Community hub
0 subscribers7 pages, 0 posts
Recent from talks
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Be the first to start a discussion here.
Contribute something
Welcome to the community hub built to collect knowledge and have discussions related to Transuranium element.
Nothing was collected or created yet.
Transuranium element
View on Wikipediafrom Wikipedia
The transuranium (or transuranic) elements are the chemical elements with atomic number greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. They are synthetic and none occur naturally on Earth, except for neptunium and plutonium which have been found in trace amounts in nature.
Overview
[edit]
Of the elements with atomic numbers 1 to 92, most can be found in nature, having stable isotopes (such as lead) or very long-lived radioisotopes (such as uranium), or existing as common decay products of the decay of uranium and thorium (such as radium). The exceptions are technetium, promethium, astatine, and francium; all four occur in nature, but only in very minor branches of the uranium and thorium decay chains, and thus all except francium were first discovered by synthesis in the laboratory rather than in nature.
All elements with higher atomic numbers have been first discovered in the laboratory, with neptunium and plutonium (the first two of these) later discovered in nature. They are all radioactive, with a half-life much shorter than the age of the Earth, so any primordial (i.e. present at the Earth's formation) atoms of these elements, have long since decayed. Trace amounts of neptunium and plutonium form in some uranium-rich rock, and small amounts are produced during atmospheric tests of nuclear weapons. These two elements are generated by neutron capture in uranium ore with subsequent beta decays (e.g. 238U + n → 239U → 239Np → 239Pu).
All elements beyond plutonium are entirely synthetic, at least on Earth;[1][2] they are created in nuclear reactors or particle accelerators. The half-lives of these elements show a general trend of decreasing as atomic numbers increase. There are exceptions, however, including several isotopes of curium and dubnium. Some heavier elements in this series, around atomic numbers 110–114, are thought to break the trend and demonstrate increased nuclear stability, comprising the theoretical island of stability.[3]
Transuranic elements are difficult and expensive to produce, and their prices increase rapidly with atomic number. As of 2008, the cost of weapons-grade plutonium was around $4,000/gram,[4] and californium exceeded $60,000,000/gram.[5] Einsteinium is the heaviest element that has been produced in macroscopic quantities.[6]
Transuranic elements that have not been discovered, or have been discovered but are not yet officially named, use IUPAC's systematic element names. The naming of transuranic elements may be a source of controversy.
Discoveries
[edit]So far, essentially all transuranium elements have been discovered at four laboratories: Lawrence Berkeley National Laboratory (LBNL) in the United States (elements 93–101, 106, and joint credit for 103–105), the GSI Helmholtz Centre for Heavy Ion Research in Germany (elements 107–112), RIKEN in Japan (element 113), and the Joint Institute for Nuclear Research (JINR) in Russia (elements 102 and 114–118, and joint credit for 103–105).
- The Radiation Laboratory (now LBNL) at University of California, Berkeley, led principally by Edwin McMillan, Glenn Seaborg, and Albert Ghiorso, during 1945–1974:
- 93. neptunium, Np, named after the planet Neptune, as it follows uranium and Neptune follows Uranus in the planetary sequence (1940).
- 94. plutonium, Pu, named after Pluto,[a] following the same naming rule as it follows neptunium and Pluto follows Neptune in the Solar System (1940).
- 95. americium, Am, named because it is an analog to europium, and so was named after the continent where it was first produced (1944).
- 96. curium, Cm, named after Pierre and Marie Curie, scientists who separated out the first radioactive elements (1944), as its lighter analog gadolinium was named after Johan Gadolin.
- 97. berkelium, Bk, named after Lawrence Berkeley National Laboratory, where it was first synthesized (1949).
- 98. californium, Cf, named after California, where LBNL is located (1950).
- 99. einsteinium, Es, named after Albert Einstein (1952).
- 100. fermium, Fm, named after Enrico Fermi, the physicist who produced the first controlled chain reaction (1952).
- 101. mendelevium, Md, named after Russian chemist Dmitri Mendeleev, credited for being the primary creator of the periodic table of the chemical elements (1955).
- 102. nobelium, No, named after Alfred Nobel (1958). The element was originally claimed by a team at the Nobel Institute in Sweden (1957) – though it later became apparent that the Swedish team had not discovered the element, the LBNL team decided to adopt their name nobelium. This discovery was also claimed by JINR, which doubted the LBNL claim, and named the element joliotium (Jl) after Frédéric Joliot-Curie (1965). IUPAC concluded that the JINR had been the first to convincingly synthesize the element (1965), but retained the name nobelium as deeply entrenched in the literature.
