemical element; it has symbol Lr (formerly Lw) and atomic number 103. It is named after Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radioactiv ...
, assuming that the decay chains were not terminated prematurely by spontaneous fission. The first decay chain ended in fission after four alpha decays, presumably originating from
266Db or its electron-capture daughter
266Rf.
Spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
was not observed in the second chain even after four alpha decays. A fifth alpha decay in each chain could have been missed, since
266Db can theoretically undergo alpha decay, in which case the first decay chain would have ended at the known
262Lr or
262No and the second might have continued to the known long-lived
258Md, which has a half-life of 51.5 days, longer than the duration of the experiment: this would explain the lack of a spontaneous fission event in this chain. In the absence of direct detection of the long-lived
alpha decays, these interpretations remain unconfirmed, and there is still no known link between any superheavy nuclides produced by hot fusion and the well-known main body of the chart of nuclides.
2009–2015
The JWP published its report on elements 113–116 and 118 in 2011. It recognised the JINR–LLNL collaboration as having discovered elements 114 and 116, but did not accept either team's claim to element 113 and did not accept the JINR–LLNL claims to elements 115 and 118. The JINR–LLNL claim to elements 115 and 113 had been founded on chemical identification of their daughter dubnium, but the JWP objected that current theory could not distinguish between superheavy
group 4 Group 4 may refer to:
*Group 4 element
Group 4 is the second group of transition metals in the periodic table. It contains only the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). The group is also called the t ...
and group 5 elements by their chemical properties with enough confidence to allow this assignment.
The decay properties of all the nuclei in the decay chain of element 115 had not been previously characterised before the JINR experiments, a situation which the JWP generally considers "troublesome, but not necessarily exclusive", and with the small number of atoms produced with neither known daughters nor cross-reactions the JWP considered that their criteria had not been fulfilled.
The JWP did not accept the Riken team's claim either due to inconsistencies in the decay data, the small number of atoms of element 113 produced, and the lack of unambiguous anchors to known isotopes.
In early 2009, the Riken team synthesised the decay product
266Bh directly in the
248Cm +
23Na reaction to establish its link with
278113 as a cross-bombardment. They also established the branched decay of
262Db, which sometimes underwent spontaneous fission and sometimes underwent the previously known alpha decay to
258Lr.
In late 2009, the JINR–LLNL collaboration studied the
249Bk +
48Ca reaction in an effort to produce
element 117, which would decay to elements 115 and 113 and bolster their claims in a cross-reaction. They were now joined by scientists from
Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) is a federally funded research and development centers, federally funded research and development center in Oak Ridge, Tennessee, United States. Founded in 1943, the laboratory is sponsored by the United Sta ...
(ORNL) and
Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private university, private research university in Nashville, Tennessee, United States. Founded in 1873, it was named in honor of shipping and railroad magnate Cornelius Vanderbilt, who provide ...
, both in
Tennessee
Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...
, United States,
who helped procure the rare and highly radioactive
berkelium
Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National ...
target necessary to complete the JINR's calcium-48 campaign to synthesise the heaviest elements on the periodic table.
Two isotopes of element 117 were synthesised, decaying to element 115 and then element 113:
: + →
297117* →
294117 + 3 →
290115 + α →
286113 + α
: + →
297117* →
293117 + 4 →
289115 + α →
285113 + α
The new isotopes
285113 and
286113 produced did not overlap with the previously claimed
282113,
283113, and
284113, so this reaction could not be used as a cross-bombardment to confirm the 2003 or 2006 claims.
In March 2010, the Riken team again attempted to synthesise
274Rg directly through the
205Tl +
70Zn reaction with upgraded equipment; they failed again and abandoned this cross-bombardment route.
After 450 more days of irradiation of bismuth with zinc projectiles, Riken produced and identified another
278113 atom in August 2012.
