Promethium: the essentials
Great care is required while handling promethium as a consequence of its radioactivity. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity. Ion-exchange methods led to the preparation of about 10 g of promethium from atomic reactor fuel processing wastes in early 1963.
Little is yet generally known about the properties of metallic promethium. More than 30 promethium compounds have been prepared. Promethium is a rare earth metal. It appears that there is no known Pm existing in the earth's crust.
This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.
Promethium: historical information
Earlt claims to the discovery of promethium date back to 1924 but these appear have been substantiated. A group at Ohio State University (USA) claimed element 61 in experiments involving its synthesis in a cyclotron, but again the evidence did not satisfy everyone. In 1947, Marinsky, Glendenin, and Coryell at Oak Ridge, Tennessee, USA, made the first chemical identification of promethium by use of ion-exchange chromatography on residues in a nuclear reactor.
Promethium around us Read more »
Promethium has no biological role.
It appears that there is no known Pm existing in the earth's crust other than in very small quantities in uranium ores where it is present as a uranium decay product.
|Location||ppb by weight||ppb by atoms||Links|
|Universe||(no data)||(no data)|
|Crustal rocks||(no data)||(no data)|
|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 1373 [1100 °C (2012 °F)] K
- Boiling point: 3273 [3000 °C (5432 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of promethium is: .
Promethium: orbital properties Read more »
Promethium atoms have 61 electrons and the shell structure is 22.214.171.124.8.2. The ground state electronic configuration of neutral Promethium is [Xe].4f5.6s2 and the term symbol of Promethium is 6H5/2.
- Pauling electronegativity: (no data) (Pauling units)
- First ionisation energy: 540 kJ mol‑1
- Second ionisation energy: 1050 kJ mol‑1
Isolation: promethium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure promethium is available through the reduction of PmF3 with calcium metal.
2PmF3 + 3Ca → 2Pm + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Promethium isotopes Read more »