Elements, artificial

Bracketed figures are for the most commonly available isotope in the case of artificial elements. 

The many possible oxidation states of the actinides up to americium make the chemistry of their compounds rather extensive and complicated. Taking plutonium as an example, it exhibits oxidation states of -E 3, -E 4, +5 and -E 6, four being the most stable oxidation state. These states are all known in solution, for example Pu" as Pu ", and Pu as PuOj. PuOl" is analogous to UO , which is the stable uranium ion in solution. Each oxidation state is characterised by a different colour, for example PuOj is pink, but change of oxidation state and disproportionation can occur very readily between the various states. The chemistry in solution is also complicated by the ease of complex formation. However, plutonium can also form compounds such as oxides, carbides, nitrides and anhydrous halides which do not involve reactions in solution. Hence for example, it forms a violet fluoride, PuFj. and a brown fluoride. Pup4 a monoxide, PuO (probably an interstitial compound), and a stable dioxide, PUO2. The dioxide was the first compound of an artificial element to be separated in a weighable amount and the first to be identified by X-ray diffraction methods. 

Gr. technetos, artificial) Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was found in a sample of molybdenum, which was bombarded by deuterons in the Berkeley cyclotron, and which E. Eawrence sent to these investigators. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial material have been made. Finally in 1962, technetium-99 was isolated and identified in African pitchblende (a uranium rich ore) in extremely minute quantities as a spontaneous fission product of uranium-238 by B.T. Kenna and P.K. Kuroda. If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars. 

Plutonium (Pu) is an artificial element of atomic number 94 that has its main radioactive isotopes at 2 °Pu and Pu. The major sources of this element arise from the manufacture and detonation of nuclear weapons and from nuclear reactors. The fallout from detonations and discharges of nuclear waste are the major sources of plutonium contamination of the environment, where it is trapped in soils and plant or animal life. Since the contamination levels are generally very low, a sensitive technique is needed to estimate its concentration. However, not only the total amount can be estimated. Measurement of the isotope ratio provides information about its likely... 

Some of the important properties of Group 7 elements are summarized in Table 24.1. Technetium is an artificial element, so its atomic weight depends on which isotope has been produced. The atomic weights of Mn and Re, however, are known with considerable accuracy. In the case of... 

Isaac Asimov here relates the story of the long quest to identify the stuff of which the universe is made. From Thales of Miletus to Seaborg of California, from alchemy to the cyclotron, from the search for the secret of turning lead into gold to the making of artificial elements, it has been a tale of follies, fakery, brilliant discoveries, and steadily building excitement... 

Back to the facts. The use of accelerators as fusion reactors first in 1940 in Berkeley (USA), later in Dubna (Russia), and then in Darmstadt (Ge-sellschaft fur Schwerionenforschung Institute for Heavy-Ion Research) allowed the expansion of the series of elements up to atomic number 116. This means that 24 artificial elements after uranium have been produced and identified. In most cases, the half-lives are extremely short and the few at-... 

Scientific chemistry has its roots in the European Enlightenment. All 92 naturally occurring elements were discovered and identified here. The map shows that England, France, and Sweden played central roles, whereas in Germany research was carried out in the various regional centers. With the advent of atomic research, the emphasis on the discovery of the artificial elements shifted to the USA. They were later joined by Russia (Dubna) and Germany (Institute for Heavy-Ion Research). 

Silvery, artificial element generated by beta decay from a plutonium isotope (239Pu). Chemically similar to gadolinium. Like Eu and Gd, Am and Cm are difficult to separate. It can be produced in kilogram amounts. The most common isotope is 244Cm with a half-life of 18.1 years. Is used for thermoelectric nuclide batteries in satellites and pacemakers. It is strongly radioactive and hence also suitable for material analysis. 

Name named after its place of discovery, Berkeley, where Ernest 0. Lawrence built the first cyclotron and where most artificial elements were discovered... 

Silver-colored, artificial element, first produced by bombarding americium with helium ions. Chemically similar to terbium. Bk begins the series of elements that are generated by bombardment of artificial elements with helium ions or neutrons. To date produced in mg amounts. Only of scientific interest. 

Silvery white, artificial element that is also generated by intensive bombardment of plutonium with neutrons. It is a strong ("hot") neutron emitter and is used in microgram quantities in nuclear medicine. This reliable neutron source is also used in industry and science (for activation analysis). 

All of the artificial elements prepared thus far are radioactive. That is, of their own accord, they break down into elements of different atomic number, often with the release of tremendous quantities of energy. A few of the first 92 elements are also radioactive. They have unstable nuclei which often shoot out particles as radiation. Radiation is the name for various rays of subatomic particles given off by radioactive elements. 

Most of the larger actinides do not exist in nature. Scientists have created them artificially in the laboratory. Neptunium was first created in 1940, but lawrencium not until 1961. While these artificial elements are interesting, they are not particularly useful because they are so costly to make and because, being very unstable, they do not last very long. 

Promethium is a silvery-white, radioactive metal that is recovered as a by-product of uranium fission. Promethium-147 is the only isotope generally available for smdy. The spectral lines of promethium can be observed in the light from a distant star in the constellation Andromeda. Even so, it is not found naturally on Earth, and scientists consider it to be an artificial element. Its melting point is 1,042°C, its boiling point is estimated at 3,000°C, and its density is 7.3 g/cm. ... 

In 1955 Albert Ghiorso and his colleagues at the University of California at Berkeley discovered the artificial element mendelevium. The scientists produced mendelevium one atom at a time, getting 17 atoms in all. Mendelevium was added to the periodic table as element number 101. 

In 1993 the Americans established to lUPAC s satisfaction that theirs was the stronger claim, and the team, headed by the veteran Albert Ghiorso, proposed a name for the new element seaborgium, after the discoverer of the first artificial element. 

The periodic table is a chart that includes all of the natural and artificial elements known in the universe. Elements are basic building blocks of matter. The periodic table is more than a list of the elements. It is also a guide and tool to understanding all chemical reactions and the materials involved in building the Earth and the universe. This book will describe the history and science behind the periodic table and take an in-depth look at all the major groups of elements. 

Taken together, these papers provide insights on the structure and cognitive content of twentieth century chemistry. They all deserve careful reading and, rather than trying to summarize them, I have organized my presentation around a number of salient issues which relate them to one another the value and status of physical evidence in chemical disciplines the relationship between the identification of an element and its production the contrast between natural and artificial elements and the disciplinary dynamics that attended all of these changes. 

The Search for Artificial Elements and the Discovery of Nuclear Fission... 

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. 

When Fermi and his co-workers reached uranium, they found several new activities, all beta emitters. After chemical tests indicated that these were neither uranium itself nor the elements just below it, Fermi proposed that the uranium nucleus had captured a neutron and begun a chain of beta decays, producing elements 93, 94, and perhaps more the first artificial elements. 

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