Although electricity prices had soared since the
2011 Tōhoku earthquake and tsunami
On 11 March 2011, at 14:46:24 Japan Standard Time, JST (05:46:24 UTC), a 9.0–9.1 Submarine earthquake, undersea megathrust earthquake occurred in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region. It lasted approx ...
, and Riken had ordered the shutdown of the accelerator programs to save money, Morita's team was permitted to continue with one experiment, and they chose their attempt to confirm their synthesis of element 113.
In this case, a series of six alpha decays was observed, leading to an isotope of
mendelevium
Mendelevium is a synthetic chemical element; it has symbol Md ( formerly Mv) and atomic number 101. A metallic radioactive transuranium element in the actinide series, it is the first element by atomic number that currently cannot be produced ...
:
:
278113 → + → + → + → + → + → +
This decay chain differed from the previous observations at Riken mainly in the decay mode of
262Db, which was previously observed to undergo spontaneous fission, but in this case instead alpha decayed; the alpha decay of
262Db to
258Lr is
well-known. The team calculated the probability of accidental
coincidence
A coincidence is a remarkable concurrence of events or circumstances that have no apparent causal connection with one another. The perception of remarkable coincidences may lead to supernatural, occult, or paranormal claims, or it may lead to b ...
to be 10
−28, or totally negligible.
The resulting
254Md atom then underwent
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...
to
254 Fm, which underwent the seventh alpha decay in the chain to the long-lived
250 Cf, which has a half-life of around thirteen years.
The
249Bk +
48Ca experiment was repeated at the JINR in 2012 and 2013 with consistent results, and again at the GSI in 2014.
In August 2013, a team of researchers at
Lund University
Lund University () is a Public university, public research university in Sweden and one of Northern Europe's oldest universities. The university is located in the city of Lund in the Swedish province of Scania. The university was officially foun ...
in
Lund
Lund (, ;["Lund"](_blank)
(US) and ) is a city in the provinces of Sweden, province of Scania, southern Swed ...
, Sweden, and at the GSI announced that they had repeated the 2003
243Am +
48Ca experiment, confirming the findings of the JINR–LLNL collaboration.
The same year, the 2003 experiment had been repeated at the JINR, now also creating the isotope
289115 that could serve as a cross-bombardment for confirming their discovery of the
element 117 isotope
293117, as well as its daughter
285113 as part of its decay chain.
Confirmation of
288115 and its daughters was published by the team at the LBNL in August 2015.
Approval of discoveries
In December 2015, the conclusions of a new JWP report were published by IUPAC in a press release, in which element 113 was awarded to Riken; elements 115, 117, and 118 were awarded to the collaborations involving the JINR.
A joint 2016 announcement by IUPAC and IUPAP had been scheduled to coincide with the publication of the JWP reports, but IUPAC alone decided on an early release because the news of Riken being awarded credit for element 113 had been leaked to Japanese newspapers.
For the first time in history, a team of Asian physicists would name a new element.
The JINR considered the awarding of element 113 to Riken unexpected, citing their own 2003 production of elements 115 and 113, and pointing to the precedents of elements
103,
104, and
105 105 may refer to:
*105 (number), the number
* AD 105, a year in the 2nd century AD
* 105 BC, a year in the 2nd century BC
* 105 (telephone number), the emergency telephone number in Mongolia
* 105 (MBTA bus), a Massachusetts Bay Transport Authority ...
where IUPAC had awarded joint credit to the JINR and LBNL. They stated that they respected IUPAC's decision, but reserved determination of their position for the official publication of the JWP reports.