- 103. lawrencium, Lr, named after Ernest Lawrence, a physicist best known for development of the cyclotron, and the person for whom Lawrence Livermore National Laboratory and LBNL (which hosted the creation of these transuranium elements) are named (1961). This discovery was also claimed by the JINR (1965), which doubted the LBNL claim and proposed the name rutherfordium (Rf) after Ernest Rutherford. IUPAC concluded that credit should be shared, retaining the name lawrencium as entrenched in the literature.
- 104. rutherfordium, Rf, named after Ernest Rutherford, who was responsible for the concept of the atomic nucleus (1969). This discovery was also claimed by JINR, led principally by Georgy Flyorov: they named the element kurchatovium (Ku), after Igor Kurchatov. IUPAC concluded that credit should be shared, and adopted the LBNL name rutherfordium.
- 105. dubnium, Db, an element that is named after Dubna, where JINR is located. Originally named hahnium (Ha) in honor of Otto Hahn by the Berkeley group (1970). This discovery was also claimed by JINR, which named it nielsbohrium (Ns) after Niels Bohr. IUPAC concluded that credit should be shared, and renamed the element dubnium to honour the JINR team.
- 106. seaborgium, Sg, named after Glenn T. Seaborg. This name caused controversy because Seaborg was still alive, but it eventually became accepted by international chemists (1974). This discovery was also claimed by JINR. IUPAC concluded that the Berkeley team had been the first to convincingly synthesize the element.
- The Gesellschaft für Schwerionenforschung (Society for Heavy Ion Research) in Darmstadt, Hessen, Germany, led principally by Gottfried Münzenberg, Peter Armbruster, and Sigurd Hofmann, during 1980–2000:
- 107. bohrium, Bh, named after Danish physicist Niels Bohr, important in the elucidation of the structure of the atom (1981). This discovery was also claimed by JINR. IUPAC concluded that the GSI had been the first to convincingly synthesise the element. The GSI team had originally proposed nielsbohrium (Ns) to resolve the naming dispute on element 105, but this was changed by IUPAC as there was no precedent for using a scientist's first name in an element name.
- 108. hassium, Hs, named after the Latin form of the name of Hessen, the German Bundesland where this work was performed (1984). This discovery was also claimed by JINR. IUPAC concluded that the GSI had been the first to convincingly synthesize the element, while acknowledging the pioneering work at JINR.
- 109. meitnerium, Mt, named after Lise Meitner, an Austrian physicist who was one of the earliest scientists to study nuclear fission (1982).
- 110. darmstadtium, Ds, named after Darmstadt, Germany, the city in which this work was performed (1994). This discovery was also claimed by JINR, which proposed the name becquerelium after Henri Becquerel, and by LBNL, which proposed the name hahnium to resolve the dispute on element 105 (despite having protested the reusing of established names for different elements). IUPAC concluded that GSI had been the first to convincingly synthesize the element.
- 111. roentgenium, Rg, named after Wilhelm Röntgen, discoverer of X-rays (1994).
- 112. copernicium, Cn, named after astronomer Nicolaus Copernicus (1996).
- RIKEN in Wakō, Saitama, Japan, led principally by Kōsuke Morita:
- JINR in Dubna, Russia, led principally by Yuri Oganessian, in collaboration with several other labs including Lawrence Livermore National Laboratory (LLNL), since 2000:
- 114. flerovium, Fl, named after the Flerov Laboratory of Nuclear Reactions in JINR (1999).
- 115. moscovium, Mc, named after Moscow Oblast, where the element was discovered (2004).
- 116. livermorium, Lv, named after Lawrence Livermore National Laboratory, a collaborator with JINR in the discovery (2000).
- 117. tennessine, Ts, after Tennessee, the location of Oak Ridge National Laboratory (2010).
- 118. oganesson, Og, after Yuri Oganessian, who led the JINR team in its discovery of elements 114 to 118 (2002).
Superheavy elements
[edit]Superheavy elements, (also known as superheavies, or superheavy atoms, commonly abbreviated SHE) usually refer to the transactinide elements beginning with rutherfordium (atomic number 104). (Lawrencium, the first 6d element, is sometimes but not always included as well.) They have only been made artificially and currently serve no practical purpose because their short half-lives cause them to decay after a very short time, ranging from a few hours to just milliseconds, which also makes them extremely hard to study.[7][8]
Superheavies have all been created since the latter half of the 20th century and are continually being created during the 21st century as technology advances. They are created through the bombardment of elements in a particle accelerator, in quantities on the atomic scale, and no method of mass creation has been found.[7]
Applications
[edit]Transuranic elements may be used to synthesize superheavy elements.[9] Elements of the island of stability have potentially important military applications, including the development of compact nuclear weapons.[10] The potential everyday applications are vast; americium is used in devices such as smoke detectors and spectrometers.[11][12]
See also
[edit]- Bose–Einstein condensate (also known as superatom)
- Minor actinide
- Deep geological repository, a place to deposit transuranic waste
References
[edit]- ^ Pluto was a planet at the time of naming, but has since been reclassified as a dwarf planet.
