Elements man-made

G. T. Seaborg (ed.), Transuranium Elements Products of Modem Alchemy, Dowden, Hutchinson Ross, Stroudsburg, 1978. This reproduces, in their original form, 122 key papers in the story of man-made elements. 

Chromium in the crystalline form is a steel-gray, lustrous, hard metal characterized by an atomic weight of 51.996, an atomic number of 24, a density of 7.14 g/cm3, a melting point of 1857°C, and a boiling point of 2672 C. Four chromium isotopes occur naturally Cr-50 (4.3%), -52 (83.8%), -53 (9.6%), and -54 (2.4%), and seven are man-made. Elemental chromium is very stable but is not usually found pure in nature. Chromium can exist in oxidation states ranging from -2 to +6, but is most frequently found in the environment in the trivalent (+3) and hexavalent (+6) oxidation states. The +3 and +6 forms are the most important because the +2, +4, and +5 forms are unstable and are rapidly converted to +3, which in turn is oxidized to +6 (Towill et al. 1978 Langard and Norseth 1979 Ecological Analysts 1981 USPHS 1993). 

Introduction.—The identification of technetium in stars has been confirmed, thus establishing that stellar synthesis of this element is occurring. Recent developments in the analytical chemistries of technetium and rhenium have been reviewed, as has the extraction of rhenium from hydrochloric acid solutions a text describing the analytical chemistry of technetium and other man-made elements has been published. ... 

Italian scientists Emilio Segre and Carlo Perrier Discovered when molybdenum was bombarded with the nuclei of a hydrogen isotope the first man-made element, hence its name, which means artificial in Greek. 

Symbol Am Atomic Number 95 Atomic Weight 243.0614 an inner-transition, actinide series, radioactive man-made element electron configuration ... 

Americium does not occur in nature. It is a man-made element produced in nuclear reactors. 

Radioactive elements are ones in which the atoms break up, changing into atoms of other elements. The time taken for half the original element to disappear is called the half-life. The man-made element fermium has a half-life of 80 days. Thus, if a gramme of fermium were made today, less than one-sixteenth of a gramme would be left at the end of a year. The half-life can be very useful. By measuring the amount of radioactive carbon left in fossil remains, or other matter that was once alive, scientists can determine their age. 

The purpose of this paper is to compare the biogeochemical behavior of the actinides which are important constituents of nuclear fuel cycles. To the extent possible, the environmental behavior of the essentially man-made elements Pu, Am, Cm and Np will be compared to Th and U, which are ubiquitous in the environment. By comparing the man-made actinides to naturally occurring actinides, a generic perspective of the potential hazard of the synthetic actinides to people is obtainable. 

The behaviour of technetium in the geosphere is of particular importance in nuclear fuel waste management studies because this man-made element has a long half-life and, under ambient conditions in the laboratory, is not readily sorbed on geologic materials. 

Plutonium is a man-made element, and only infinitesimal traces occur naturally. It melts at 641°C and boils at 3330°C. 239Pu is formed in nuclear reactors by neutron capture in 238U, followed by two successive beta decays (Fig. 5.1). Further neutron captures lead to 240Pu and 241 Pu. 238Pu is formed from 239Pu by (n,2n) reactions, or from 235U by three successive neutron captures and two beta decays. Table 5.1 shows the half-lives, alpha and X-ray energies of the principal Pu isotopes. 

Artificial radioactivity The spontaneous emission of radiations by many man-made elements, which are radioactive is called artificial radioactivity. 

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. 

Certain of the transplutonium elements are used extensively in nuclear gauges and in many other fields as well. Industrial-scale production of these man-made elements requires development and application of appropriate recovery, separation, and purification processes. 

This collection of the state-of-the-art papers emphasizes the continuing importance of industrial-scale production, separation, and recovery of transplutonium elements. Americium (At. No. 95) and curium (At. No. 96) were first isolated in weighable amounts during and immediately after World War II. Berkelium and californium were isolated in 1958 and einsteinium in 1961. These five man-made elements, in each case, subsequently became available in increasing quantities. 

Of the 106 or so natural and man-made elements, less than 20% are non-metals. At present, few of the metals are used to any large extent by man, either because of their rarity or their instability. The major "tonnage metals are iron, copper, aluminium, zinc, nickel, and lead. These metals may be alloyed with one another, such as copper and zinc to form brass, and/or may be alloyed with smaller quantities of other metals. Steels are commonly alloyed with chromium, vanadium, molybdenum, or tungsten. Aluminium, for increased lightness and strength, may be alloyed with magnesium. 

Activation Production of radionuclides by nuclear reactions Artificial elements Man-made elements produced by nuclear reactions Autoradiography Picture produced by nuclear radiation in photographic films or plates... 

Plutonium— A man-made element that is created from uranium-238 by neutron bombardment and can be used as a material for fission energy. Radioactive waste—The radioactive fragments produced by fission, which accumulate in the fuel rods of a nuclear reactor and eventually must be removed. 

The lanthanide series of metals includes the 15 elements with atomic numbers 57-71, plus yttrium (atomic number 39). The lanthanides occur in the earth s crust at concentrations exceeding some commonly used industrial elements making the term rare earths something of a misnomer. For example, yttrium, cerium, lanthanum, and neodymium are present in the earth s crust at higher concentrations than lead. Of the 15 lanthanides, only promethium does not occur in nature - it is a man-made element. All of the lanthanides have similar physical and chemical properties. Because of similarities in their chemistry and toxicity, the characteristics of the lanthanides are often described as a group. Within the lanthanide group, however, there are differences between the toxicity of the individual lanthanide elements and their compounds. 

The cyclotron has been a key instrument in the production and discovery of synthetic, man-made elements. 

But the story of the man-made elements really begins in 1925 when the last of the eighty-eight natural elements was discovered. In one sense, the Periodic Table was complete at this time, as shown on page 85. 

This was the first man-made element, and for this reason we called it technetium, which means artificial. In this work Carlo Perrier, who was a mineralogist, helped me, and the problem was quite natural for a mineralogist because, at least with respect to effort, it was similar to digging an ore out of a mine. 

AAy message today is in the field of shelter—shelter from those relatively new man-made elements of hazard and destruction. 

The transuranium elements (Z > 93) are almost exclusively all man-made. Other man-made elements include technetium (Tc), promethium (Pm), astatine (At) and francium (Fr). 

Q1, Americium Am at. wt (most stable isotope) 243 at no. 95 valence 3 4, 5, 6, Completely man-made element. Isotopes (mass numbers) 237-246 all are radioactive, First isotope prepared (Tw 458 years a-emit ... 

Plutonium (chemical symbol Pu) is a radioactive metal with Atomic Number 94, Plutonium is considered a man-made element, although scientists have found trace amounts of naturally occurring plutonium produced under highly unusual geologic circumstances. The most common radioisotopes of plutonium are plutonium-238, plutonium-239, and plutonium-240. 

Actually, we can make a lot of elements synthetically. Here s a list of all of the man-made elements ... 

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