The full JWP reports were published on 21 January 2016. The JWP recognised the discovery of element 113, assigning priority to Riken. They noted that while the individual decay energies of each nuclide in the decay chain of
278113 were inconsistent, their sum was now confirmed to be consistent, strongly suggesting that the initial and final states in
278113 and its daughter
262Db were the same for all three events. The decay of
262Db to
258Lr and
254Md was previously known, firmly anchoring the decay chain of
278113 to known regions of the chart of nuclides. The JWP considered that the JINR–LLNL collaborations of 2004 and 2007, producing element 113 as the daughter of element 115, did not meet the discovery criteria as they had not convincingly determined the atomic numbers of their nuclides through cross-bombardments, which were considered necessary since their decay chains were not anchored to previously known nuclides. They also considered that the previous JWP's concerns over their chemical identification of the dubnium daughter had not been adequately addressed. The JWP recognised the JINR–LLNL–ORNL–Vanderbilt collaboration of 2010 as having discovered elements 117 and 115, and accepted that element 113 had been produced as their daughter, but did not give this work shared credit.
After the publication of the JWP reports, Sergey Dimitriev, the lab director of the Flerov lab at the JINR where the discoveries were made, remarked that he was happy with IUPAC's decision, mentioning the time Riken spent on their experiment and their good relations with Morita, who had learnt the basics of synthesising superheavy elements at the JINR.
The sum argument advanced by the JWP in the approval of the discovery of element 113 was later criticised in a May 2016 study from Lund University and the GSI, as it is only valid if no
gamma decay
Gamma (; uppercase , lowercase ; ) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter normally repr ...
or
internal conversion
Internal conversion is an atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in internal conversion (o ...
takes place along the decay chain, which is not likely for odd nuclei, and the uncertainty of the alpha decay energies measured in the
278113 decay chain was not small enough to rule out this possibility. If this is the case, similarity in lifetimes of intermediate daughters becomes a meaningless argument, as different isomers of the same nuclide can have different half-lives: for example, the ground state of
180Ta has a half-life of hours, but an excited state
180mTa has never been observed to decay. This study found reason to doubt and criticise the IUPAC approval of the discoveries of elements 115 and 117, but the data from Riken for element 113 was found to be congruent, and the data from the JINR team for elements 115 and 113 to probably be so, thus endorsing the IUPAC approval of the discovery of element 113. Two members of the JINR team published a journal article rebutting these criticisms against the congruence of their data on elements 113, 115, and 117 in June 2017.
Naming

Using
Mendeleev's nomenclature for unnamed and undiscovered elements, nihonium would be known as ''eka-thallium''. In 1979, IUPAC published recommendations according to which the element was to be called ''ununtrium'' (with the corresponding symbol of ''Uut''),
a
systematic element name as a
placeholder, until the discovery of the element is confirmed and a name is decided on. The recommendations were widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, but were mostly ignored among scientists in the field, who called it "element 113", with the symbol of ''E113'', ''(113)'', or even simply ''113''.
Before the JWP recognition of their priority, the Japanese team had unofficially suggested various names: ''japonium'', after their home country;
''nishinanium'', after Japanese physicist
Yoshio Nishina, the "founding father of modern physics research in Japan"; and ''rikenium'', after the institute.
After the recognition, the Riken team gathered in February 2016 to decide on a name. Morita expressed his desire for the name to honour the fact that element 113 had been discovered in Japan. ''Japonium'' was considered, making the connection to Japan easy to identify for non-Japanese, but it was rejected as ''
Jap'' is considered an
ethnic slur
The following is a list of ethnic slurs, ethnophaulisms, or ethnic epithets that are, or have been, used as insinuations or allegations about members of a given ethnic, national, or racial group or to refer to them in a derogatory, pej ...
. The name ''nihonium'' was chosen after an hour of deliberation: it comes from , one of the two Japanese pronunciations for the name of Japan. The discoverers also intended to reference the support of their research by the Japanese people (Riken being almost entirely government-funded), recover lost pride and trust in science among those who were affected by the
Fukushima Daiichi nuclear disaster
The Fukushima nuclear accident was a major nuclear accident at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan, which began on 11 March 2011. The cause of the accident was the 2011 Tōhoku earthquake and tsunami, which r ...
