|Name , symbol , atomic number||Promethium, Pm, 61|
|Group , period , block||La , 6 , f|
|Mass fraction of the earth's envelope||1.5 · 10 −15 ppm|
|Atomic mass||( 147 μm) 146.9151 u|
|Atomic radius (calculated)||185 (205) pm|
|Covalent radius||199 pm|
|Electron configuration||[ Xe ] 4 f 5 6 s 2|
|1. Ionization energy||5.58187 (4) eV ≈ 538.1 kJ / mol|
|2. Ionization energy||10.938 (20) eV ≈ 1 055.4 kJ / mol|
|3. Ionization energy||22nd.44 (8) eV ≈ 2 170 kJ / mol|
|4. Ionization energy||41.17 (9) eV ≈ 3 970 kJ / mol|
|5. Ionization energy||61.7 (3) eV ≈ 5 950 kJ / mol|
|density||7.2 g / cm 3 (25 ° C )|
|Melting point||1353 K (1080 ° C)|
|boiling point||3273 K (3000 ° C)|
|Molar volume||20.10 · 10 −6 m 3 · mol −1|
|Heat of evaporation||290 kJ / mol|
|Heat of fusion||7.7 kJ mol −1|
|Electric conductivity||1.33 · 10 6 A · V −1 · m −1|
|Thermal conductivity||15 W m −1 K −1|
|Normal potential||−2.423 V
(Pm 3+ + 3 e - → Pm)
|For other isotopes see list of isotopes|
|Hazard and safety information|
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .
Promethium (from Prometheus , a titan of Greek mythology ) is a chemical element with the element symbol Pm and the ordinal number 61. In the periodic table it is in the group of lanthanoids and is therefore also one of the rare earth metals . Promethium was discovered in 1945 as a fission product of uranium. His discovery closed the last gap in the periodic table.
All promethium isotopes are radioactive , which means that all atomic nuclei that contain 61 protons are unstable and decay. Promethium and the lighter technetium (43) are the only elements with a smaller atomic number than bismuth (83) that have this property.
For the first time a discovery was reported by the Italian scientists Luigi Rolla and Lorenzo Fernandes from Florence. After separating a didymium nitrate concentrate by fractional crystallization from the Brazilian mineral monazite , which consists of 70% dysprosium and neodymium and 30% of the other lanthanoids, they received a solution that mainly contained samarium. This solution resulted in X-ray spectra which they interpreted as samarium and element 61. They named element 61 in honor of their city, Florentium . The results were published in 1926, but the scientists claimed that the experiments were carried out in 1924.
In the same year 1926, Smith Hopkins and Len Yntema at the University of Illinois at Urbana-Champaign also published the discovery of element 61. They named it after the University of Illinois .
Neither of the two publications could be confirmed. Several groups claimed to have created the element, but verification of their discoveries failed due to the difficulty in separating promethium from the other elements.
Evidence by Marinsky, Glendenin and Coryell
Promethium was discovered in 1945 in the Oak Ridge National Laboratory (ORNL) ( Tennessee , USA ) by Jacob A. Marinsky , Lawrence E. Glendenin and Charles D. Coryell as a fission product of uranium . Due to military research during World War II, its discovery was not published until 1947. They chose the name Promethium based on the Greek titan Prometheus, who brought fire to humans and thus aroused the wrath of the gods. This was intended as a warning to humankind, who at that point were beginning the nuclear arms race . The name was suggested by Grace Mary Coryell, Charles Coryell's wife.
In nature, promethium is mostly found as a product of the spontaneous fission of uranium and through alpha decay of the europium isotope 151 Eu. It is found in traces in pitchblende in a concentration of (4 ± 1) · 10 −15 grams 147 μm per kg. The even occurrence of promethium in the earth's crust is about 560 g due to uranium fission and about 12 g due to alpha decay of 151 Eu.
