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dubnium. Dubnium is a synthetic chemical element; it has symbol Db and atomic number 105. It is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of about 16 hours. This greatly limits extended research on the element.
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ChemicalElement
seaborgium. Seaborgium is a synthetic chemical element; it has symbol Sg and atomic number 106. It is named after the American nuclear chemist Glenn T. Seaborg. As a synthetic element, it can be created in a laboratory but is not found in nature. It is also radioactive; the most stable known isotopes have half-lives on the order of several minutes.
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bohrium. 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.
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wikidata.org 12 views · 1mo ago
ChemicalElement
hassium. Hassium is a synthetic chemical element; it has symbol Hs and atomic number 108. It is highly radioactive: its most stable known isotopes have half-lives of about ten seconds. One of its isotopes, 270Hs, has magic numbers of protons and neutrons for deformed nuclei, giving it greater stability against spontaneous fission. Hassium is a superheavy element; it has been produced in a laboratory in very small quantities by fusing heavy nuclei with lighter ones. Natural occurrences of hassium have been hypothesized but never found.
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wikidata.org 12 views · 1mo ago
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meitnerium. Meitnerium is a synthetic chemical element; it has symbol Mt and atomic number 109. It is an extremely radioactive synthetic element. The most stable known isotope, meitnerium-278, has a half-life of 4.5 seconds, although the unconfirmed meitnerium-282 may have a longer half-life of 67 seconds. The element was first synthesized in August 1982 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, and it was named after the Austrian-Swedish nuclear physicist Lise Meitner in 1997.
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wikidata.org 12 views · 1mo ago
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darmstadtium. Darmstadtium is a synthetic chemical element; it has symbol Ds and atomic number 110. It is extremely radioactive: the most stable known isotope, darmstadtium-281, has a half-life of approximately 14 seconds. Darmstadtium was first created in November 1994 by the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, after which it was named.
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wikidata.org 13 views · 1mo ago
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roentgenium. 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 December 1994 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the physicist Wilhelm R??ntgen, who discovered X-rays. Only a few roentgenium atoms have ever been synthesized, and they have no practical application.
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lawrencium. Lawrencium is a synthetic chemical element; it has symbol Lr and atomic number 103. It is named after Ernest Lawrence, inventor of the cyclotron, a device used to discover many artificial radioactive elements. A radioactive metal, lawrencium is the eleventh transuranium element, the third transfermium, and the last member of the actinide series. Like all elements with atomic number over 100, lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles. Fourteen isotopes of lawrencium are known; the most stable is 266Lr with half-life 11 hours, but the shorter-lived 260Lr is most commonly used in chemistry because it can be produced on a larger scale.
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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 Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.
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wikidata.org 12 views · 1mo ago
nobelium. Nobelium is a synthetic chemical element; it has symbol No and atomic number 102. It is named after Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranium element, the second transfermium, and is the fourteenth member of the actinide series. Like all elements with atomic number over 100, nobelium can only be produced in particle accelerators by bombarding lighter elements with charged particles. A total of twelve nobelium isotopes are known to exist; the most stable is 259No with a half-life of 58 minutes, but the shorter-lived 255No is most commonly used in chemistry because it can be produced on a larger scale.
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mendelevium. Mendelevium is a synthetic chemical element; it has symbol Md 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 in macroscopic quantities by neutron bombardment of lighter elements. It is the thirteenth actinide, the ninth transuranic element, and the first transfermium; it is named after Dmitri Mendeleev, the father of the periodic table.
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fermium. Fermium is a synthetic chemical element; it has symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not been prepared yet. A total of 20 isotopes are known, with 257Fm being the longest-lived with a half-life of 100.5 days.
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einsteinium. Einsteinium is a synthetic chemical element; it has symbol Es and atomic number 99 and is a member of the actinide series and the seventh transuranium element.
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wikidata.org 12 views · 1mo ago
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 intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium with alpha particles. This was then sent to the Metallurgical Laboratory at the University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors ??? one tonne of spent nuclear fuel contains ~20 grams of curium.
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americium. Americium is a synthetic chemical element; it has 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 europium and was thus named after the Americas by analogy.
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californium. Californium is a synthetic chemical element; it has symbol Cf and atomic number 98. It was first synthesized in 1950 at Lawrence Berkeley National Laboratory by bombarding curium with alpha particles. It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all elements that have been produced in amounts large enough to see with the naked eye. It was named after the university and the U.S. state of California.
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neptunium. Neptunium is a chemical element; it has symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar System, which uranium is named after. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. Like all actinides, it is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.
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plutonium. Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.
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radium. Radium is a chemical element; it has symbol Ra and atomic number 88. It is the sixth element in group??2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1,600??years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radioluminescence. For this property, it was widely used in self-luminous paints following its discovery. Of the radioactive elements that occur in quantity, radium is considered particularly toxic, and it is carcinogenic due to the radioactivity of both it and its immediate decay product radon as well as its tendency to accumulate in the bones.
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thorium. Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.
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radon. Radon is a chemical element; it has symbol Rn and atomic number 86. It is a radioactive noble gas and is colorless and odorless. Of the three naturally occurring radon isotopes, only 222Rn has a sufficiently long half-life for it to be released from the soil and rock where it is generated. Radon isotopes are the immediate decay products of radium isotopes.
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protactinium. Protactinium is a chemical element; it has symbol Pa and atomic number 91. It is a dense, radioactive, silvery-gray actinide metal which readily reacts with oxygen, water vapor, and inorganic acids. It forms various chemical compounds, in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity, and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.
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actinium. Actinium is a chemical element; it has symbol Ac and atomic number??89. It was discovered by Friedrich Oskar Giesel in 1902, who gave it the name emanium; the element got its name by being wrongly identified with a substance Andr??-Louis Debierne found in 1899 and called actinium. The actinide series, a set of 15 elements between actinium and lawrencium in the periodic table, is named after actinium. Together with polonium, radium, and radon, actinium was one of the first non-primordial radioactive elements to be discovered.
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francium. Francium is a chemical element; it has symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223, has a half-life of only 22??minutes. It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element. Francium's isotopes decay quickly into astatine, radium, and radon. The electronic structure of a francium atom is [Rn] 7s1; thus, the element is classed as an alkali metal.
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