,
and honour Japanese chemist
Masataka Ogawa's 1908 discovery of
rhenium
Rhenium is a chemical element; it has symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one ...
, which he named "nipponium" with symbol Np after the other Japanese pronunciation of Japan's name.
As Ogawa's claim had not been accepted, the name "nipponium" could not be reused for a new element, and its symbol Np had since been used for
neptunium
Neptunium is a chemical element; it has chemical symbol, symbol Np and atomic number 93. A radioactivity, radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar Syste ...
. In March 2016, Morita proposed the name "nihonium" to IUPAC, with the symbol Nh.
The naming realised what had been a national dream in Japanese science ever since Ogawa's claim.
The former president of IUPAP,
Cecilia Jarlskog, complained at the Nobel Symposium on Superheavy Elements in
Bäckaskog Castle, Sweden, in June 2016 about the lack of openness involved in the process of approving new elements, and stated that she believed that the JWP's work was flawed and should be redone by a new JWP. A survey of physicists determined that many felt that the Lund–GSI 2016 criticisms of the JWP report were well-founded, but it was also generally thought that the conclusions would hold up if the work was redone. Thus the new president,
Bruce McKellar, ruled that the proposed names should be released in a joint IUPAP–IUPAC press release.
IUPAC and IUPAP publicised the proposal of ''nihonium'' that June,
and set a five-month term to collect comments, after which the name would be formally established at a conference.
The name was officially approved on 28 November 2016.
The naming ceremony for the new element was held in
Tokyo
Tokyo, officially the Tokyo Metropolis, is the capital of Japan, capital and List of cities in Japan, most populous city in Japan. With a population of over 14 million in the city proper in 2023, it is List of largest cities, one of the most ...
, Japan, on 14 March 2017, with
Naruhito
Naruhito (born 23 February 1960) is Emperor of Japan. He acceded to the Chrysanthemum Throne following 2019 Japanese imperial transition, the abdication of his father, Akihito, on 1 May 2019, beginning the Reiwa era. He is the 126th monarch, ...
, then the Crown Prince of Japan, in attendance.
Isotopes
Nihonium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesised in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Eight different isotopes of nihonium have been reported with atomic masses 278, 282–287, and 290 (
287Nh and
290Nh are unconfirmed); they all decay through alpha decay to isotopes of
roentgenium.
There have been indications that nihonium-284 can also decay by
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...
to
copernicium
Copernicium is a synthetic chemical element; it has 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 ap ...
-284, though estimates of the
partial half-life
Partial may refer to:
Mathematics
* Partial derivative, derivative with respect to one of several variables of a function, with the other variables held constant
** ∂, a symbol that can denote a partial derivative, sometimes pronounced "partial ...
for this branch vary strongly by model. A
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
branch of nihonium-285 has also been reported.
[
]
Stability and half-lives
The stability of nuclei quickly decreases with the increase in atomic number after curium
Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inten ...
, element 96, whose half-life is over ten thousand times longer than that of any subsequent element. All isotopes with an atomic number above 101 undergo radioactive decay with half-lives of less than 30 hours: this is because of the ever-increasing Coulomb repulsion
Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called the ''electrostatic f ...
of protons, so that the strong nuclear force
In nuclear physics and particle physics, the strong interaction, also called the strong force or strong nuclear force, is one of the four known fundamental interactions. It confines quarks into protons, neutrons, and other hadron particles, an ...
cannot hold the nucleus together against spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...
for long. Calculations suggest that in the absence of other stabilising factors, elements with more than 103 protons should not exist. Researchers in the 1960s suggested that the closed nuclear shells around 114 protons and 184 neutrons should counteract this instability, and create an "island of stability
In nuclear physics, the island of stability is a predicted set of isotopes of superheavy elements that may have considerably longer half-lives than known isotopes of these elements. It is predicted to appear as an "island" in the chart of nuclid ...
