Half-life transuranium elements

Dmitri Mendeleev) Mendelevium, the ninth transuranium element of the actinide series discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope 253Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was 256Md, which has a half-life of 76 min. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis. 

Like einsteinium, this unstable element was discovered in the fallout from the first hydrogen bomb. To date, only fragments in microgram amounts can be isolated. 258Fm ends the series of transuranium elements that can be produced in a reactor by neutron bombardment. The longest-lived isotope decays with a half-life of 100 days... 

Seaborgium - the atomic number is 106 and the chemical symbol is Sg. The name derives from the American chemist Glenn Theodore Seaborg , who led a team that first synthesized a number of transuranium elements. The element Seaborgium was first synthesized by American scientists from the University of California lab in Berkeley, California imder Albert Ghiorso, who used the nuclear reaction Cf ( 0,4n) Sg. The longest half-life associated with this unstable element is 21 second Sg. 

Symbol Cf atomic number 98 atomic weight 251 (the principal isotope) californium is a transuranium radioactive actinide element electron configuration [Rn]5/i°7s2 valence state +3 most stable isotope Cf, half-life 800 years isotope properties are presented below ... 

Symbol Lr atomic number 103 atomic weight 262 a transuranium inner-transition actinide series element a synthetic radioactive element electron configuration [RnjTs b/ Sdi valence +3 six isotopes of masses 255 to 260 have been synthesized longest-lived known isotope Lr-260 has half-life of 3 minutes. 

The element first was made by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in 1955 in Berkeley, California. It was synthesized by bombardment of einsteinium-253 with alpha particles of 41 MeV energy in a 60-inch cyclotron. The element was named Mendelevium in honor of Russian chemist Dimitri Mendeleev. Mendelevium —258 isotope with a half-life of 60 days was discovered in 1967. The element has no commercial use except in research to synthesize isotopes of other transuranium elements. 

Neptunium, the first transuranium element, was discovered hy E. M. McMdlan and P. H. Ahelson in 1940 in Berkeley, California. It was produced in the cyclotron in a nuclear reaction by bombarding uranium-238 with neutrons. An isotope of mass 239 and atomic number 93 and ti/2 of 2.4 days was produced in this reaction. Neptunium-237, the longest-lived alpha-emitter with half-life 2.14x10 years, was discovered two years later in 1942 by Wahl and Seaborg. The new element was named after the planet Neptune, the planet next to Uranus in the solar system. 

CURIUM. CAS 7440-51-9], Chemical element- symbol Cm. at. no. 96, at. wt. 247 (mass number of the most stable isotope i, radioactive metal of the Actinide series, also one of Ihe Transuranium elements, mp estimated 1350 50 C. l7CTn has a half-life of 1.64 x It)7 years, Olher long-lived isotopes arc J,Cm (ti j =9320 years), 4, Cm = 54X0 years I. "Cm... 

NEPTUNIUM. [CAS 7439-99-8]. Chemical element, symbol Np, at. no, 93, at. wt, 237,0482 (predominant isotope), radioactive metal of the Actinide series, also one of the Transuranium elements. Neptunium was the first of [he Transuranium elements [o be discovered and was first produced by McMillan and Abelson (1940) at the University of California at Berkeley. This was accomplished by bombarding uranium with neutrons. Neptunium is produced as a by-pruduct from nuclear reactors. 237Np is the most stable isotope, with a half-life of 2.20 x 106 years, The only other very long-lived isotope is that of mass number 236. with a half-life of 5 x 10- years. 

Transuranium elements (above atomic number 92) were believed not to occur in nature because of their relatively short half-lives. Then 244Pu was reported in natural ore. The half-life of 244Pu is 8.0 x 107 years. If this element is more stable than any of its radioactive predecessors and has not been produced in this ore in significant amounts since the ore was deposited, what fraction of the original244Pu content would still be present Assume the ore is 5 x 109 years old. 

Since the uranyl ion is so obviously its own category, it is very interesting to compare with the analogous species formed by transuranium elements. M = Np, Pu and Am form all three MO 72 and MO which are, by no means, the most stable oxidation states of their elements, and which tend toward reduction by the radiochemical products concomitant with the high specific radioactivity of the isotopes normally studied of plutonium and americium (whereas e.g. 244Pu with the half-life 82 million years would not present this problem). Contrary to some reports in literature, it does not seem that curium (and the subsequent elements) form such dioxo complexes. 

