Extinct isotopes of superheavy elements

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Extinct isotopes of superheavy elements are isotopes of superheavy elements whose half-lives were too short to have lasted through the formation of the Solar System, [1] and because they are not replenished by natural processes, can nowadays only be found as their decay products (from alpha decay, cluster decay or spontaneous fission) trapped within sediment and meteorite samples dating billions of years ago.

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Carbonaceous chondrite fission xenon

Carbonaceous chondrite fission xenon (CCF Xe), are a collection of different isotopes of xenon that were thought to have arisen from the decay of a superheavy element within the island of stability. Early studies proposed that the half life of the theoretical progenitor of CCF Xe to be on the order of 108 years. [2] A later attempt at characterization of the progenitor in 1975 by Edward Anders, a professor of chemistry at the University of Chicago, and colleague John Larimer suggested a heat of vaporization of 54 kJ/mol and a boiling point of 2500K for the element and, based on estimated accretion temperatures, they also proposed elements 111 and 115 (today named roentgenium and moscovium) as the most likely candidates assuming the element condensed in pure form. [3]

Allende meteorite

Anders went on to study samples of the Allende meteorite, the largest carbonaceous chondrite ever found on Earth. Results of these studies suggested elements 111–115 (today roentgenium, copernicium, nihonium, flerovium, and moscovium) [4] as the most likely candidates for the progenitor of CCF Xe. These studies also proposed that the progenitor condensed as an iron chromium sulfide. [5] This was later called into question as iron chromium sulfide is very rare with a relative abundance of 0.4%. [6]

Evidence against carbonaceous fission xenon

By the 1980s, CCF Xe actually being the product of fission was doubtful, and the alternate theory that it had arisen from r-process (neutron capture) nucleosynthesis gained more ground. [7] Researchers looked at the isotopic anomalies in nearby elements samarium, neodymium, and barium, and compared to the amount of xenon. Whether CCF Xe was produced by nucleosynthesis or fission, comparable amounts of barium-135 should be produced. [6] When researchers compared the experimental data to predicted amounts of Barium following each model, neither model came close to predicting the anomalies correctly, leading to Lewis et al. calling the experiment an "embarrassment" for both models.[ citation needed ] However, in the case of nucleosynthesis, it is possible that samarium, neodymium, and barium were separated from Xe by prior condensation in the supernova shell or plasma processes. [6] Based on this data it was deemed unlikely that CCF Xe had actually arose from fission.

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Bohrium is a synthetic chemical element; it has symbol Bh and atomic number 107. It is named after Danish physicist Niels Bohr. As a synthetic element, it can be created in particle accelerators but is not found in nature. All known isotopes of bohrium are highly radioactive; the most stable known isotope is 270Bh with a half-life of approximately 2.4 minutes, though the unconfirmed 278Bh may have a longer half-life of about 11.5 minutes.

Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of Earth itself, and can also be used to date a wide range of natural and man-made materials.

<span class="mw-page-title-main">Xenon</span> Chemical element with atomic number 54 (Xe)

Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.

<span class="mw-page-title-main">Stable nuclide</span> Nuclide that does not undergo radioactive decay

Stable nuclides are isotopes of a chemical element whose nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The nuclei of such isotopes are not radioactive and unlike radionuclides do not spontaneously undergo radioactive decay. When these nuclides are referred to in relation to specific elements they are usually called that element's stable isotopes.

Roentgenium is a synthetic chemical element; it has symbol Rg and atomic number 111. It is extremely radioactive and can only be created in a laboratory. The most stable known isotope, roentgenium-282, has a half-life of 130 seconds, although the unconfirmed roentgenium-286 may have a longer half-life of about 10.7 minutes. Roentgenium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the physicist Wilhelm Röntgen, who discovered X-rays. Only a few roentgenium atoms have ever been synthesized, and they have no practical application.

<span class="mw-page-title-main">Natural abundance</span> Relative proportion of an isotope as found in nature

In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time.