" containing nuclides with half-lives reaching thousands or millions of years. The existence of the island is still unproven, but the existence of the superheavy element
Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...
s (including nihonium) confirms that the stabilising effect is real, and in general the known superheavy nuclides become longer-lived as they approach the predicted location of the island.
All nihonium isotopes are unstable and radioactive; the heavier nihonium isotopes are more stable than the lighter ones, as they are closer to the centre of the island. The most stable known nihonium isotope, 286Nh, is also the heaviest; it has a half-life of 8 seconds. The isotope 285Nh, as well as the unconfirmed 287Nh and 290Nh, have also been reported to have half-lives of over a second. The isotopes 284Nh and 283Nh have half-lives of 0.90 and 0.12 seconds respectively. The remaining two isotopes have half-lives between 0.1 and 100 milliseconds: 282Nh has a half-life of 61 milliseconds, and 278Nh, the lightest known nihonium isotope, is also the shortest-lived, with a half-life of 2.0 milliseconds. This rapid increase in the half-lives near the closed neutron shell at ''N'' = 184 is seen in roentgenium, copernicium, and nihonium (elements 111 through 113), where each extra neutron so far multiplies the half-life by a factor of 5 to 20.
The unknown isotopes in the gap between 278Nh and 282Nh are too heavy to be produced by cold fusion and too light to be produced by hot fusion. The missing 280Nh and 281Nh may be populated as daughters of 284Mc and 285Mc, producible in the 241Am+48Ca reaction, but this has not yet been attempted. Of particular interest is 281Nh, as it is the expected great-granddaughter of 293 119, a possible product of the 243Am+54Cr reaction. Production of 282Mc and 283Mc is possible in the 243Am+44Ca reaction (though it has a lower cross-section), and their daughters would be 278Nh (known) and 279Nh. The heavier isotopes 287Nh through 290Nh might be synthesised using charged-particle evaporation, using the 242Pu+48Ca and 244Pu+48Ca reactions where one proton and some neutrons are evaporated.
Predicted properties
Very few properties of nihonium or its compounds have been measured; this is due to its extremely limited and expensive production and the fact it decays very quickly. Properties of nihonium mostly remain unknown and only predictions are available.
Physical and atomic
Nihonium is the first member of the 7p series of elements and the heaviest group 13 element on the periodic table, below boron
Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...
, aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
, gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, indium
Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
, and thallium
Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...
. All the group 13 elements except boron are metals, and nihonium is expected to follow suit. Nihonium is predicted to show many differences from its lighter homologues. The major reason for this is the spin–orbit (SO) interaction, which is especially strong for the superheavy element
Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...
s, because their electrons move much faster than in lighter atoms, at velocities close to the speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...
. In relation to nihonium atoms, it lowers the 7s and the 7p electron energy levels (stabilising those electrons), but two of the 7p electron energy levels are stabilised more than the other four. The stabilisation of the 7s electrons is called 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 o ...
, and the separation of the 7p subshell into the more and less stabilised parts is called subshell splitting. Computational chemists see the split as a change of the second, azimuthal quantum number
In quantum mechanics, the azimuthal quantum number is a quantum number for an atomic orbital that determines its angular momentum operator, orbital angular momentum and describes aspects of the angular shape of the orbital. The azimuthal quantum ...
''l'', from 1 to 1/2 and 3/2 for the more and less stabilised parts of the 7p subshell, respectively. The quantum number corresponds to the letter in the electron orbital name: 0 to s, 1 to p, 2 to d, etc. For theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s2 7p1/21. The first ionisation energy of nihonium is expected to be 7.306 eV, the highest among the metals of group 13. Similar subshell splitting should exist for the 6d electron levels, with four being 6d3/2 and six being 6d5/2. Both these levels are raised to be close in energy to the 7s ones, high enough to possibly be chemically active. This would allow for the possibility of exotic nihonium compounds without lighter group 13 analogues.
