Promethium isotopes

Unter den Spaltprodukten des Urans wurden in der Promethium-fraktion mindestens vier — meist kurzlebige — Promethium-Isotope nachgewiesen Pm 147, Pm 148, Pm 149 und Pm 151. Das langlebigste unter ihnen ist das /S -instabile Pm 147, das mit einer Halbwertszeit von 2,6 Jahren gemaB... 

Das Promethium konnte als ungeradzahliges Element stabile Isotope mit der Masse 145 und 147 besitzen, die jedoch auf Grund der Mattauch-schen Isobarenregel auBer Frage stehen, so daB alle Promethium-Isotope instabil sind. Es besteht jedoch die Moglichkeit, daB noch unent-deckte Promethium-Isotope existieren, die eine langere Halbwertszeit als Pm 147 aufweisen. Hierfiir kommen hauptsachlich das Pm 145 und... 

Das Pm 146 kann jedoch nicht zur Erforschung des Promethiums dienen, da es im Vergleich zu Pm 147 nur in minimalen Mengen und nie-mals rein entstehen kann bei der Protonenbestrahlung des Neodyms treten dessen samtliche Isotope mit Protonen in (p, n)-Reaktion und liefem verschiedene Promethium-Isotope. 

The two adjacent isobars, mass numbers A = 145 and A = 147, are of the odd- ven and evar-odd types, thus only one isobaric /3-decay curve exists for each of these. The decay scheme for A = 145 follows curve I in Figure 3.6 for which d is the stable isobar. Pm is the longest lived promethium isotope (fi 17.7 y). For yl = 147, the stable isobar is g2 m the half-life of Pm is 2.62 y, wUch makes it die most convaiiait radioisotope of promethium for use in experimaits. 

But in this respect nuclear physics proved to be a foe of natural promethium. With each newly synthesized promethium isotope a possible scope for search became increasingly narrow. The promethium isotopes were found to be short-lived. Among the fifteen promethium isotopes known today the longest-lived one has a half-life of only 30 years. In other words, when Earth had just formed as a planet not a trace of promethium could exist on it. But what we mean here is the primary promethium formed in the primordial process of origination of elements. What was discussed was the search for the secondary promethium which is still being formed on Earth in various natural nuclear reactions. 

Technetium was finally found on Earth among the fragments of spontaneous fission of uranium. These fission products could contain promethium isotopes. According to estimates, the amount of promethium that can be produced owing to spontaneous fission of uranium in tbe Earth s crust is about 780 g, that is, practically, nothing. To look for natural promethium would be tantamount to dissolving a barrel of salt in the lake Baikal and then trying to find individual salt molecules. 

But this titanic task was fulfilled in 1968. A group of American scientists including the discoverer of natural technetium P. Kuroda managed to find the natural promethium isotope with a mass number of 147 in a specimen of uranium ore (pitchblende). This was the final step in the fascinating history of the discovery of element 61. 

The first date is the date of its synthesis, that is, 1945. But under the circumstances synthesis was unconventional (it could he called fission synthesis). The first two promethium isotopes were extracted from the fragrments of fission of uranium irradiated with slow neutrons rather than in a direct way as was the case with technetium, which was produced in a direct nuclear reaction. This makes promethium a unique case amonq all other synthesized elements. 

Although these promethium isotopes have much shorter half-lives than the corresponding technetium isotopes, the decay energies for promethium are actually lower. Decay of the technetium isotopes is hindered by large angular momentum changes. 

If radioactive elements disintegrate, how is it possible that they still remain in the earth s crust after 4.5 billion years, which is estimated to be the age of the earth Yet, some are not left - the exciting story about the search for element 43, technetium, tells us that (Chapter 28 Technetium). It is the same story for the rare earth element 61, promethium (Chapter 17 Rare earths). These elements may be found after reactions in a nuclear reactor, but they are short-lived. The most long-lived technetium isotope has a half-life of 4 million years the most long-lived promethium isotope only 17.7 years. If they had been present at the creation of the earth, they would have disappeared long ago. 

Searches for the element on earth have been fruitless, and it now appears that promethium is completely missing from the earth s crust. Promethium, however, has been identified in the spectrum of the star HR465 in Andromeda. This element is being formed recently near the star s surface, for no known isotope of promethium has a half-life longer than 17.7 years. Seventeen isotopes of promethium, with atomic masses from 134 to 155 are now known. Promethium-147, with a half-life of 2.6 years, is the most generally useful. Promethium-145 is the longest lived, and has a specific activity of 940 Ci/g. 

