Promethium

{ syn. }

In traces

{ syn. }

Promethium (of 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 also making it one of the metals of the rare earths. Promethium was discovered in 1945 as a fission product of uranium. The final gap was closed in the periodic table by his discovery.

All promethium isotopes are radioactive, which means that all atomic nuclei contain 61 protons are unstable and decay. Promethium and the lighter technetium (43 ) are the only elements with smaller atomic number than bismuth ( 83) have this property.

2.1 earthly occurrences
2.2 Extraterrestrial occurrences

4.1 Physical Properties
4.2 Chemical Properties

7.1 oxides
7.2 halides
7.3 Other compounds

History

Failed discoveries

The first discovery was published by the Italian scientists Luigi Rolla and Lorenzo Fernandes from Florence. After the separation of a Didym nitrate concentrate by fractional crystallization from the Brazilian mineral monazite, which is 70% dysprosium and neodymium, and 30% of other rare earths, they received a solution containing mostly samarium. This solution gave X-ray spectra, which they interpreted as samarium and element 61. They named the element 61 in honor of their city Florentium. The results were published in 1926, but scientists claimed that the experiments were carried out in 1924.

In the same 1926 Smith Hopkins and Len Yntema published at the University of Illinois at Urbana -Champaign, the discovery of element 61 They named it after the University illinium.

Neither findings could be checked. Thus, several groups claimed to have created the element, but they could not confirm their discoveries because of the difficulties in separating promethium from the other elements.

Detection by Marinsky, Glendenin and Coryell

Promethium was discovered in 1945 at Oak Ridge National Laboratory ( ORNL ), Tennessee (USA ) by Jacob A. Marinsky, Lawrence E. and Charles D. Coryell Glendenin as a fission product of uranium. Due to the military research during World War II, their discovery until 1947 was published. The name promethium they chose based on the Greek Titan Prometheus, who brought fire to humans and so aroused the wrath of the gods. This was intended as a warning to mankind that began at this time with the nuclear arms race. The name was suggested by Grace Mary Coryell, Charles Coryell's wife.

Lawrence E. Glendenin

Charles D. Coryell

Occurrence

Earthly occurrences

In nature, promethium is mostly a product of the spontaneous fission of uranium and by alpha decay of 151Eu Europiumisotops. In traces it is found in pitchblende at a concentration of ( 4 ± 1) × 10-15 grams per kg 147Pm. The uniform presence of promethium in the earth's crust is about 560 g by uranium fission and about 12 g by alpha decay of 151Eu.

Spontaneous fission of uranium:

Alpha decay of 151Eu:

Extraterrestrial occurrences

Promethium was detected in 1971 in the spectrum of the star HR 465 ( GY Andromedae ); and possibly in HD 101065 ( Przybylski 's star ) and HD 965

Production and representation

In 1963, ion exchange methods have been used in the ORNL to obtain about 10 grams of the fuel waste promethium of nuclear reactors. 1963 Fritz Weigel was first produced with lithium in the tantalum crucible metallic promethium by heating promethium (III ) fluoride ( PMF3 ).

Properties

In the periodic table the promethium is consistent with the atomic number 61 in the series of lanthanides, its predecessor is the neodymium, the subsequent element is the samarium. Its analogue in the series of actinides is the neptunium.

Physical Properties

Since the isotope 147Pm can be obtained artificially as a cleavage product in ponderable quantities, it is possible to investigate the properties quite well. Promethium is a silver-white ductile heavy metal. It has a melting point of 1080 ° C; for the boiling point, there are estimates of 2727 and 3000 ° C. Under standard conditions, promethium crystallized in a hexagonal closest packing of spheres with lattice parameters a = 365 pm and c = 1165 pm with a calculated density of 7.26 g/cm3.

Chemical Properties

The metal is oxidized quite rapidly in air and reacts slowly with water. Promethium comes in its compounds only in the oxidation state 3 ( [ Xe] 4f4 ). It gives off the two 6s electrons and one 4f electron. The solutions are colored pink with a violet tint. It is among other things a sparingly soluble fluoride, oxalate and carbonate.

Isotopes

The stable isotope is 145Pm with a half-life of 17.7 years, it follows 146Pm with a half-life of 5.53 years and with 2.6234 147Pm years. The latter is mostly used for the investigation because it is produced in sufficient quantities as a fission product.

Use

Due to the short-lived isotopes and the very low availability of this element is technical use only in small quantities. The most important use is as a beta emitter. Promethium is used in radionuclide batteries that are used in space about as heat and energy source in satellites. The element is a possible source for mobile X-ray radiation which is used for the radiometric measurement of the thickness.

The nuclide 147Pm used except as a beta radiation source as an additive for light color that is used in luminescent numerals of watches.

Compounds

→ Category: Promethiumverbindung

Oxides

Promethium (III ) oxide ( Pm2O3 ) has three different modifications: a hexagonal A- form ( purple-brown ), a monoclinic B-form (violet pink) and a cubic C- form ( coral ). The melting point is 2130 ° C.

Halides

All halides of fluorine to iodine are known for the oxidation state 3.

Promethium (III ) fluoride ( PMF3 ) is sparingly soluble in water; to get it from a nitric acid Pm3 solution by adding HF solution, and 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 ) chloride ( PmCl3 ) is purple and has a melting point of 655 ° C. If PmCl3 heated in the presence of H2O, so you get the pale pink colored promethium (III ) oxychloride ( PmOCl ).

Promethium (III ) bromide ( PmBr3 ) gives Pm2O3 by heating in dry HBr stream. It is red and has a melting point of 660 ° C.

Promethium (III ) iodide ( PmI3 ) is not feasible from the Pm2O3 by reaction with HI -H2 mixtures, it forms instead promethium (III) oxiiodid (PMOI ). By reacting with molten aluminum iodide Pm2O3 ( AlI3 ) at 500 ° C, the desired product. It is red and has a melting point of 695 ° C.

Safety

Classifications according to the Hazardous Substances Ordinance are not available because they only include the chemical danger and play a very minor role compared to the risks based on the radioactivity. Even the latter applies only if there is a relevant material for this amount.

Beryllium Sodium Magnesium Aluminium Chlorine Argon Titanium Chromium Manganese Cobalt Nickel Zinc Germanium Arsenic Selenium Bromine Rubidium Yttrium Zirconium Ruthenium Palladium Cadmium Indium Antimony Tellurium Barium Lanthanum Praseodymium Gadolinium Terbium Holmium Erbium Thulium Tungsten Rhenium Osmium Iridium Lead Polonium Astatine Francium Radium Actinium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Dubnium Bohrium Darmstadtium Copernicium Group (periodic table) Period (periodic table) Block (periodic table) Period 6 element CAS registry number Covalent radius Decay energy Rare earth element Atomic nucleus Didymium Uraninite Structural analog Nuclear fission product Luminous paint Hydrogen bromide Hazardous Substances and New Organisms Act 1996 Digital Object Identifier Naturwissenschaften Astronomy and Astrophysics Gmelin database CRC Handbook of Chemistry and Physics Integrated Authority File

338398