- ^ Cowan, John J.; et al. (January 2021). "Origin of the heaviest elements: The rapid neutron-capture process". Reviews of Modern Physics. 93 (1) 015002. arXiv:1901.01410. Bibcode:2021RvMP...93a5002C. doi:10.1103/RevModPhys.93.015002.
- ^ Gopka, Vera F.; et al. (December 2004). Zverko, J.; et al. (eds.). On the radioactive shells in peculiar main sequence stars: the phenomenon of Przybylski's star. The A-Star Puzzle, held in Poprad, Slovakia, July 8-13, 2004. IAU Symposium, No. 224. Cambridge, UK: Cambridge University Press. pp. 734–742. Bibcode:2004IAUS..224..734G. doi:10.1017/S174392130500966X.
- ^ Considine, Glenn, ed. (2002). Van Nostrand's Scientific Encyclopedia (9th ed.). New York: Wiley Interscience. p. 738. ISBN 978-0-471-33230-5.
- ^ Morel, Andrew (2008). Elert, Glenn (ed.). "Price of Plutonium". The Physics Factbook. Archived from the original on 20 October 2018.
- ^ Martin, Rodger C.; Kos, Steve E. (2001). Applications and Availability of Californium-252 Neutron Sources for Waste Characterization (Report). CiteSeerX 10.1.1.499.1273.
- ^ Silva, Robert J. (2006). "Fermium, Mendelevium, Nobelium and Lawrencium". In Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (Third ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 978-1-4020-3555-5.
- ^ a b Heenen, Paul-Henri; Nazarewicz, Witold (2002). "Quest for superheavy nuclei" (PDF). Europhysics News. 33 (1): 5–9. Bibcode:2002ENews..33....5H. doi:10.1051/epn:2002102. Archived (PDF) from the original on 20 July 2018.
- ^ Greenwood, Norman N. (1997). "Recent developments concerning the discovery of elements 100–111" (PDF). Pure and Applied Chemistry. 69 (1): 179–184. doi:10.1351/pac199769010179. S2CID 98322292. Archived (PDF) from the original on 21 July 2018.
- ^ Lougheed, R. W.; et al. (1985). "Search for superheavy elements using 48Ca + 254Esg reaction". Physical Review C. 32 (5): 1760–1763. Bibcode:1985PhRvC..32.1760L. doi:10.1103/PhysRevC.32.1760. PMID 9953034.
- ^ Gsponer, André; Hurni, Jean-Pierre (1997). The Physical Principles of Thermonuclear Explosives, Intertial Confinement Fusion, and the Quest for Fourth Generation Nuclear Weapons (PDF). International Network of Engineers and Scientists Against Proliferation. pp. 110–115. ISBN 978-3-933071-02-6. Archived (PDF) from the original on 6 June 2018.
- ^ "Smoke Detectors and Americium", Nuclear Issues Briefing Paper, vol. 35, May 2002, archived from the original on 11 September 2002, retrieved 2015-08-26
- ^ Nuclear Data Viewer 2.4, NNDC
Further reading
[edit]- Eric Scerri, A Very Short Introduction to the Periodic Table, Oxford University Press, Oxford, 2011.
- The Superheavy Elements
- Annotated bibliography for the transuranic elements from the Alsos Digital Library for Nuclear Issues.
