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Promethium compounds

From Wikipedia, the free encyclopedia
Promethium(III) nitrate, a promethium compound[1]

Promethium compounds are compounds containing the elementpromethium, which normally take the +3oxidation state. Promethium belongs to thecerium group of lanthanides and is chemically very similar to the neighboring elements.[2] Because of its instability, chemical studies of promethium are incomplete. Even though a few compounds have been synthesized, they are not fully studied; in general, they tend to be pink or red in color.[3][4] Treatment of acidic solutions containing Pm3+ ions withammonia results in a gelatinous light-brown sediment of hydroxide, Pm(OH)3, which is insoluble in water.[5] When dissolved inhydrochloric acid, a water-soluble yellow salt, PmCl3, is produced;[5] similarly, when dissolved in nitric acid, a nitrate results, Pm(NO3)3. The latter is also well-soluble; when dried, it forms pink crystals, similar to Nd(NO3)3.[5] The electron configuration for Pm3+ is [Xe] 4f4, and the color of the ion is pink. The ground state term symbol is5I4.[6] The sulfate is slightly soluble, like the other cerium group sulfates. Cell parameters have been calculated for its octahydrate; they lead to conclusion that the density of Pm2(SO4)3·8 H2O is 2.86 g/cm3.[7] The oxalate, Pm2(C2O4)3·10 H2O, has the lowest solubility of all lanthanide oxalates.[8]

Unlike the nitrate, theoxide is similar to the corresponding samarium salt and not the neodymium salt. As-synthesized, e.g. by heating the oxalate, it is a white or lavender-colored powder with disordered structure.[5] This powder crystallizes in a cubic lattice upon heating to 600 °C. Further annealing at 800 °C and then at 1750 °C irreversibly transforms it tomonoclinic andhexagonal phases, respectively, and the last two phases can be interconverted by adjusting the annealing time and temperature.[9]

Formulasymmetryspace groupNoPearson symbola (pm)b (pm)c (pm)Zdensity,
g/cm3
α-Pmdhcp[10][11]P63/mmc194hP4365365116547.26
β-Pmbcc[11]Fm3m225cF441041041046.99
Pm2O3cubic[9]Ia3206cI80109910991099166.77
Pm2O3monoclinic[9]C2/m12mS30142236589167.40
Pm2O3hexagonal[9]P3m1164hP5380.2380.2595.417.53

Promethium forms only one stable oxidation state, +3, in the form of ions; this is in line with other lanthanides. According to its position in theperiodic table, the element cannot be expected to form stable +4 or +2 oxidation states; treating chemical compounds containing Pm3+ ions with strong oxidizing or reducing agents showed that the ion is not easily oxidized or reduced.[2]

Promethium halides[12]
Formulacolorcoordination
number		symmetryspace groupNoPearson symbolm.p. (°C)
PmF3Purple-pink11hexagonalP3c1165hP241338
PmCl3Lavender9hexagonalP63/mc176hP8655
PmBr3Red8orthorhombicCmcm63oS16624
α-PmI3Red8orthorhombicCmcm63oS16α→β
β-PmI3Red6rhombohedralR3148hR24695

Bibliography

[edit]
  • Lavruk︠h︡ina, Avgusta Konstantinovna; Pozdni︠a︡kov, Aleksandr Aleksandrovich (1970).Analytical chemistry of technetium, promethium, astatine and francium.S2CID 94160197.

References

[edit]
  1. ^Driscoll, Darren M.; White, Frankie D.; Pramanik, Subhamay; Einkauf, Jeffrey D.; Ravel, Bruce; Bykov, Dmytro; Roy, Santanu; Mayes, Richard T.; Delmau, Lætitia H.; Cary, Samantha K.; Dyke, Thomas; Miller, April; Silveira, Matt; VanCleve, Shelley M.; Davern, Sandra M. (May 2024)."Observation of a promethium complex in solution".Nature.629 (8013):819–823.Bibcode:2024Natur.629..819D.doi:10.1038/s41586-024-07267-6.ISSN 1476-4687.PMC 11111410.PMID 38778232.
  2. ^abLavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 120.
  3. ^Emsley, J. (2011).Nature's Building Blocks: An A-Z Guide to the Elements. OUP Oxford. p. 429.ISBN 978-0-19-257046-8.
  4. ^promethium. Encyclopædia Britannica Online
  5. ^abcdLavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 121.
  6. ^Aspinall, H. C. (2001).Chemistry of the f-block elements. Gordon & Breach. p. 34, Table 2.1.ISBN 978-9056993337.
  7. ^Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 122.
  8. ^Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 123.
  9. ^abcdChikalla, T. D.; McNeilly, C. E.; Roberts, F. P. (1972). "Polymorphic Modifications of Pm2O3".Journal of the American Ceramic Society.55 (8): 428.doi:10.1111/j.1151-2916.1972.tb11329.x.
  10. ^Pallmer, P. G.; Chikalla, T. D. (1971). "The crystal structure of promethium".Journal of the Less Common Metals.24 (3): 233.doi:10.1016/0022-5088(71)90101-9.
  11. ^abGschneidner Jr., K.A. (2005)."Physical Properties of the rare earth metals"(PDF). In Lide, D. R. (ed.).CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, FL: CRC Press.ISBN 978-0-8493-0486-6. Archived fromthe original(PDF) on 2012-09-18. Retrieved2012-06-20.
  12. ^Cotton, Simon (2006).Lanthanide And Actinide Chemistry. John Wiley & Sons. p. 117.ISBN 978-0-470-01006-8.
Chemical compounds by element
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