Promethium compounds - Wiki slovník

Promethium compounds are compounds containing the element promethium, which normally take the +3 oxidation state. Promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements.^[1] 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.^[2]^[3] Treatment of acidic solutions containing Pm³⁺ ions with ammonia results in a gelatinous light-brown sediment of hydroxide, Pm(OH)₃, which is insoluble in water.^[4] When dissolved in hydrochloric acid, a water-soluble yellow salt, PmCl₃, is produced;^[4] 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.^[4] The electron configuration for Pm³⁺ is 4f⁴, and the color of the ion is pink. The ground state term symbol is ⁵I₄.^[5] 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.^[6] The oxalate, Pm₂(C₂O₄)₃·10 H₂O, has the lowest solubility of all lanthanide oxalates.^[7]

Unlike the nitrate, the oxide 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.^[4] 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 to monoclinic and hexagonal phases, respectively, and the last two phases can be interconverted by adjusting the annealing time and temperature.^[8]

Formula	symmetry	space group	No	Pearson symbol	a (pm)	b (pm)	c (pm)	Z	density, g/cm³
α-Pm	dhcp^[9]^[10]	P6₃/mmc	194	hP4	365	365	1165	4	7.26
β-Pm	bcc^[10]	Fm3m	225	cF4	410	410	410	4	6.99
Pm₂O₃	cubic^[8]	Ia3	206	cI80	1099	1099	1099	16	6.77
Pm₂O₃	monoclinic^[8]	C2/m	12	mS30	1422	365	891	6	7.40
Pm₂O₃	hexagonal^[8]	P3m1	164	hP5	380.2	380.2	595.4	1	7.53

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 the periodic 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.^[1]

Promethium halides^[11]
Formula	color	coordination number	symmetry	space group	No	Pearson symbol	m.p. (°C)
PmF₃	Purple-pink	11	hexagonal	P3c1	165	hP24	1338
PmCl₃	Lavender	9	hexagonal	P6₃/mc	176	hP8	655
PmBr₃	Red	8	orthorhombic	Cmcm	63	oS16	624
α-PmI₃	Red	8	orthorhombic	Cmcm	63	oS16	α→β
β-PmI₃	Red	6	rhombohedral	R3	148	hR24	695

Bibliography

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

References

^ ^a ^b Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 120.
^ Emsley, J. (2011). Nature's Building Blocks: An A-Z Guide to the Elements. OUP Oxford. p. 429. ISBN 978-0-19-257046-8.
^ promethium. Encyclopædia Britannica Online
^ ^a ^b ^c ^d Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 121.
^ Aspinall, H. C. (2001). Chemistry of the f-block elements. Gordon & Breach. p. 34, Table 2.1. ISBN 978-9056993337.
^ Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 122.
^ Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 123.
^ ^a ^b ^c ^d Chikalla, 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.
^ 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.
^ ^a ^b Gschneidner 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 from the original (PDF) on 2012-09-18. Retrieved 2012-06-20.
^ Cotton, Simon (2006). Lanthanide And Actinide Chemistry. John Wiley & Sons. p. 117. ISBN 978-0-470-01006-8.

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[FOOTNOTELavruk︠h︡inaPozdni︠a︡kov1970120-1] Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 120.

[2] Emsley, J. (2011). Nature's Building Blocks: An A-Z Guide to the Elements. OUP Oxford. p. 429. ISBN 978-0-19-257046-8.

[brit-3] romethium. Encyclopædia Britannica Online

[FOOTNOTELavruk︠h︡inaPozdni︠a︡kov1970121-4] Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 121.

[5] Aspinall, H. C. (2001). Chemistry of the f-block elements. Gordon & Breach. p. 34, Table 2.1. ISBN 978-9056993337.

[FOOTNOTELavruk︠h︡inaPozdni︠a︡kov1970122-6] Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 122.

[FOOTNOTELavruk︠h︡inaPozdni︠a︡kov1970123-7] Lavruk︠h︡ina & Pozdni︠a︡kov 1970, p. 123.

[PmO-8] Chikalla, 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.

[str-9] 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.

[CRCrare-10] Gschneidner 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 from the original (PDF) on 2012-09-18. Retrieved 2012-06-20.

[11] Cotton, Simon (2006). Lanthanide And Actinide Chemistry. John Wiley & Sons. p. 117. ISBN 978-0-470-01006-8.

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