Beyond Uranium

The discovery of the four missing elements completes the Periodic Table through uranium. 

But this is only the start of the adventure of forging new forms of matter. The achievements which followed have been exciting triumphs over nature and have influenced profoundly the world we live in. 

Beyond uranium are the highly radioactive elements with atomic numbers higher than 92. None of them exists naturally on earth except in extremely minute quantities in one or two cases. They can be produced only by synthetic means. 

Actually, all elements heavier than lead and bismuth are radioactive and are constantly disintegrating. Eventually, lead and bismuth will be the heaviest natural elements on earth, for the heavier elements—polonium, radon, radium, actinium, thorium, protactinium, and uranium—will have disappeared at some date in the distant future. 

The present existence of these elements is one of the indications of a finite age for the earth, about five billion years according to current estimates. 

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Before it was known that elements beyond uranium were capable of existence, the heaviest known natural elements, thorium, protactinium and uranium, were placed in a sixth period of the periodic classification, corresponding to the elements hafnium, tantalum and tungsten in the preceding period. It was therefore implied that these elements were the beginning of a new, fourth transition series, with filling of the penultimate n = 6 level (just as the penultimate = 5... 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

Apart from naturally occurring elements, there are now newly made elements beyond uranium. These constitute the transuranic series. All the elements in this series are radioactive. 

In 1934 Fermi decided to bombard uranium with neutrons in an attempt to produce transuranic elements, that is, elements beyond uranium, which is number 92 in the periodic table. He thought for a while that he had succeeded, since unstable atoms were produced that did not seem to correspond to any known radioactive isotope. I le was wrong in this conjecture, but the research itself would eventually turn out to be of momentous importance both for physics and for world history, and worthy of the 1938 Nobel Pri2e in Physics. 

One of the major advances of science in the first half of this century was the synthesis of ten elements beyond uranium. Glenn T. Seaborg participated in the discovery oj most of these, a sufficient tribute to his outstanding ability as a scientist. For the first such discoveries, those of neptunium and plutonium, he shared with Professor Edwin M. McMillan the Nobel Prize in Chemistry for 1951. 

Seaborg GT, Loveland WD. 1990. The elements beyond uranium. New York John Wiley Sons, Inc. 

Neptunium - the atomic niunber is 93 and the chemical symbol is Np. The name derives from the planet Neptune (the Roman god of the sea), since it is the next outer-most planet beyond the planet uranus in the solar system and this element is the next one beyond uranium in the periodic table.lt was first synthesized by Edwin M. McMillan and Philip H. Abelson in 1940 via the nuclear reaction n, y) U P = p. The longest half-life associated with this mistable... 

Aetinide metah—includes elements with atomic numbers from 89 to 111. Also includes the transuranic elements (e.g., beyond uranium to lojLr]) and the superactinides (elements with atomic numbers 104 to 118 that are artificial, radioactive, and unstable with very short half-lives). 

G. T. Seaboig and W. D. Loveland, The Elements Beyond Uranium, Wiley-Interscience, New York, 1990. 

Seaborg, G.T. and W.D, Loveland The Elements Beyond Uranium, John Wiley Sons, New York, NY, 1990. 

The first scientific attempts to prepare the elements beyond uranium were performed by Enrico Fermi, Emilio Segre, and co-workers in Rome in 1934, shortly after the existence of the neutron was discovered. This group of investigators irradiated uranium with slow neutrons and found several radioactive products, which were thought to be due to new elements. However, detailed chemical studies by Otto Hahn and Fritz Strassman in Berlin showed these species were isotopes of the known elements created by the fission of uranium into two approximately equal parts (see Chap. 11). This discovery of nuclear fission in December of 1938 was thus a by-product of man s quest for the transuranium elements. 

Neptunium, the element beyond uranium, was named after the planet Neptune because this planet is beyond the planet Uranus for which uranium is named. 

Hofmann, Sigurd. On Beyond Uranium Journey to the End of the Periodic Table. London Taylor and Francis, 2002. 

The effort to synthesize artificial elements beyond uranium began in 1934, went on for several years with a number of apparent successes, and then came to an abrupt halt in 1938 when nuclear fission was discovered and scientists realized that they had not found a single new element in all that time - the entire four-year search for transuranium elements had in fact been the study of fission fragments. 

With this, the goals of those who first sought artificial elements beyond uranium were realized. The understanding of nuclear behavior was deepened by the discovery of nuclear fission, and the periodic system was extended and clarified by the synthesis of transuranium elements. 

Seaborg, Glenn T., and Loveland, Walter D. (1990). The Elements beyond Uranium. New York Wiley. 

Most of the chemical elements are metals and many of them are little used some are so rare that only the man-made variety exists on earth, and that applies to the radioactive elements beyond uranium, which is element number 92 in the periodic table. It is also true for lighter elements such as technetium (element 43) and promethium (element 61). Yet such elements have their uses technetium in medical diagnostics, promethium in miniature batteries for pacemakers. Hopefully, most people will never need to encounter either metal, but some radioactive metals should be a part of everyone s life and especially... 

The chemistry of actinides is more complicated due to the existence of greater range of oxidation states for these metals. Moreover, all these metals are radioactive and therefore, their accessibility for laboratory investigations is limited. The elements beyond uranium are all man-made elements and are made by nuclear-chemical methods. 

Kauffman, G., Beyond Uranium, Chemical and Engineering News, Washington, DC, Nov. 1990. 

JCKidation states in aqueous solution the predominant oxidation state is in bold face, from G.T. Seaborg and WJ>. Loveland, The etementt beyond uranium, p. 64. Wiley Intersoence, New York (1990). 

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