Promethium
| Promethium | ||||||||||||||||||||||||||||||
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| Pronunciation | /proʊˈmiːθiəm/ | |||||||||||||||||||||||||||||
| Appearance | metallic | |||||||||||||||||||||||||||||
| Mass number | [145] | |||||||||||||||||||||||||||||
| Promethium in the periodic table | ||||||||||||||||||||||||||||||
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| Atomic number (Z) | 61 | |||||||||||||||||||||||||||||
| Group | f-block groups (no number) | |||||||||||||||||||||||||||||
| Period | period 6 | |||||||||||||||||||||||||||||
| Block | f-block | |||||||||||||||||||||||||||||
| Electron configuration | [Xe] 4f5 6s2 | |||||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 23, 8, 2 | |||||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||||
| Phase at STP | solid | |||||||||||||||||||||||||||||
| Melting point | 1315 K (1042 °C, 1908 °F) | |||||||||||||||||||||||||||||
| Boiling point | 3273 K (3000 °C, 5432 °F) | |||||||||||||||||||||||||||||
| Density (at 20° C) | α-145Pm: 7.149 g/cm3 α-147Pm: 7.247 g/cm3 [1] | |||||||||||||||||||||||||||||
| Heat of fusion | 7.13 kJ/mol | |||||||||||||||||||||||||||||
| Heat of vaporization | 289 kJ/mol | |||||||||||||||||||||||||||||
| Atomic properties | ||||||||||||||||||||||||||||||
| Oxidation states | +2, +3 (a mildly basic oxide) | |||||||||||||||||||||||||||||
| Electronegativity | Pauling scale: 1.13 (?) | |||||||||||||||||||||||||||||
| Ionization energies |
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| Atomic radius | empirical: 183 pm | |||||||||||||||||||||||||||||
| Covalent radius | 199 pm | |||||||||||||||||||||||||||||
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| Other properties | ||||||||||||||||||||||||||||||
| Natural occurrence | from decay | |||||||||||||||||||||||||||||
| Crystal structure | double hexagonal close-packed (dhcp) (hP4) | |||||||||||||||||||||||||||||
| Lattice constants |  c = 1.1739 pm (at 20 °C)[1] | |||||||||||||||||||||||||||||
| Thermal expansion | 9.0×10−6/K (at r.t.)[2][a] | |||||||||||||||||||||||||||||
| Thermal conductivity | 17.9 W/(m⋅K) | |||||||||||||||||||||||||||||
| Electrical resistivity | est. 0.75 µΩ⋅m (at r.t.) | |||||||||||||||||||||||||||||
| Magnetic ordering | paramagnetic[3] | |||||||||||||||||||||||||||||
| Young's modulus | α form: est. 46 GPa | |||||||||||||||||||||||||||||
| Shear modulus | α form: est. 18 GPa | |||||||||||||||||||||||||||||
| Bulk modulus | α form: est. 33 GPa | |||||||||||||||||||||||||||||
| Poisson ratio | α form: est. 0.28 | |||||||||||||||||||||||||||||
| CAS Number | 7440-12-2 | |||||||||||||||||||||||||||||
| History | ||||||||||||||||||||||||||||||
| Discovery | Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin (1945) | |||||||||||||||||||||||||||||
| Named by | Grace Mary Coryell (1945) | |||||||||||||||||||||||||||||
| Isotopes of promethium | ||||||||||||||||||||||||||||||
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Promethium (/[invalid input: 'icon']pr[invalid input: 'ɵ']ˈmiːθiəm/ pro-MEE-thee-əm) is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only exclusively radioactive element besides technetium that is followed by chemical elements with stable isotopes.
History
Prediction
The existence of promethium was first predicted by Bohuslav Brauner in 1902. During his research on the chemical properties of rare earth elements he found that the difference between neodymium and samarium is larger than between the other lanthanides. This prediction was supported in 1914 by Henry Moseley who, having discovered that atomic number was an experimentally measurable property of elements, found that no known element had atomic number 61. With the knowledge of a gap in the periodic table several groups started to search for the predicted element among other rare earths in the natural environment.
Florentium and Illinium
The first claim of a discovery was published by Italian scientists Luigi Rolla and Lorenzo Fernandes from Florence. After separating a didymium nitrate concentrate from the Brazilian mineral monazite by fractionated crystallisation, they yielded a solution containing mostly samarium. This solution gave x-ray spectra attributed to samarium and element 61. In honor of their city they named element 61 Florentium. The results were published in 1926, but the scientists claimed that the experiments were done in 1924.[5][6][7][8][9][10]
Also in 1926, a group of scientists from the University of Illinois at Urbana-Champaign, Smith Hopkins and Len Yntema published the discovery of element 61. They named it illinium, after the university.[11][12][13]
Both of these reported discoveries are now known to be erroneous because there are no stable or long-lived isotopes of promethium, hence there was none to be found in these sources.