- Transuranium elements
- Super Heavy Elements network official website (network of the European integrated infrastructure initiative EURONS)
- Darmstadtium and beyond
- Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: Traces of transuranium elements in terrestrial minerals? (Online, PDF-Datei, 493 kB)
- Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: The search for super heavy elements (SHE) in terrestrial minerals using XRF with high energy synchrotron radiation. (Online, PDF-Datei, 446 kB)
| International | |
|---|---|
| National | |
| Other | |
Transuranium element
View on Grokipediafrom Grokipedia
Transuranium elements, also known as transuranic elements, are the chemical elements in the periodic table with atomic numbers greater than 92, the atomic number of uranium; all such elements are synthetic, radioactive, and lack stable isotopes.[1] They belong to the actinide series from neptunium (atomic number 93) to lawrencium (103), with subsequent superheavy elements extending beyond, and are produced artificially through nuclear reactions in reactors, particle accelerators, or nuclear explosions. Since then, superheavy elements up to oganesson (118) have been synthesized, bringing the total to 26 transuranium elements as of 2025.[2] These elements emit alpha particles with energies typically ranging from 5 to 8 MeV or higher, and their isotopes exhibit half-lives varying widely from seconds to millions of years, such as 2.1 × 10⁶ years for neptunium-237 and 24,400 years for plutonium-239.[1]
The discovery of transuranium elements began during World War II research on nuclear fission, with neptunium (element 93) identified in 1940 by Edwin M. McMillan and Philip H. Abelson at the University of California, Berkeley, through the bombardment of uranium-238 with neutrons in a cyclotron, followed by chemical separation revealing a new activity.[3] Plutonium (element 94) was synthesized shortly after in December 1940 by McMillan, Glenn T. Seaborg, Joseph W. Kennedy, and Arthur C. Wahl, via deuteron bombardment of uranium, with its chemical properties confirmed in early 1941, marking the first fissile material beyond uranium suitable for nuclear chain reactions.[4] Subsequent elements, including americium (95) in 1944 and curium (96) in 1944, were discovered by Seaborg and collaborators at Berkeley using similar accelerator-based methods and ion-exchange chemistry, leading to the identification of ten transuranium elements by the mid-20th century, from neptunium to lawrencium (103) in 1961.[3] These discoveries, driven by the Manhattan Project, reshaped the periodic table by establishing the actinide concept, where 5f electrons fill orbitals analogous to the 4f lanthanides, influencing their chemical behavior to resemble rare earths rather than transition metals.[3]
Transuranium elements exhibit complex chemical properties, often forming compounds in oxidation states from +3 to +6, with plutonium notable for its six accessible states and silvery-white metallic appearance that tarnishes in air due to oxide formation.[4] They are highly radioactive, concentrating in biological systems like bone and liver upon internal exposure, posing significant health risks from alpha radiation, which has high linear energy transfer and can cause osteosarcoma or lung cancer.[1] Despite these hazards, practical applications include plutonium-239 as fissile material in nuclear reactors and weapons, plutonium-238 in radioisotope thermoelectric generators for space missions like Voyager probes, and americium-241 in ionization smoke detectors.[1] Ongoing research into transuranium elements includes their production for fundamental studies, as well as applications in nuclear waste management and advanced fuels, though scarcity and short half-lives of heavier isotopes limit widespread use.
Radioactivity in transuranium elements primarily proceeds through alpha decay, where the nucleus emits an alpha particle (helium-4 nucleus), reducing the atomic number by 2 and mass by 4. This mode dominates for many isotopes, such as neptunium-237 (alpha decay to protactinium-233) and plutonium-244 (alpha decay to uranium-240 with a branching ratio of 99.88%). Spontaneous fission, in which the nucleus splits into two lighter fragments, becomes significant for heavier isotopes like plutonium-244 (branching ratio of 0.12%) and is more prevalent in elements beyond curium, contributing to neutron emission and shorter half-lives. Electron capture, where a proton captures an inner-shell electron to form a neutron, occurs in lighter transuranium isotopes with atomic numbers near 93, such as neptunium-236 decaying to plutonium-236. Beta-minus decay is also observed in neutron-rich isotopes, converting a neutron to a proton. These decay modes often compete, with branching ratios varying by isotope; for example, curium-247 primarily undergoes alpha decay to americium-243.[62][66][67][20]
Densities of transuranium elements are generally high, reflecting their compact atomic structures, but show a decreasing trend across the series due to actinide contraction, where f-orbital filling leads to poorer shielding and contracted atomic radii. Neptunium metal has a density of 20.45 g/cm³ in its alpha phase at room temperature. Plutonium's alpha phase density is 19.86 g/cm³, while curium's density is lower at 13.51 g/cm³, attributed to the increasing influence of lanthanide-like contraction in later actinides. Melting points vary irregularly but are typically elevated, indicative of strong metallic bonding; neptunium melts at 644 °C, plutonium at 640 °C, and curium at 1340 °C, with the rise for curium linked to enhanced directional bonding from f-electron participation.[62][20][68]