Livermorium is a synthetic chemical element; it has symbol Lv and atomic number 116. It is an extremely radioactive element that has only been created in a laboratory setting and has not been observed in nature. The element is named after the Lawrence Livermore National Laboratory in the United States, which collaborated with the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, to discover livermorium during experiments conducted between 2000 and 2006. The name of the laboratory refers to the city of Livermore, California, where it is located, which in turn was named after the rancher and landowner Robert Livermore. The name was adopted by IUPAC on May 30, 2012. Five isotopes of livermorium are known, with mass numbers of 288 and 290–293 inclusive; the longest-lived among them is livermorium-293 with a half-life of about 80 milliseconds. A sixth possible isotope with mass number 294 has been reported but not yet confirmed.

Oganesson is a synthetic chemical element; it has symbol Og and atomic number 118. It was first synthesized in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, near Moscow, Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by the Joint Working Party of the international scientific bodies IUPAC and IUPAP. It was formally named on 28 November 2016. The name honors the nuclear physicist Yuri Oganessian, who played a leading role in the discovery of the heaviest elements in the periodic table. It is one of only two elements named after a person who was alive at the time of naming, the other being seaborgium, and the only element whose eponym is alive as of 2024.

<span class="mw-page-title-main">Island of stability</span> Predicted set of isotopes of relatively more stable superheavy elements

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 nuclides, separated from known stable and long-lived primordial radionuclides. Its theoretical existence is attributed to stabilizing effects of predicted "magic numbers" of protons and neutrons in the superheavy mass region.

Moscovium is a synthetic chemical element; it has symbol Mc and atomic number 115. It was first synthesized in 2003 by a joint team of Russian and American scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. In December 2015, it was recognized as one of four new elements by the Joint Working Party of international scientific bodies IUPAC and IUPAP. On 28 November 2016, it was officially named after the Moscow Oblast, in which the JINR is situated.

<span class="mw-page-title-main">Presolar grains</span> Very old dust in space

Presolar grains are interstellar solid matter in the form of tiny solid grains that originated at a time before the Sun was formed. Presolar grains formed within outflowing and cooling gases from earlier presolar stars. The study of presolar grains is typically considered part of the field of cosmochemistry and meteoritics.

The slow neutron-capture process, or s-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The s-process is responsible for the creation (nucleosynthesis) of approximately half the atomic nuclei heavier than iron.

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 the periodic table; the last actinide is lawrencium. By definition, superheavy elements are also transuranium elements, i.e., having atomic numbers greater than that of uranium (92). Depending on the definition of group 3 adopted by authors, lawrencium may also be included to complete the 6d series.

Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm and 148Sm, with 152Sm being the most abundant. 146Sm is also fairly long-lived, but is not long-lived enough to have survived in significant quantities from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System as an extinct radionuclide. It is the longest-lived nuclide that has not yet been confirmed to be primordial.

Naturally occurring xenon (54Xe) consists of seven stable isotopes and two very long-lived isotopes. Double electron capture has been observed in 124Xe and double beta decay in 136Xe, which are among the longest measured half-lives of all nuclides. The isotopes 126Xe and 134Xe are also predicted to undergo double beta decay, but this process has never been observed in these isotopes, so they are considered to be stable. Beyond these stable forms, 32 artificial unstable isotopes and various isomers have been studied, the longest-lived of which is 127Xe with a half-life of 36.345 days. All other isotopes have half-lives less than 12 days, most less than 20 hours. The shortest-lived isotope, 108Xe, has a half-life of 58 μs, and is the heaviest known nuclide with equal numbers of protons and neutrons. Of known isomers, the longest-lived is 131mXe with a half-life of 11.934 days. 129Xe is produced by beta decay of 129I ; 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, so are used as indicators of nuclear explosions.

Meitnerium (109Mt) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 266Mt in 1982, and this is also the only isotope directly synthesized; all other isotopes are only known as decay products of heavier elements. There are eight known isotopes, from 266Mt to 278Mt. There may also be two isomers. The longest-lived of the known isotopes is 278Mt with a half-life of 8 seconds. The unconfirmed heavier 282Mt appears to have an even longer half-life of 67 seconds.

Roentgenium (111Rg) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 272Rg in 1994, which is also the only directly synthesized isotope; all others are decay products of heavier elements. There are seven known radioisotopes, having mass numbers of 272, 274, and 278–282. The longest-lived isotope is 282Rg with a half-life of about 2 minutes, although the unconfirmed 283Rg and 286Rg may have longer half-lives of about 5.1 minutes and 10.7 minutes respectively.

