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| Atomic symbol: Pm |
| Atomic number: 61 |
| Atomic weight: (145) |
| Atomic volume: 22.39 cm33/mol |
| Density: 6.475 g/cm3 |
| Period Number: 6 |
| Group number: none |
| Group name: Rare Earth, Lanthanides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 1353.2 K |
| Boiling point: K |
| Heat of fusion: ? |
| Heat of vaporization: ? |
| Ionization Energy: 5.55 eV |
| 1st ionization energy: 535.9 kJ/mole |
| 2nd ionization energy: 1052 kJ/mole |
| 3rd ionization energy: 2150 kJ/mole |
| Electronegativity: 1.15 |
| Electron affinity: 50 kJ/mole |
| Specific heat: 0.18 J/gK |
| Heat atomization: 301 kJ/mole atoms |
| Shells: 2,8,18,23,8,2 |
| Electron Shell Configuration: [Xe] 4f5 6s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 3 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 3 |
Appearance & Characteristics |
| Structure:: cp: close packed (ABCB) |
| Color: silvery-white |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: Radioactive |
| Uses: nuclear battery |
| Reaction with air: vigorous, =>Pm2O3 |
| Reaction with 6M HCl: mild, =>H2, PmCl3 |
| Reaction with 15M HNO3: mild, =>Pm(NO3)3 |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 0 |
| Oxide(s): Pm2O3 |
| Hydride(s): ? |
| Chloride(s): ? |
| Atomic Radius: 183 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 111 pm |
| Thermal conductivity: 17.9 J/m-sec-deg |
| Electrical conductivity: 1/mohm-cm |
| Polarizability: 30.1 A^3 |
| Source: Synthetic |
| Relative abundance solar system: log |
| Abundance earth's crust: -19.3 log |
| Estimated crustal abundance: Not Applicable |
| Estimated oceanic abundance: Not Applicable |
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| (Gr. Prometheus, who, according to mythology, stole fire from heaven) In 1902 Branner predicted the existence of an element between neodymium and samarium, and this was confirmed by Moseley in 1914. In 1941, workers at Ohio State University irradiated neodymium and praseodymium with neutrons, deuterons, and alpha particles, and produced several new radioactivities, which most likely were those of element 61. Wu and Segre, and Bethe, in 1942, confirmed the formation; however, chemical proof of the production of element 61 was lacking because of the difficulty in separating the rare earths from each other at that time. In 1945, Marinsky, Glendenin, and Coryell made the first chemical identification by use of ion-exchange chromatography. Their work was done by fission of uranium and by neutron bombardment of neodymium. |
| 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. |
| It is a soft beta emitter; although no gamma rays are emitted, X-radiation can be generated when beta particles impinge on elements of a high atomic number, and great care must be taken in handling it. 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. Two allotropic modifications exist. |
| The element has applications as a beta source for thickness gages, and it can be absorbed by a phosphor to produce light. Light produced in this manner can be used for signs or signals that require dependable operation; it can be used as a nuclear-powered battery by capturing light in photocells which convert it into electric current. Such a battery, using 147Pm, would have a useful life of about 5 years. Promethium shows promise as a portable X-ray source, and it may become useful as a heat source to provide auxiliary power for space probes and satellites. More than 30 promethium compounds have been prepared. Most are colored. |
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