In superheavy elements (atomic numbers >103), relativistic effects profoundly alter physical properties due to inner electrons approaching speeds near the speed of light (about 0.99c for Z=118). These effects cause contraction of s and p_{1/2} orbitals and expansion of d and p_{3/2} orbitals, resulting in smaller overall atomic sizes than non-relativistic predictions and influencing metallic radii and bonding. For oganesson, this leads to a predicted electron configuration of [Rn] 5f^{14} 6d^{10} 7s^2 7p^4 (with relativistic stabilization of 7s), deviating from lighter p-block trends and potentially yielding noble-gas-like properties with reduced atomic volume. Such effects intensify with atomic number, scaling roughly as Z^2, and are essential for accurate modeling of superheavy isotopes' stability and sizes.[69][70][64]
Definition and Classification
Definition
Transuranium elements, also referred to as transuranic elements, are the chemical elements in the periodic table with atomic numbers greater than 92, the atomic number of uranium. This category encompasses all elements starting from neptunium (atomic number 93) through the actinides up to lawrencium (103), the transactinides from rutherfordium (104) to oganesson (118), and theoretically beyond into undiscovered higher elements.[5][6][1] These elements are predominantly synthetic, having been created through artificial nuclear reactions in laboratories and particle accelerators, with no stable isotopes occurring naturally in significant quantities. Trace amounts of neptunium and plutonium, however, are found in nature as byproducts of neutron capture by uranium in ores, followed by beta decay processes.[7][5] The nomenclature for transuranium elements is governed by the International Union of Pure and Applied Chemistry (IUPAC), which assigns temporary systematic names to newly synthesized elements based on their atomic number until official names are approved. For instance, element 112 was initially designated ununbium (Uub), derived from Latin roots for its atomic number (one-one-two), before receiving the permanent name copernicium (Cn) in 2010.[8][9] In the periodic table, transuranium elements extend the actinide series beyond uranium, filling the 5f orbital block from neptunium to lawrencium, and continuing into the 6d and 7p blocks for transactinides, with predictions of a superactinide series beginning around element 122 that would involve 5g, 6f, and 7d orbitals.[1][9]Actinides and Superheavy Elements
Transuranium elements are classified into the actinide series and superheavy elements, with the actinides encompassing atomic numbers 93 through 103, from neptunium to lawrencium.[6] These elements occupy the f-block of the periodic table, where the filling of 5f orbitals dominates their electronic structure, leading to complex chemistry influenced by variable oxidation states and strong metal-ligand interactions.[10] Relativistic effects become increasingly significant in this series due to the high nuclear charge, causing orbital contraction and stabilization of higher oxidation states, which alters bonding properties compared to lighter f-block elements.[11] Superheavy elements begin at atomic number 104 and extend through 118, often termed transactinides, and are positioned in the 6d transition metal series (elements 104–112) and the 7p main group series (elements 113–118).[12] The named elements in this range include rutherfordium (104), dubnium (105), seaborgium (106), bohrium (107), hassium (108), meitnerium (109), darmstadtium (110), roentgenium (111), copernicium (112), nihonium (113), flerovium (114), moscovium (115), livermorium (116), tennessine (117), and oganesson (118), as officially recognized by IUPAC.[13] These elements exhibit pronounced relativistic effects that destabilize the periodic trends observed in lighter homologues, resulting in unexpected electronic configurations and chemical behaviors.[14] Theoretical extensions of the periodic table predict superactinides from atomic numbers 122 to 153 (and potentially up to 157), proposed by Glenn Seaborg as part of a g-block series following the actinides.[15] In models of the island of stability, these elements are anticipated to occupy positions where closed nuclear shells could enhance stability, particularly around doubly magic configurations near Z=120–126 and N=184, though synthesis remains beyond current capabilities. As of 2025, experiments at facilities like GSI/FAIR have begun to map the shoreline of the island of stability through observations of increasing half-lives in superheavy nuclei, including the synthesis of the new isotope seaborgium-257 and proposed fusion reactions using titanium-50 beams on plutonium targets to approach element 120.[16][17][18][19] Among transuranium elements, plutonium (atomic number 94) stands out as the most stable, with its isotope plutonium-244 possessing a half-life of approximately 80 million years, allowing trace natural occurrence and practical applications.[20] At the opposite end, oganesson (118) deviates from noble gas expectations due to intense relativistic effects, which destabilize its closed-shell configuration and confer halogen-like reactivity, potentially enabling compound formation despite its group 18 placement.[21]History of Discovery