<span class="mw-page-title-main">Plutonium-244</span> Isotope of plutonium

Plutonium-244 (244Pu) is an isotope of plutonium that has a half-life of 80 million years. This is longer than any of the other isotopes of plutonium and longer than any other actinide isotope except for the three naturally abundant ones: uranium-235, uranium-238, and thorium-232. Given the mathematics of the decay of plutonium-244, an exceedingly small amount should still be present in the Earth's composition, making plutonium a likely although unproven candidate as the shortest-lived primordial element.

An extinct radionuclide is a radionuclide that was formed by nucleosynthesis before the formation of the Solar System, about 4.6 billion years ago, but has since decayed to virtually zero abundance and is no longer detectable as a primordial nuclide. Extinct radionuclides were generated by various processes in the early Solar system, and became part of the composition of meteorites and protoplanets. All widely documented extinct radionuclides have half-lives shorter than 100 million years.

Xenon isotope geochemistry uses the abundance of xenon (Xe) isotopes and total xenon to investigate how Xe has been generated, transported, fractionated, and distributed in planetary systems. Xe has nine stable or very long-lived isotopes. Radiogenic 129Xe and fissiogenic 131,132,134,136Xe isotopes are of special interest in geochemical research. The radiogenic and fissiogenic properties can be used in deciphering the early chronology of Earth. Elemental Xe in the atmosphere is depleted and isotopically enriched in heavier isotopes relative to estimated solar abundances. The depletion and heavy isotopic enrichment can be explained by hydrodynamic escape to space that occurred in Earth's early atmosphere. Differences in the Xe isotope distribution between the deep mantle, shallower Mid-ocean Ridge Basalts (MORBs), and the atmosphere can be used to deduce Earth's history of formation and differentiation of the solid Earth into layers.

References

  1. ↑ Turner, Grenville; Harrison, T. Mark; Holland, Greg; Mojzsis, Stephen J.; Gilmour, Jamie (2004-01-01). "Extinct 244Pu in Ancient Zircons". Science. 306 (5693): 89–91. Bibcode:2004Sci...306...89T. doi:10.1126/science.1101014. JSTOR   3839259. PMID   15459384. S2CID   11625563.
  2. ↑ Schramm, David N. (1971-09-24). "Implied Superheavy Element Decay Lifetime from Meteorites". Nature. 233 (5317): 258–260. Bibcode:1971Natur.233..258S. doi:10.1038/233258a0. PMID   16063318. S2CID   4171749.
  3. ↑ Anders, Edward; Larimer, John W. (1972-01-01). "Extinct Superheavy Element in Meteorites: Attempted Characterization". Science. 175 (4025): 981–983. Bibcode:1972Sci...175..981A. doi:10.1126/science.175.4025.981. JSTOR   1732722. PMID   17791931. S2CID   24652899.
  4. ↑ Anders, Edward; Lewis, R.S. (1981-03-01). "XE129 and the Origin of CCF Xenon in Meteorites". LUNAR AND PLANETARY SCIENCE XII, P. 616-618. Abstract.: 616. Bibcode:1981LPI....12..616L.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ↑ Anders, Edward; Higuchi, H.; Gros, Jacques; Takahashi, H.; Morgan, John W. (1975-01-01). "Extinct Superheavy Element in the Allende Meteorite". Science. 190 (4221): 1262–1271. Bibcode:1975Sci...190.1262A. doi:10.1126/science.190.4221.1262. JSTOR   1741804. S2CID   96924953.
  6. 1 2 3 Lewis, R. S.; Anders, E.; Shimamura, T.; Lugmair, G. W. (1983-01-01). "Barium Isotopes in Allende Meteorite: Evidence against an Extinct Superheavy Element". Science. 222 (4627): 1013–1015. Bibcode:1983Sci...222.1013L. doi:10.1126/science.222.4627.1013. JSTOR   1691282. PMID   17776244. S2CID   532158.
  7. ↑ Black, David C. (1975-02-06). "Alternative hypothesis for the origin of CCF xenon". Nature. 253 (5491): 417–419. Bibcode:1975Natur.253..417B. doi:10.1038/253417a0. S2CID   4293499.
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