- Spontaneous fission of uranium:
- Alpha decay of 151 Eu:
Extraction and presentation
In 1963, ion exchange methods were used in the ORNL to obtain approximately 10 grams of promethium from nuclear reactor fuel waste. In 1963 Fritz Weigel was able to produce metallic promethium for the first time by heating promethium (III) fluoride (PmF 3 ) with lithium in a tantalum crucible.
In the periodic table , the promethium with the atomic number 61 is in the series of the lanthanoids, its predecessor is neodymium , the following element is the samarium . Its analogue in the actinoid series is the neptunium .
Since the isotope 147 μm can be obtained artificially as a fission product in weighable quantities, it is possible to investigate the properties quite well. Promethium is a silvery white ductile heavy metal. It has a melting point of 1080 ° C; for the boiling point there are estimated values of 2727 and 3000 ° C. Under standard conditions, promethium crystallizes in a hexagonal closest packing of spheres with the lattice parameters a = 365 pm and c = 1165 pm with a calculated density of 7.26 g / cm 3 .
The metal is oxidized very quickly in air and reacts slowly with water. Promethium occurs in its compounds only in the +3 oxidation state ([Xe] 4f 4 ). It releases the two 6s electrons and one 4f electron. The solutions are purple-tinged pink in color. Among other things, it forms a sparingly soluble fluoride , oxalate and carbonate .
The most stable isotope is 145 μm with a half-life of 17.7 years, followed by 146 μm with a half-life of 5.53 years and 147 μm with a half-life of 2.6234 years. The latter is mostly used for investigation, as it is produced in sufficient quantities as a cleavage product .
Due to the short-lived isotopes and the very low availability, this element is only used in small quantities for technical purposes. The most important application is as a beta emitter.
The element is a possible mobile source of X-rays that is used for radiometric thickness measurement.
The nuclide 147 μm served not only as a beta radiation source but also as an additive for luminous paint , which was used in luminous numerals of watches and the target optics of weapons such as the M72 (LAW) .
→ Category: Promethium compound
Promethium (III) oxide (Pm 2 O 3 ) has three different modifications: a hexagonal A-shape (violet-brown), a monoclinic B-shape (violet-pink) and a cubic C-shape (coral red). The melting point is 2130 ° C.
All halides from fluorine to iodine are known to have an oxidation state of +3.
Promethium (III) fluoride (PmF 3 ) is sparingly soluble in water; it is obtained from a Pm 3+ nitric acid solution by adding HF solution; the precipitate has a pale pink color. Crystalline anhydrous promethium (III) fluoride is a purple-pink salt with a melting point of 1338 ° C.
Promethium (III) iodide (PmI 3 ) cannot be prepared from Pm 2 O 3 by reaction with HI - H 2 mixtures; instead, promethium (III) oxyiodide (PmOI) is formed. The desired product is formed by reaction of Pm 2 O 3 with molten aluminum iodide (AlI 3 ) at 500 ° C. It's red and has a melting point of 695 ° C.
Promethium (III) hydroxide (Pm (OH) 3 ) is obtained from a hydrochloric acid Pm 3+ solution by introducing NH 3 . Its color is purple pink.
Classifications according to the CLP regulation are not available because they only include chemical hazard and play a completely subordinate role compared to the hazards based on radioactivity . The latter also only applies if the amount of substance involved is relevant.
- Fritz Weigel: Chemistry of Promethium , in: Fortschr. Chem. Forsch. , 1969 , 12 (4), pp. 539-621 ( doi: 10.1007 / BFb0051097 ).
Gmelin's Handbook of Inorganic Chemistry , System No. 39:
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- Part B 2, pp. 46, 94-96, 149, 215
- Part B 3, pp. 69, 74-75
- Part B 5, pp. 131-145
- Part B 6, pp. 131-133, 156, 160
- Part B 7, p. 193
- Part C 1, pp. 312-313
- Part C 2, pp. 56-57, 261
- Part C 3, pp. 194, 257
- Part C 4 b, pp. 181-183
- Part C 5, p. 31
- Part C 6, pp. 61-62, 192
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- The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
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