Early Syntheses
The first transuranium element, neptunium (atomic number 93), was synthesized in 1940 by Edwin M. McMillan and Philip H. Abelson at the University of California, Berkeley.[22] They achieved this by irradiating uranium with neutrons produced in a cyclotron, leading to the formation of uranium-239, which has a half-life of approximately 23 minutes and decays via beta emission to neptunium-239. The identification relied on chemical separation techniques to isolate the new element from uranium, confirmed through measurements of its beta particle emissions.[22] Building on this work, plutonium (atomic number 94) was discovered in early 1941 by a team led by Glenn T. Seaborg, including Arthur C. Wahl, Joseph W. Kennedy, and Emilio Segrè, also at Berkeley.[23] The synthesis involved bombarding uranium with deuterons in the 60-inch cyclotron to produce neptunium, followed by neutron irradiation to yield plutonium-239, which was chemically identified as a distinct element.[23] This discovery rapidly became central to the Manhattan Project, the U.S. wartime effort to develop nuclear weapons, as plutonium-239 proved highly fissionable and suitable for bomb cores.[24] Large-scale production of plutonium commenced in 1944 at the Hanford Site in Washington state, where graphite-moderated reactors irradiated uranium fuel to generate the isotope in kilogram quantities for the atomic bombs used in 1945.[24] During the final years of World War II, further advances led to the synthesis of americium (atomic number 95) in July 1944 and curium (atomic number 96) later that year, both by Seaborg's group at Berkeley under Manhattan Project auspices.[23] Americium was produced through intense neutron bombardment of plutonium-239 in a nuclear reactor, yielding americium-241 via successive beta decays.[23] Curium-242 was synthesized by bombarding plutonium-239 with helium ions (alpha particles) in the 60-inch cyclotron, marking the first use of charged-particle acceleration for transuranium elements beyond plutonium.[23] Postwar research at Berkeley continued the synthesis of heavier actinides. Berkelium (97) was discovered in 1949 by bombarding americium-241 with alpha particles. Californium (98) followed in 1950 via helium-ion bombardment of curium-242. Einsteinium (99) and fermium (100) were identified in 1952 from debris of the first thermonuclear explosion (Ivy Mike). Mendelevium (101) was synthesized in 1955 by alpha bombardment of einsteinium-253. Nobelium (102) was reported in 1958 by Berkeley via helium-ion bombardment of curium, though a competing claim from Dubna was also noted. Lawrencium (103) was produced in 1961 at Berkeley using the heavy-ion linear accelerator (HILAC) to bombard californium-252 with boron-10 or boron-11 ions.[25] These early syntheses were driven by the urgent demands of World War II for fissile materials in nuclear weapons, with initial production focused almost exclusively on plutonium at sites like Hanford to support the Allied war effort.[24] Following the war's end in 1945, research transitioned to peacetime applications, with declassified efforts at Berkeley emphasizing fundamental studies of transuranium properties and extensions to heavier elements for scientific understanding rather than weaponry.[23] Throughout these wartime and immediate postwar experiments, researchers faced significant challenges, including extremely low yields—often on the order of micrograms or less—and intense radiation hazards that necessitated remote handling and rigorous safety protocols to mitigate health risks from alpha, beta, and gamma emissions.[23]Modern Discoveries
The discoveries of transuranium elements from the 1970s onward marked a shift toward international competition and advanced nuclear synthesis techniques, building on earlier actinide work. Elements 104 (rutherfordium) and 105 (dubnium) were first synthesized in the late 1960s and early 1970s through heavy-ion fusion reactions by rival teams at Lawrence Berkeley National Laboratory (LBNL) in the United States and the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The Berkeley team reported element 104 in 1969 using a californium-249 target bombarded with carbon-12 ions, while Dubna claimed it the same year via plutonium-242 and neon-22. Similarly, element 105 emerged in 1970 from both labs, with Berkeley using californium-249 and nitrogen-15, and Dubna employing titanium-50 on americium-243. These overlapping claims sparked the "Transfermium Wars," a decade-long dispute over priority, resolved in 1997 by the International Union of Pure and Applied Chemistry (IUPAC) and International Union of Pure and Applied Physics (IUPAP) Joint Working Party, which credited both teams but assigned the names rutherfordium (after Ernest Rutherford) and dubnium (honoring the Dubna lab).