True promethium
Promethium was first produced and characterized at Oak Ridge National Laboratory (ORNL) in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell by separation and analysis of the fission products of uranium fuel irradiated in the Graphite Reactor; however, being too busy with military-related research during World War II, they did not announce their discovery until 1947.[14] The name promethium is derived from Prometheus, the Titan, in Greek mythology, who stole fire from Mount Olympus and brought it down to mankind. The name was suggested by Grace Mary Coryell, Charles Coryell's wife, who felt that they were stealing fire from the gods.
In 1963, ion-exchange methods were used at ORNL to prepare about ten grams of promethium from nuclear reactor fuel processing wastes.[15][16]
Today, promethium is still recovered from the byproducts of uranium fission; it can also be produced by bombarding 146Nd with neutrons, turning it into 147Nd which decays into 147Pm through beta decay with a half-life of 11 days.
Occurrence
Promethium can be formed in nature as a product of spontaneous fission of uranium-238 and alpha decay of europium-151. Only trace amounts can be found in naturally occurring ores: a sample of pitchblende has been found to contain promethium at a concentration of four parts per quintillion (1018) by mass.[17] It was calculated that the equilibrium mass of promethium in the earth's crust is about 560g due to uranium fission and about 12g due to the recently observed alpha decay of europium-151.[18]
Promethium has also been identified in the spectrum of the star HR 465 in Andromeda, and possibly HD 101065 (Przybylski's star) and HD 965.[19]
Characteristics
Physical properties
Promethium's longest lived isotope 145Pm is a soft beta emitter with a half-life of 17.7 years. It does not emit gamma rays, but beta particles impinging on elements of high atomic numbers can generate x-rays, and a sample of 145Pm does produce some such soft x-ray radiation in addition to beta particles.
Pure promethium exists in two allotropic forms, and its chemistry is similar to other lanthanides. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity.
Chemical properties
Promethium metal tarnishes slowly in air and burns readily at 150 °C to form promethium(III) oxide:
- 4 Pm + 3 O2 → 2 Pm2O3
Promethium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form promethium hydroxide:
- 2 Pm (s) + 6 H2O (l) → 2 Pm(OH)3 (aq) + 3 H2 (g)
Promethium metal reacts with all the halogens:
- 2 Pm (s) + 3 F2 (g) → 2 PmF3 (s)
- 2 Pm (s) + 3 Cl2 (g) → 2 PmCl3 (s)
- 2 Pm (s) + 3 Br2 (g) → 2 PmBr3 (s)
- 2 Pm (s) + 3 I2 (g) → 2 PmI3 (s)
Promethium(III) iodide may also be synthesized by reacting PmX3 (X = Cl, Br) with hydrogen iodide at 400 °C:
- 2 PmX3(s) + 3HI(g) → PmI3(s) + 3HX(g)
Promethium dissolves readily in dilute sulfuric acid to form solutions containing the pink Pm(III) ions, which exist as a [Pm(OH2)9]3+ complexes:[20]
- 2 Pm(s) + 3 H2SO4 (aq) → 2 Pm3+ (aq) + 3 (SO4)2- (aq) + 3 H2 (g)
Promethium(III) ions form an insoluble, hygroscopic oxalate when dissolved in aqueous H2C2O4:
- 2 Pm3+(aq) + C2O42- (aq) → Pm2(C2O4)3•xH2O(s)
Isotopes
Thirty-six radioisotopes of promethium have been characterized, with the most stable being 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years. All of the remaining radioactive isotopes have half-lives that are less than 364 days, and the majority of these have half lives that are less than 27 seconds. This element also has 11 meta states with the most stable being 148Pmm (T½ 41.29 days), 152Pmm2 (T½ 13.8 minutes) and 152Pmm (T½ 7.52 minutes).
The isotopes of promethium range in atomic weight from 127.9482600 u (128Pm) to 162.9535200 u (163Pm). The primary decay mode before the longest-lived isotope, 145Pm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 145Pm are neodymium (Nd) isotopes and the primary products after are samarium (Sm) isotopes.
Along with technetium, promethium is one of only two elements with atomic number less than 83 that have only unstable isotopes, which is a rarely occurring effect of the liquid drop model and stabilities of neighbor element isotopes.
Applications
Uses for promethium include:
- As a beta radiation source for thickness gauges.
- As a light source for signals that require reliable, independent operation (using phosphor to absorb the beta radiation and produce light). In particular, Promethium(III) chloride (PmCl3) mixed with zinc sulfide (ZnS) was used for a time as a major luminous paint for watches after radium was discontinued. This mixture is still occasionally used for some luminous paint applications (though most such uses requiring radioactive materials have switched to tritium for safety reasons).
- In an atomic battery in which cells convert the beta emissions into electric current, yielding a useful life of about five years, using Pm-147.