The discovery of Pu has been described in detail by Seaborg in his Plutonium Story (chapter 1 of the book The Transuranium Elements 1958). First, the separation of Pu from Th caused some difficulties, because both elements were in the oxidation state 4-4. After oxidation of Pu(IV) by persulfate to Pu(VI), separation became possible. Pu is produced in appreciable amounts in nuclear reactors (section 14.1), but it has not immediately been detected, due to its low specific activity caused by its long half-life. After the discovery of Pu, plutonium gained great practical importance, because of the high fission cross section of Pu by thermal neutrons. Very small amounts of Pu are present in uranium ores, due to (n, y) reaction of neutrons from cosmic radiation with The ratio Pu/ U is of the order of 10 In 1971, the longest-lived isotope of plutonium, Pu (ri/2 = 8.00 lO y) was found by Hoffman in the Ce-rich rare-earth mineral bastnaesite, in concentrations of the order of 10 gAg-... 

The half-lives of the longest-lived isotopes of transuranium elements (Fig. 14.8) show a continuous exponential decrease with increasing atomic number Z. Whereas up to element 103 the half-life is mainly determined by a decay, the influence of spontaneous fission seems to become predominant for elements with Z > 106. The drop model of nuclei predicts a continuous decrease of the fission barrier from about 6 MeV for uranium to about zero for element 110. That means that according to the drop model, elements with Z > 110 are not expected to exist, because normal vibrations of the nuclei should lead to fission. 

The isolation of the long-lived and highly dangerous transuranium elements reduces the control time over the waste from the scale of millions to that of hundreds of years, since about 300 years are 10 x the half life time of the longest lived fission product Sr-90. The potential danger is reduced in the same scale. 

In addition to stable elements, radioactive elements are also produced in stars. The unstable but relatively long-lived isotopes °K, Th, and are the internal heat source that drives volcanic activity and processes related to internal convection in the terrestrial planets. The short-lived transuranium elements such as Rn and Ra that are found on the Earth are all products of U and Th decay. These isotopes are sometimes used as tracers of natural terrestrial processes and cycles. Long-lived isotopes, such as Rb and Sm, are used for the precise dating of geological samples. When the solar system formed, it also contained several short-lived isotopes that have since decayed and are now extinct in natural wstems. These include A1, Pu, Pd, and 1. Al, with a half-life of less than 1 Ma, is particularly important because it is a potentially powerful heat source for planetary bodies and because its existence in the early solar system places tight constraints on the early solar system chronology. 

Mendelevium — (Dmitri Mendeleev [1834-1907]), Md at. wt. (258) at. no. 101 m.p. 827°C valence +2, +3. Mendelevium, the ninth transuranium element of the actinide series to be discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg early in 1955 as a result of the bombardment of the isotope Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was Md, which has a half-life of 78 min. This first identification was notable in that Md was synthesized on a one-atom-at-a-time basis. Nineteen isotopes and isomers are now recognized. Md has a half-life of 51.5 days. This isotope has been produced by the bombardment of an isotope of einsteinium with ions of helium. It now appears possible that eventually enough Md can be made so that some of its physical properties can be determined. Md has been used to elucidate some of the chemical properties of mendelevium in aqueous solution. Experiments seem to show that the element possesses a moderately stable dipositive (II) oxidation state in addition to the tripositive (III) oxidation state, which is characteristic of actinide elements. 

Positron production Electron capture Decay series Nuclear transformation Transuranium elements Geiger-Miiller counter Scintillation counter Half-life... 

Many transuranium elements, such as plutonium-232, have very short half-lives. (For Pu, the half-life is 36 minutes.) However, some, like protactinium-231 (half-life = 3.34 X 10 years), have relatively long half-lives. Use the masses given in the following table to calculate the change in energy when 1 mol Pu nuclei and 1 mol Pa nuclei are each formed from their respective number of protons and neutrons. 

A recently reported synthesis of the transuranium element bohrium (Bh) involved the bombardment of berkelium-249 with neon-22 to produce bohrium-267. Write a nuclear reaction for this synthesis. The half-life of bohrium-267 is 15.0 seconds. If... 

Plutonium is considered a transuranium (having an atomic number greater than that of uranium) element. It has a very long radiological half-life (86 and 24,000 years for plutonium-238 and -239, respectively), and, therefore, the radioactivity diminishes very slowly. Spent nuclear fuel is not reprocessed in the United States at the present time, and the fuel must be disposed of intact (Lamarsh 1983). The usual method of disposal has been to place the fuel in suitable containers and bury them in a waste repository. Prior to 1970 solid wastes containing radioactive wastes generated by nuclear power plants were buried at commercial waste sites located at Sheffield, Illinois Beatty, Nevada Morehead, Kentucky Richland, Washington and West Valley, New York. As of 1974 approximately 80 kg of plutonium was contained in this waste (Daly and Kluk 1975). 

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