[9][26] The synthesis of transactinides (elements 106 through 112) in the 1970s to 1990s involved further refinements in accelerator technology and separation methods, primarily at LBNL, JINR-Dubna, and the Gesellschaft für Schwerionenforschung (GSI) in Germany. Element 106 (seaborgium) was produced in 1974 at Berkeley via the reaction of californium-249 with oxygen-18 ions, but its naming ignited controversy when the lab proposed "seaborgium" in 1994 to honor living chemist Glenn T. Seaborg; IUPAC initially rejected it in 1997, citing a tradition against naming elements after living individuals, though the name was ultimately approved after Seaborg's death in 1999. GSI took the lead for elements 107 (bohrium, 1981, via bismuth-209 and chromium-54), 108 (hassium, 1984, using lead-208 and iron-58), and 109 (meitnerium, 1982 and confirmed 1989 with bismuth-209 and iron-58), all verified through alpha-decay chains linking to known isotopes. Elements 110 (darmstadtium, 1994, lead-208 and nickel-62), 111 (roentgenium, 1994, bismuth-209 and nickel-64), and 112 (copernicium, 1996, lead-208 and zinc-70) were also synthesized at GSI using "cold fusion" reactions, with IUPAC confirmations in 2003, 2004, and 2010, respectively. These discoveries relied heavily on in-flight separators like GSI's SHIP to isolate short-lived isotopes, confirmed by genetic decay sequences terminating in established nuclei such as dubnium or rutherfordium.[9][27][28][29][30] Superheavy elements 113 through 118 were confirmed between 2004 and 2016 through collaborative efforts emphasizing "hot fusion" with calcium-48 beams at JINR-Dubna and RIKEN in Japan, alongside GSI contributions. RIKEN's 2004 synthesis of element 113 (nihonium) via bismuth-209 and zinc-70 was independently verified in 2012, leading to its 2016 IUPAC naming after Japan. Dubna's team, often partnering with U.S. labs like Oak Ridge and Lawrence Livermore, produced element 114 (flerovium, 1998, plutonium-244 and calcium-48) confirmed in 2012; element 115 (moscovium, 2003, americium-243 and calcium-48) and 117 (tennessine, 2010, berkelium-249 and calcium-48) in 2016; element 116 (livermorium, 2000, curium-248 and calcium-48) in 2012; and element 118 (oganesson, 2002, californium-249 and calcium-48) in 2016. Validation hinged on multi-step alpha-decay chains, with isotopes like ^{294}Ts decaying through six alphas to anchor at known livermorium, ensuring unambiguous identification despite production rates of mere atoms per experiment. These efforts resolved prior disputes through rigorous cross-laboratory confirmations by IUPAC/IUPAP panels.[9][31] As of 2025, attempts to synthesize element 119 (ununennium) continue at RIKEN and GSI, using reactions like vanadium-51 on curium-248 or titanium-50 on berkelium-249, though no confirmed production has occurred amid challenges from geopolitical tensions and low cross-sections. RIKEN leads with its upgraded accelerator, aiming for single-atom detections via decay chain analysis to known superheavies.[32][33]Production Methods
Nuclear Reactions
Transuranium elements are primarily synthesized through nuclear reactions that overcome the inherent instability of nuclei beyond uranium. For the lighter actinides, such as neptunium, plutonium, and americium, production relies on successive neutron capture followed by beta decay in nuclear reactors or accelerators. In this process, uranium-238 captures a thermal neutron to form uranium-239, which undergoes beta decay to neptunium-239, and subsequently to plutonium-239: This chain can continue with additional neutron captures and decays to yield heavier isotopes, leveraging the availability of uranium fuel and the relatively high neutron fluxes in reactors.[34][35] For superheavy elements (Z ≥ 104), the dominant method is heavy-ion fusion-evaporation reactions, where a lighter projectile ion is accelerated to fuse with a heavy target nucleus, forming a compound nucleus at excitation energies of 10–40 MeV. The compound nucleus then evaporates neutrons to reach a more stable configuration. A representative example is the synthesis of flerovium (element 114), achieved via the reaction of calcium-48 with plutonium-244: Such "hot fusion" reactions, often using neutron-rich projectiles like ^{48}Ca, target even-Z actinides to maximize survival probability against fission. Recent advances include the use of titanium-50 beams, demonstrated in 2024 at Lawrence Berkeley National Laboratory, where ^{50}Ti + ^{242}Pu produced livermorium (element 116) isotopes, offering a pathway to synthesize element 120 via ^{50}Ti + ^{249}Cf and potentially reaching the island of stability.[36] As an alternative for producing neutron-rich isotopes of transuranium elements, multinucleon transfer (MNT) reactions involve grazing collisions between heavy ions, where protons and neutrons are exchanged without full fusion. These reactions, such as ^{238}U + ^{248}Cm, favor the formation of neutron-excess nuclei in the transuranium region (Z ≥ 93) by transferring multiple nucleons across the Coulomb barrier at energies near or below it, potentially accessing isotopes closer to the island of stability.