Transuranium Elements Neptunium

This changing pattern is hy no means random, all the breakthroughs and failures had their quite ohjective causes. They will be apparent when we discuss syntheses of transuranium elements one by one starting from the first one, neptunium. 

Of course, Fermi never presented the Queen of Italy with a test-tube containing a salt of the first transuranium element. It is no more than a typical newspapermen s copy. But it is true that Fermi had in his hands element 93 though it could not be proved at the time. In his experiments the uranium target consisted of two isotopes, namely, uranium-238 and uranium-235. The latter underwent fission under the effect of slow neutrons giving rise to fragments which were the nuclei of the elements belonging to the central part of the periodic system. They greatly complicated the chemical situation but this was understood only when fission was discovered. 

But uranium-238 absorbed neutrons converting into uranium-239, a new isotope of uranium. This beta-active isotope gave rise to an isotope of the first transuranium element with an atomic number of 93. This was just what Fermi and his group thought. But the future neptunium was hard to distinguish among the multitude of fragments. This is why the experiments in mid-thirties yielded no results. 

The discovery of Hahn and Strassmann decisively stimulated actual synthesis of transuranium elements. To start, a reliable technique was needed for detection of the atoms of element 93 in a mass of fission fragments. As the masses of these fragments were comparatively small they had to travel longer distances (had longer paths) than the atoms of element 93 with a large mass. 

Thus went the argument of E. McMillan, an American physicist from the University of California. Back in the spring of 1939 he started to analyse the distribution of uranium fission fragments along their paths. He managed to obtain a sample of fragments whose path was very short and in this sample he found traces of a radioactive substance with a half-life of 2.3 days and a high radiation intensity. 

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Edwin McMillan and Philip Abelson obtain the first transuranium element, neptunium (element 93), by bombardment of uranium with neutrons. 

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. 

Especially interesting in a discussion of radionuclide speciation is the behaviour of the transuranium elements neptunium, plutonium, americium and curium. These form part of the actinide series of elements which resemble the lanthanides in that electrons are progressively added to the 5f instead of the 4f orbital electron shell. The effective shielding of these 5f electrons is less than for the 4f electrons of the lanthanides and the differences in energy between adjacent shells is also smaller, with the result that the actinide elements tend to display more complex chemical properties than the lanthanides, especially in relation to their oxidation-reduction behaviour (Bagnall, 1972). The effect is especially noticeable in the case of uranium, neptunium and plutonium, the last of which has the unique feature that four oxidation states Pum, Pu, Puv and Pu are... 

This process has been used to produce countless isotopes, including many radioactive isotopes. In addition, it has allowed scientists to produce elements with atomic numbers that are higher than that of the largest naturally occurring element, uranium. These elements are known as transuranium elements. In 1940, E. M. McMillan and P. H. Abelson of the University of California, Berkeley produced the first transuranium element, neptunium (Np, Z=93), by bombarding uranium-238 with neutrons. The nuclei that captured the neutrons were converted to uranium-239, which decayed into neptunium-239 during a beta emission. The reaction is shown below ... 

The first transuranium element, neptunium (Z — 93), was discovered by McMillan and Abelson in 1940 while investigating the fission products of uranium. The neptunium isotope first to be identified was Np produced by the reaction... 

In 1940, American physicists Edwin McMillan (1907—1991) and Philip Abelson (1913—2004) discovered the first transuranium element, neptunium (atomic number 93). The neptunium they produced was radioactive. They predicted it would break down to form a new element, atomic number 94. But McMillan and Abelson were called away to do research on the atomic bomb. They suggested to a colleague, Glenn Seaborg (1912-1999), that he continue their research on neptunium. 

E. M. McMillan (1907-1991) discovered the first transuranium element, neptunium, in 1940 by bombarding uranium-238 with slow neutrons. 

The first transuranium elements, neptunium and plutonium, were obtained in tracer amounts from bombardments of uranium by McMillan and Abelson and by Seaborg, McMillan, Kennedy, and Wahl, respectively, in 1940. Both elements are obtained in substantial quantities from the uranium fuel elements of nuclear reactors. Only plutonium is normally recovered and is used as a nuclear fuel since, like 235U, it undergoes fission its nuclear properties apparently preclude its use in hydrogen bombs. Certain isotopes of the heavier elements are made by successive neutron capture in 239Pu in high-flux nuclear reactors (> 1015 neutrons cm-2 sec- ). Others are made by the action of accelerated heavy ions of B, C, N, O or Ne on Pu, Am or Cm. 