Periodic trends would predict nihonium to have an atomic radius larger than that of thallium due to it being one period further down the periodic table, but calculations suggest nihonium has an atomic radius of about 170 pm, the same as that of thallium, due to the relativistic stabilisation and contraction of its 7s and 7p1/2 orbitals. Thus, nihonium is expected to be much denser than thallium, with a predicted density of about 16 to 18 g/cm3 compared to thallium's 11.85 g/cm3, since nihonium atoms are heavier than thallium atoms but have the same volume. Bulk nihonium is expected to have a hexagonal close-packed
In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement (or Lattice (group), lattice). Carl Friedrich Gauss proved that the highest average density – that is, the greatest fract ...
crystal structure, like thallium. The melting and boiling points of nihonium have been predicted to be 430 °C and 1100 °C respectively, exceeding the values for indium and thallium, following periodic trends. Nihonium should have a bulk modulus
The bulk modulus (K or B or k) of a substance is a measure of the resistance of a substance to bulk compression. It is defined as the ratio of the infinitesimal pressure increase to the resulting ''relative'' decrease of the volume.
Other mo ...
of 20.8 GPa, about half that of thallium (43 GPa).
Chemical
The chemistry of nihonium is expected to be very different from that of thallium. This difference stems from the spin–orbit splitting of the 7p shell, which results in nihonium being between two relatively inert closed-shell elements (copernicium
Copernicium is a synthetic chemical element; it has 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 ap ...
and flerovium). Nihonium is expected to be less reactive than thallium, because of the greater stabilisation and resultant chemical inactivity of the 7s subshell in nihonium compared to the 6s subshell in thallium. The standard electrode potential
In electrochemistry, standard electrode potential E^\ominus, or E^\ominus_, is the electrode potential (a measure of the reducing power of any element or compound) which the IUPAC "Gold Book" defines as ''"the value of the standard emf ( electrom ...
for the Nh+/Nh couple is predicted to be 0.6 V. Nihonium should be a rather noble metal
A noble metal is ordinarily regarded as a metallic chemical element, element that is generally resistant to corrosion and is usually found in nature in its native element, raw form. Gold, platinum, and the other platinum group metals (ruthenium ...
.
The metallic group 13 elements are typically found in two oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
s: +1 and +3. The former results from the involvement of only the single p electron in bonding, and the latter results in the involvement of all three valence electrons, two in the s-subshell and one in the p-subshell. Going down the group, bond energies decrease and the +3 state becomes less stable, as the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the s-electrons. Hence, for aluminium and gallium +3 is the most stable state, but +1 gains importance for indium and by thallium it becomes more stable than the +3 state. Nihonium is expected to continue this trend and have +1 as its most stable oxidation state.
The simplest possible nihonium compound is the monohydride, NhH. The bonding is provided by the 7p1/2 electron of nihonium and the 1s electron of hydrogen. The SO interaction causes the 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 ...
of nihonium monohydride to be reduced by about 1 eV and the nihonium–hydrogen bond length to decrease as the bonding 7p1/2 orbital is relativistically contracted. This is unique among the 7p element monohydrides; all the others have relativistic expansion of the bond length instead of contraction. Another effect of the SO interaction is that the Nh–H bond is expected to have significant pi bond
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbital ...
ing character (side-on orbital overlap), unlike the almost pure sigma bond
In chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalent chemical bond. They are formed by head-on overlapping between atomic orbitals along the internuclear axis. Sigma bonding is most simply defined for diat ...
ing (head-on orbital overlap) in thallium monohydride (TlH). The analogous monofluoride (Nh F) should also exist. Nihonium(I) is predicted to be more similar to silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
(I) than thallium(I): the Nh+ ion is expected to more willingly bind anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s, so that NhCl should be quite soluble in excess hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
or ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
; TlCl is not. In contrast to Tl+, which forms the strongly basic
Basic or BASIC may refer to:
Science and technology
* BASIC, a computer programming language
* Basic (chemistry), having the properties of a base
* Basic access authentication, in HTTP
Entertainment
* Basic (film), ''Basic'' (film), a 2003 film
...
hydroxide ( TlOH) in solution, the Nh+ cation should instead hydrolyse all the way to the amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
Etymology and terminology
Amphoteric is d ...
oxide Nh2O, which would be soluble in aqueous ammonia and weakly soluble in water.