[37][38] The feasibility of these reactions hinges on Q-value calculations, which determine the energy release or absorption (Q = [mass of reactants - mass of products] c²). Positive Q-values indicate exothermic reactions, but for superheavy synthesis, they are often negative, requiring beam energies above the interaction barrier. The Coulomb barrier, arising from electrostatic repulsion between positively charged nuclei, is given approximately by V_B ≈ (Z_1 Z_2 e²)/(4πε_0 r), where Z_1 and Z_2 are atomic numbers, e is the elementary charge, and r is the interaction radius (typically 1.2(A_1^{1/3} + A_2^{1/3}) fm). Projectiles must tunnel through this barrier via quantum effects, with the barrier height for superheavy systems exceeding 200 MeV due to high Z products. Once fused, the compound nucleus dissipates excitation energy through neutron evaporation and intrinsic dissipation mechanisms, such as single-particle excitations and collective vibrations, which compete with fission to determine survival yield.[39][40][41] Production yields are extremely low, with fusion-evaporation cross-sections for superheavy elements typically on the order of 1 picobarn (10^{-36} cm²), resulting in single-atom detections after prolonged irradiations. MNT reactions offer higher cross-sections (up to nanobarns) for neutron-rich isotopes but still yield femto- to picogram quantities. These minuscule probabilities underscore the precision required in beam energy optimization around the barrier to balance fusion probability and fission suppression.[42][43]Facilities and Techniques
The production of transuranium elements, particularly superheavy ones, relies on specialized accelerator facilities equipped with high-intensity ion beams and precise separation systems. Early efforts at Lawrence Berkeley National Laboratory utilized cyclotrons, such as the 60-inch model, to synthesize initial transuranium elements like neptunium, plutonium, americium, and curium through targeted bombardments.[44][45] Today, the laboratory's 88-Inch Cyclotron continues to support heavy element research with capabilities for fusion-evaporation reactions, including the 2024 demonstration of titanium-50 beams for livermorium production.[46][36] Internationally, the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, operates the Superheavy Element Factory, featuring the DC280 cyclotron, which delivers intense heavy-ion beams for synthesizing elements beyond uranium. Operational since late 2019, it has enabled discoveries such as new isotopes of livermorium (288, 289) and copernicium (280) as of July 2025, with beam intensities reaching up to 10 particle microamperes for various ions.[47][48][49] The GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, employs the SHIP (Separator for Heavy Ion Products) velocity filter, an electromagnetic device optimized for isolating fusion products in cold fusion reactions with lead or bismuth targets.[50][51] In Japan, RIKEN's Nishina Center utilizes the GARIS (Gas-filled Recoil Ion Separator), a system designed for efficient separation and detection of superheavy residues from hot fusion reactions, supporting ongoing searches for element 119 using vanadium-51 beams on curium-248 targets as of 2025.[52][53][32] Key techniques for isolating transuranium products include gas-filled separators, which exploit the charge-state equilibrium of recoiling ions in a gas medium to magnetically separate them from the primary beam and scattered particles, achieving high transmission efficiencies for short-lived isotopes.[54][55] Digital implantation detectors, typically arrays of double-sided silicon strip detectors (DSSDs), capture the implanted recoils and subsequent alpha decay chains, enabling precise correlation of events through position-sensitive tracking and energy measurements.[56][57] Upgrades continue to enhance production; for instance, RIKEN's GARIS-III separator supports intensified efforts for element 119.[58][59] Detection of individual transuranium atoms involves time-of-flight (TOF) measurements along the separator path, combined with energy loss profiling in foils or gases, to confirm the mass-to-charge ratio and discriminate against background events, ensuring unambiguous identification of rare decay sequences.[60][61]Properties
Physical Properties
Transuranium elements exhibit a wide range of physical properties influenced by their high atomic numbers and nuclear instability. These elements, spanning atomic numbers 93 to 118, are all radioactive, with isotopes displaying half-lives from millions of years to fractions of a second. Their metallic nature is marked by high densities and varying melting points, though trends deviate from lighter actinides due to electronic and nuclear effects.[62][63] The atomic masses of transuranium isotopes typically range from around 225 to 294 atomic mass units, with multiple isotopes per element due to synthetic production methods. For instance, neptunium-237, the longest-lived isotope of neptunium (atomic number 93), has an atomic mass of 237 u and a half-life of 2.14 million years. Plutonium-244, the most stable isotope of plutonium (atomic number 94), possesses an atomic mass of 244 u and a half-life of 80.8 million years. In contrast, superheavy elements like oganesson (atomic number 118) have only trace isotopes; oganesson-294, with an atomic mass of 294 u, has a half-life of approximately 0.89 milliseconds. These half-lives decrease dramatically with increasing atomic number, reflecting the growing instability of the nucleus.[62][20][64]| Element | Representative Isotope | Atomic Mass (u) | Half-Life |
|---|---|---|---|
| Neptunium | ^{237}Np | 237 | 2.14 × 10^6 years[62] |
| Plutonium | ^{244}Pu | 244 | 8.08 × 10^7 years[20] |
| Curium | ^{247}Cm | 247 | 1.6 × 10^7 years[65] |
| Oganesson | ^{294}Og | 294 | 0.89 ms[64] |