The true stars of Seaborg s 1944 Periodic Table are the transuranium elements neptunium (Np) and plutonium (Pu) as well as elements 89 to 92 (actinium, thorium, protactinium, and uranium). Neptunium was synthesized by McMillan and Abelson at Berkeley in 1940. In late 1940 and early 1941 McMillan, Kennedy, Wahl, and Seaborg made Pu through bombardment of uranium with deuterons in early 1941, and Pu was obtained by bombarding uranium with neutrons. It was Seaborg who, m 1944, proposed a new series of compounds for the Periodic Table—the actinides—analogous to the rare earths or lanthanides. In his book The Periodic Kingdom, Atkins describes the lanthanides... 

Though the first transuranium element, neptunium, (No. 93) was born not so long ago, in 1940, the question about possible existence of such elements was raised much earlier. Mendeleev did not ignore it either. He believed that even if the transuranium elements would be found on Earth their number will be limited. This was his opinion in 1870. For more than 25 years the problem remained open. Every year saw several erroneous reports on discoveries of new elements but not once the element in question had an atomic mass greater than that of uranium. It seemed axiomatic that uranium was the last element in the periodic system though nobody could say why. 

The first man-made transuranium element, neptunium (Np), was discovered by McMillan and Abelson (1940) while studying the neutron-induced fission of uranium (U). The reaction used... 

The first transuranium element, neptunium, was discovered in 1940 by E. M. McMillan and P. H. Abelson. They were able to chemically separate and identify element 93 formed in the following reaction sequences [Eq. (4)] ... 

AH the elements beyond uranium, the transuranium elements, have been prepared by bombardment and are not naturally occurring elements. The first transuranium element neptunium, Np, was prepared by bombarding U-238 with neutrons to form a neptunium atom and a beta particle. Complete the following equation (16.2)... 

Edwin M. McMillan and Phillip H. Abelson succeeded in synthesizing the first transuranium element, neptunium (element 93), at the University of California, Berkeley, in 1940. In 1941, Glenn T. Seaborg synthesized and identified element 94 (plutonium), and over the next several years, researchers under his direction at UC Berkeley discovered nine other transuranium elements. In 1945 Seaborg suggested that the elements heavier than element 89 (actinium) were misplaced as transition metals and should be relocated on the periodic table in a series below the transition metals... 

Planet pluto) Plutonium was the second transuranium element of the actinide series to be discovered. The isotope 238pu was produced in 1940 by Seaborg, McMillan, Kennedy, and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California. Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural uranium with the neutrons which are present. 

Because of the high rate of emission of alpha particles and the element being specifically absorbed on bone the surface and collected in the liver, plutonium, as well as all of the other transuranium elements except neptunium, are radiological poisons and must be handled with very special equipment and precautions. Plutonium is a very dangerous radiological hazard. Precautions must also be taken to prevent the unintentional formulation of a critical mass. Plutonium in liquid solution is more likely to become critical than solid plutonium. The shape of the mass must also be considered where criticality is concerned. 

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. 

Plutonium is the second transuranium element after neptunium. The element was named after the planet Pluto. 

MCMILLAN, EDWIN M. (1907-1991). An American physicist who won the Nobel prize in chemistry in 1951 along with Glenn T. Seaborg lor their discoveries In the chemistry of the transuranium elements. His work included research in nuclear physics and particle accelerator development as well as microwave radar and sonar. He and his colleagues discovered neptunium and plutonium. He was the recipient of the Atoms for Peace prize in 1963. His Ph D. in Physics was awarded from Princeton University. 

TRANSURANIUM ELEMENTS. The chemical elements widi an atomic number higher than 92 (uranium), commencing with 93 (neptunium) and through 110 (darmstadtium) frequendy are termed Transuranium elements, Any additional elements that may be identified will be a part of this series, See also Actinide Contraction and Chemical Elements. 

Zhu, Y., Song, C. 1992. Recovery of neptunium, plutonium and americium from highly active waste. Tri-alkyl phosphine oxide extraction. In Transuranium Elements A Half Century. Morss, L.R. Fuger, J., Eds. ACS, Washington, DC, pp. 318-330. 

The actinides include another part of the periodic table called the transuranium elements, which begin with neptunium (atomic number 93) and end with roentgenium (atomic number 111) back up in Period 7. Neptunium and plutonium are the only... 

Prior to 1939, elements of atomic number greater than 92 were unknown, and there was considerable doubt as to whether such elements could exist. In 1939, however, Edwin McMillan and Philip Abel-son reported the production of the first of the transuranium elements. By bombarding uranium with neutrons, they produced an element of atomic number 93, which was later named neptunium (Np). 

E. Segre, A Mind Always in Motion The Autobiography of Emilio Segre (Berkeley, 1993), 152-153 Abelson, Discovery of Neptunium, in L. R. Morss and J. Fuger (eds.), Transuranium Elements, 53-55. 

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