The adsorption
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...
behaviour of nihonium on gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
surfaces in thermochromatographical experiments is expected to be closer to that of astatine
Astatine is a chemical element; it has Symbol (chemistry), symbol At and atomic number 85. It is the abundance of elements in Earth's crust, rarest naturally occurring element in the Earth's crust, occurring only as the Decay chain, decay product ...
than that of thallium. The destabilisation of the 7p3/2 subshell effectively leads to a valence shell closing at the 7s2 7p2 configuration rather than the expected 7s2 7p6 configuration with its stable octet. As such, nihonium, like astatine, can be considered to be one p-electron short of a closed valence shell. Hence, even though nihonium is in group 13, it has several properties similar to the group 17 elements. (Tennessine
Tennessine is a synthetic element; it has Chemical symbol, symbol Ts and atomic number 117. It has the second-highest atomic number and joint-highest atomic mass of all known elements and is the penultimate element of the Period 7 element, 7th ...
in group 17 has some group-13-like properties, as it has three valence electrons outside the 7s2 7p2 closed shell.) Nihonium is expected to be able to gain an electron to attain this closed-shell configuration, forming the −1 oxidation state like the halogens (fluorine, chlorine, bromine, iodine, and astatine). This state should be more stable than it is for thallium as the SO splitting of the 7p subshell is greater than that for the 6p subshell. Nihonium should be the most electronegativity, electronegative of the metallic group 13 elements, even more electronegative than tennessine, the period 7 congener of the halogens: in the compound NhTs, the negative charge is expected to be on the nihonium atom rather than the tennessine atom. The −1 oxidation should be more stable for nihonium than for tennessine. The electron affinity of nihonium is calculated to be around 0.68 eV, higher than thallium's at 0.4 eV; tennessine's is expected to be 1.8 eV, the lowest in its group. It is theoretically predicted that nihonium should have an enthalpy of sublimation around 150 kJ/mol and an enthalpy of adsorption on a gold surface around −159 kJ/mol.
Significant 6d involvement is expected in the Nh–Au bond, although it is expected to be more unstable than the Tl–Au bond and entirely due to magnetic interactions. This raises the possibility of some transition metal character for nihonium. On the basis of the small energy gap between the 6d and 7s electrons, the higher oxidation states +3 and +5 have been suggested for nihonium. Some simple compounds with nihonium in the +3 oxidation state would be the trihydride (NhH3), trifluoride (NhF3), and trichloride (Nhchlorine, Cl3). These molecules are predicted to be T-shaped molecular geometry, T-shaped and not trigonal planar molecular geometry, trigonal planar as their boron
Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...
analogues are: this is due to the influence of the 6d5/2 electrons on the bonding. The heavier nihonium tribromide (Nhbromine, Br3) and triiodide (Nhiodine, I3) are trigonal planar due to the increased steric repulsion between the peripheral atoms; accordingly, they do not show significant 6d involvement in their bonding, though the large 7s–7p energy gap means that they show reduced sp2 hybridisation compared to their boron analogues.
The bonding in the lighter NhX3 molecules can be considered as that of a linear species (similar to mercury(II) fluoride, HgF2 or ) with an additional Nh–X bond involving the 7p orbital of nihonium perpendicular to the other two ligands. These compounds are all expected to be highly unstable towards the loss of an X2 molecule and reduction to nihonium(I):
:NhX3 → NhX + X2
Nihonium thus continues the trend down group 13 of reduced stability of the +3 oxidation state, as all five of these compounds have lower reaction energies than the unknown thallium(III) iodide. The +3 state is stabilised for thallium in anionic complexes such as , and the presence of a possible vacant coordination site on the lighter T-shaped nihonium trihalides is expected to allow a similar stabilisation of and perhaps .