- Promethium has possible future uses in portable X-ray sources, and as auxiliary heat or power sources for space probes and satellites (although the alpha emitter plutonium-238 has become standard for most space-exploration related uses – see Radioisotope thermoelectric generators).
Precautions
Promethium must be handled with great care because of its high radioactivity. In particular, promethium can emit X-rays during its beta decay. It is expected to have biological toxicity comparable with beta emitters of similar half life, for example iodine-131. It is not as hazardous as alpha emitters such as the transuranics, due to the far lower relative biological effectiveness of beta emitters over alpha emitters. Promethium has no biological role.
Compounds
Promethium compounds include:
- Chlorides
- PmCl3 (lavender)
- Bromides
- PmBr3 (coral - red)
- Fluorides
- PmF3 (purple - pink)
- Nitrates
- Oxalates
- Oxides
References
- ^ a b c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
- ^ Cverna, Fran (2002). "Ch. 2 Thermal Expansion". ASM Ready Reference: Thermal properties of metals (PDF). ASM International. ISBN 978-0-87170-768-0.
- ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
- ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- ^ Rolla, Luigi; Fernandes, Lorenzo (1926). "Über das Element der Atomnummer 61". Zeitschrift für anorganische und allgemeine Chemie. 157: 371. doi:10.1002/zaac.19261570129.
- ^ Noyes, W. A. (1927). "Florentium or Illinium?". Nature. 120: 14. doi:10.1038/120014c0.
- ^ Rolla, L.; Fernandes, L. (1927). "Florentium or Illinium?". Nature. 119: 637. doi:10.1038/119637a0.
- ^ Rolla, Luigi; Fernandes, Lorenzo (1928). "Florentium. II". Zeitschrift für anorganische und allgemeine Chemie. 169: 319. doi:10.1002/zaac.19281690128.
- ^ Rolla, Luigi; Fernandes, Lorenzo (1927). "Florentium". Zeitschrift für anorganische und allgemeine Chemie. 163: 40. doi:10.1002/zaac.19271630104.
- ^ Rolla, Luigi; Fernandes, Lorenzo (1927). "Über Das Element der Atomnummer 61 (Florentium)". Zeitschrift für anorganische und allgemeine Chemie. 160: 190. doi:10.1002/zaac.19271600119.
- ^ Harris, J. A.; Yntema, L. F.; Hopkins, B. S. (1926). "The Element of Atomic Number 61; Illinium". Nature. 117: 792. doi:10.1038/117792a0.
- ^ Brauner, BOHUSLAV (1926). "The New Element of Atomic Number 61: Illinium". Nature. 118: 84. doi:10.1038/118084b0.
- ^ Meyer, R. J.; Schumacher, G.; Kotowski, A. (1926). "Über das Element 61 (Illinium)". Naturwissenschaften. 14: 771. doi:10.1007/BF01490264.
- ^ "Discovery of Promethium". ORNL Review. 36 (1). 2003. Retrieved 2006-09-17.
- ^ Lee, Chung-Sin; Wang, Yun-Ming; Cheng, Wu-Long; Ting, Gann (1989). "Chemical study on the separation and purification of promethium-147". Journal of Radioanalytical and Nuclear Chemistry Articles. 130: 21. doi:10.1007/BF02037697.
- ^ "ION EXCHANGE PURIFICATION OF PROMETHIUM-147 AND ITS SEPARATION FROM AMERICIUM-241, WITH DIETHYLENETRIAMINEPENTA-ACETIC ACID AS THE ELUANT" (PDF).
- ^ Attrep, Moses, Jr. (1968). "Promethium in pitchblende". Journal of Inorganic and Nuclear Chemistry. 30 (3): 699–703. doi:10.1016/0022-1902(68)80427-0.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ P. Belli, R. Bernabei, F. Cappella, R. Cerulli, C.J. Dai, F.A. Danevich, A. d’Angelo, A. Incicchitti, V.V. Kobychev, S.S. Nagorny, S. Nisi, F. Nozzoli, D. Prosperi, V.I. Tretyak, S.S. Yurchenko (2007). "Search for α decay of natural Europium". Nuclear Physics A. 789: 15–29. doi:10.1016/j.nuclphysa.2007.03.001.
{{cite journal}}: Cite has empty unknown parameter:|month=(help)CS1 maint: multiple names: authors list (link) - ^ C. R. Cowley, W. P. Bidelman, S. Hubrig, G. Mathys, and D. J. Bord (2004). "On the possible presence of promethium in the spectra of HD 101065 (Przybylski's star) and HD 965". Astronomy & Astrophysics. 419: 1087–1093. Bibcode:2004A&A...419.1087C. doi:10.1051/0004-6361:20035726.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ "Chemical reactions of Promethium". Webelements. Retrieved 2009-06-06.
External links
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