Promethium, Pm, Atomic number 61


Promethium (von Prometheus, a Titan in Greek mythology) is a chemical element with the element symbol Pm and atomic number 61. In the periodic table it is in the group of lanthanides and is thus also one of the rare earth metals.
Alle Promethium-Isotope sind radioaktiv, that is, all nuclei, the 61 Protons contained, are unstable and decompose. Promethium and technetium the lighter (43) are the only elements with smaller atomic number than lead (82), this property have.
The first discovery was published by Italian scientists Luigi Rolla and Lorenzo Fernandes from Florence. After the separation of didymium nitrate concentrate by fractional crystallization from the Brazilian mineral monazite, to which 70 % Dysprosium and neodymium as well as to 30 % consists of the other lanthanides, they were given a solution, mainly containing samarium. This solution gave X-ray spectra, them as elements samarium and 61 interpreted. They named the element 61 in honor of their city Florentium. The results were in 1926 published, But the scientists claimed, that the experiments in 1924 been carried out are.
In the same year 1926 published and Len Smith Hopkins at Yntema University of Illinois at Urbana-Champaign, the discovery of the element 61. They called for the University Illinium.
Neither of these discoveries could be verified. Several groups have alleged, generates the element to have, but they could not confirm their discoveries because of the difficulty of separating promethium from other elements.


There are no exact knowledge of Seperierung of promethium.

Special features

Promethium wurde 1945 im Oak Ridge National Laboratory (Tennessee, USA) Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell was a cleavage product of the uranium deal entdeckt.Da it largely with military research during World War II, their discovery was first 1947 published. The name promethium they chose based on the Greek Titan Prometheus, The man brought the fire and so aroused the anger of the gods. This was meant as a warning to humanity, which began at this time with the nuclear arms race. The name was Grace Mary Coryell, Charles Frau Coryells, proposed.
In 1963 ion exchange methods were used in the ORNL, by about 10 Grams of promethium from the waste fuel from nuclear reactors could be erhalten.1963 Fritz Weigel first metallic promethium promethium by heating(III)-fluoride (PmF3) produced by lithium in tantalum crucibles.
In nature, promethium is mostly a product of spontaneous fission of uranium, as well as alpha decay of 151Eu Europiumisotops. Traces are found in pitchblende at a concentration of (4±1)·10−15 Gramm 147Pm pro kg. The uniform presence of promethium in the earth's crust is about 560 g of uranium fission and about 12 g by alpha decay of promethium was 151Eu.Auch in the emission spectrum of the star GY Andromedae demonstrated; and possibly in HD 101065 (Przybylski's star) and HD 965.
Since the isotope can be artificially produced as a fission product 147Pm in weighable quantities, it is possible, to investigate the properties very well. As a metal it is a typical representative of the lanthanides. The silver-white, relatively soft metal is oxidized in air very quickly and reacts slowly with water.
Promethium is only in its compounds in the oxidation state +3 before ([Car] 4f4). It gives off the two 6s electrons and one 4f electron. The solutions are colored violet shade pink. It provides, inter alia, a sparingly soluble fluoride, Oxalate and carbonate. Promethium(III)-oxide (Pm2O3) has three different modifications: a hexagonal A-form (violettbraun), a monoclinic B form (violettrosa) and a cubic C-shape (coral). The melting point is 2130 ° C
All halides from fluorine to iodine for the oxidation state +3 known.
Promethium(III)-fluoride (PmF3) is schwerlöIIIch in water; It is obtained from a nitric acid Pm3 solution by adding HF solution, the precipitate has a pale pink color. The melting point of the anhydrous compound is 1338 ° C. If PmF3·x H2O heated, then arises promethium(III)-oxifluorid (PmOF), which is colored purple pink.
Promethium(III)-chloride (PmCl3) is violet and has a melting point of 655 ° C. PmCl3 is heated in the presence of H2O, we obtain the pale pink colored promethium(III)-oxichlorid (PmOCl).
Promethium(III)-bromide (PmBr3) arises from Pm2O3 by heating in a dry stream of HBr. It is red and has a melting point of 660 ° C.
Promethium(III)-iodide (PmI3) is not represented by the reaction of Pm2O3 with HI-H2 mixtures, is formed instead promethium(III)-oxiiodid (PmOI). By reacting with molten Pm2O3 AlI3 at 500 ° C produced the desired product. It is red and has a melting point of 695 ° C.
Promethium(III)-hydroxide (Pm(OH)3) is obtained from a hydrochloric acid solution by introducing Pm3 NH3. Its color is purple pink.
Classifications of hazardous substance regulation does not lie, because they include only the hazardous chemical, and play a completely subordinate role compared to the radioactivity of the resulting dangers. Even the latter applies only, if there is a lot of material relevant to.


Due to the short-lived isotopes and the very limited availability of this element is only in very small quantities of industrial use. The nuclides are 146Pm and 147Pm used as a stimulating beta emitters in luminous numerals of watches and cold light sources of signal systems.
In addition, the beta radiation of promethium for thickness measurement and radiometric level measurement used.
In the small space be used with radionuclide promethium.

Name, Symbol

Atomic number

Promethium, Pm, 61
Series Lanthanides
group, Period, Block The, 6, f
Appearance metallic
CAS-Nummer 7440-12-2
Mass fraction of element 1,1 ppm
Atomic mass 164,93032 you
Atomradius 175 pm
Kovalenter Radius 192 pm
Elektronenkonf. [Car] 4f(11) 6s2
1. Ionization 581,0 KJ / mol
2. Ionization 1170 KJ / mol
3. Ionization 2204 KJ / mol
Physical State fixed
Crystal structure hexagonal
Density 8,78 g/cm3 (25 ° C)
Magnetism paramagnetisch (χm = 0,049)
Melting point 1734 K (1431 C)
Boiling point 2993 K (2720 C)
Molar Volume 18,74 * 10(-6)m(3)/mol
Heat of vaporization 265 KJ / mol
Schmelzwärme 17,0 KJ / mol
Electrical conductivity 1,23*10(6) A/(V * m)
Thermal conductivity 16 W /(m*K)
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