This book presents a unified treatment of the chemistry of the elements. At present 112 elements are known, though not all occur in nature of the 92 elements from hydrogen to uranium all except technetium and promethium are found on earth and technetium has been detected in some stars. To these elements a further 20 have been added by artificial nuclear syntheses in the laboratory. Why are there only 90 elements in nature Why do they have their observed abundances and why do their individual isotopes occur with the particular relative abundances observed Indeed, we must also ask to what extent these isotopic abundances commonly vary in nature, thus causing variability in atomic weights and possibly jeopardizing the classical means of determining chemical composition and structure by chemical analysis. 

Promethium (Z = 61) is essentially nonexistent in nature all of its isotopes are radioactive. Write balanced nuclear equations for the decomposition of... 

Elements 43 (technetium), 61 (promethium), 85 (astatine), and all elements with Z > 92 do not exist naturally on the Earth, because no isotopes of these elements are stable. After the discovery of nuclear reactions early in the twentieth century, scientists set out to make these missing elements. Between 1937 and 1945, the gaps were filled and three actinides, neptunium (Z = 93), plutonium (Z = 94), and americium (Z = 95) also were made. 

Wie im Abschnitt III, B (S. 754) angegeben wurde, ist das Promethium in Form von Pm 147 in Milligrammengen erhaltlich. Dies wird durch die mittlere Lebensdauer (Tj2 = 2,6 Jahre) dieses Isotops und durch den Umstand ermoglicht, daB es bei der Uranspaltung in groBer Ausbeute... 

Bei Promethium wtirde man betastabile Isotope mit den Massenzahlen 145 und 147 erwarten. Beide sind jedoch auf Grund der allge-... 

Diese Betrachtungen zeigen also, daB bei den Elementen Technetium, Promethium und Astatium betastabile Isotope nicht existieren konnen, so daB wir fur den Begriff, Luckenelemcnte folgende exakte Definition geben konnen ... 

Aus den Tabellen 16,17 und 18 ist ersichtlich, daB die ftir Betastabili-tat in Frage kommenden Isotope des Technetiums, Promethiums und Astatiums,... 

Table A. 1 comprises the stable elements from hydrogen to bismuth with the radioactive elements technetium and promethium omitted. Natural variations in isotopic composition of some elements such as carbon or lead do not allow for more accurate values, a fact also reflected in the accuracy of their relative atomic mass. However, exact masses of the isotopes are not affected by varying abundances. The isotopic masses listed may differ up to some 10 u in other publications.

ISOTOPES There are a total of 64 isotopes of promethium with half-lives ranging from two milliseconds to over 17 years. There is no stable isotope, but Pm-147 with a half-life of 2.64 years is considered the most stable. No promethium is found naturally in the Earth s crust. All of it is produced artificially from the leftover residue in nuclear reactors. 

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. ... 

Promethium is an extremely strong radiation hazard. Because it is so rare, few people wdl come in contact with it, but special precautions must be used when working with its isotopes. 

Symbol Pm atomic number 61 atomic weight 145 a lanthanide series inner-transition metal electron configuration [Xe]4/56s2 partially filled f orbitals valence states -i-3 ionic radius Pm " 0.98A aU isotopes of promethium are radioactive twenty-two isotopes in the mass range 134-155 longest-lived isotope Pm-145, ti/2 17.7 year shortest-bved isotope Pm-140, ti/2 9.2 sec. 

Promethium—147, the isotope used commercially, is isolated from fission product wastes. The radioactive materials must be handled safely in a glove box. The metal complexes either with ethlenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) and is isolated by elution from Dowex 50. 

All isotopes of promethium and their salts present radiation hazard from exposure to beta and gamma rays. 

Aft er many false reports of its occurrence in nature, promethium was finally identified in 1947 in fission productsby Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell. It was named after the Greek mythological character Prometheus who stole fire from the heavens. No stable isotopes of Pm exist, its longest lived isotope being Pm-145 (half life 17.7 years), but... 

A radioactive element is an element that disintegrates spontaneously with the emission of various rays and particles. Most commonly, the term denotes radioactive elements such as radium, radon (emanation), thorium, promethium, uranium, which occupy a definite place in the periodic table because of their atomic number. The term radioactive element is also applied to the various other nuclear species, (which arc produced by the disintegration of radium, uranium, etc.) including (he members of the uranium, actinium, thorium, and neptunium families of radioactive elements, which differ markedly in their stability, and are isotopes of elements from thallium (atomic number 81) to uranium (atomic number... 

C.A. Arrhenius, in 1787, noted an unusual black mineral in a quarry near Ytterby. Sweden, This was identified later as containing yttrium and rare-earth oxides. With the exception of promethium, all members of the Lanthanide Series had been discovered by 1907, when lutetium was isolated. In 1947. scientists at the Atomic Energy Commission at Oak Ridge National Laboratory (Tennessee) produced atomic number 61 from uranium fission products and named it promethium. No stable isotopes of promethium have been found in the earth s crust. 

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