The +5 oxidation state is unknown for all lighter group 13 elements: calculations predict that nihonium pentahydride (NhH5) and pentafluoride (NhF5) should have a square pyramidal molecular geometry, but also that both would be highly thermodynamically unstable to loss of an X2 molecule and reduction to nihonium(III). Again, some stabilisation is expected for anionic complexes, such as . The structures of the nihonium trifluoride and pentafluoride molecules are the same as those for chlorine trifluoride and chlorine pentafluoride, pentafluoride.
Experimental chemistry
The isotopes 284Nh, 285Nh, and 286Nh have half-lives long enough for chemical investigation. From 2010 to 2012, some preliminary chemical experiments were performed at the JINR to determine the volatility (chemistry), volatility of nihonium. The isotope 284Nh was investigated, made as the daughter of 288Mc produced in the 243Am+48Ca reaction. The nihonium atoms were synthesised in a recoil chamber and then carried along polytetrafluoroethylene (PTFE) capillaries at 70 °C by a carrier gas to the gold-covered detectors. About ten to twenty atoms of 284Nh were produced, but none of these atoms were registered by the detectors, suggesting either that nihonium was similar in volatility to the noble gases (and thus diffused away too quickly to be detected) or, more plausibly, that pure nihonium was not very volatile and thus could not efficiently pass through the PTFE capillaries. Formation of the hydroxide NhOH should ease the transport, as nihonium hydroxide is expected to be more volatile than elemental nihonium, and this reaction could be facilitated by adding more water vapour into the carrier gas. It seems likely that this formation is not kinetically favoured, so the longer-lived isotopes 285Nh and 286Nh were considered more desirable for future experiments.
A 2017 experiment at the JINR, producing 284Nh and 285Nh via the 243Am+48Ca reaction as the daughters of 288Mc and 289Mc, avoided this problem by removing the quartz surface, using only PTFE. No nihonium atoms were observed after chemical separation, implying an unexpectedly large retention of nihonium atoms on PTFE surfaces. This experimental result for the interaction limit of nihonium atoms with a PTFE surface disagrees significantly with previous theory, which expected a lower value of 14.00 kJ/mol. This suggests that the nihonium species involved in the previous experiment was likely not elemental nihonium but rather nihonium hydroxide, and that high-temperature techniques such as vacuum chromatography would be necessary to further probe the behaviour of elemental nihonium. Bromine saturated with boron tribromide has been suggested as a carrier gas for experiments on nihonium chemistry; this oxidises nihonium's lighter congener thallium to thallium(III), providing an avenue to investigate the oxidation states of nihonium, similar to earlier experiments done on the bromides of group 5 elements, including the superheavy dubnium
Dubnium is a synthetic element, synthetic chemical element; it has Chemical symbol, 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 hours. ...
.
A 2024 experiment at the GSI, producing 284Nh via the 243Am+48Ca reaction as daughter of 288Mc, studied the adsorption of nihonium and moscovium on SiO2 and gold surfaces. The adsorption enthalpy of nihonium on SiO2 was determined experimentally as (68% confidence interval). Nihonium was determined to be less reactive with the SiO2 surface than its lighter congener thallium, but more reactive than its closed-shell neighbours copernicium and flerovium. This arises because of the relativistic stabilisation of the 7p1/2 shell.
Notes
References
Bibliography
*
*
*
*
*
External links
Nihonium
at ''The Periodic Table of Videos'' (University of Nottingham)
Uut and Uup Add Their Atomic Mass to Periodic Table
Superheavy elements
WebElements.com: Nihonium
{{Authority control
Nihonium,
Chemical elements
Chemical_elements_with_hexagonal_close-packed_structure
Synthetic elements