Neptunium(V) oxide
| Names | |
|---|---|
| IUPAC name
Neptunium(V) oxide
| |
| Other names
Neptunium pentoxide
Dineptunium pentoxide | |
| Identifiers | |
3D model (JSmol)
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|
| |
| |
| Properties | |
| Np2O5 | |
| Molar mass | 554.09 g/mol[1] |
| Appearance | Green crystals[2] |
| Density | 8.18 g/cm3[2] |
| Melting point | 427 °C; 800 °F; 700 K[3] (decomposes) |
| Insoluble[2] | |
| Related compounds | |
Other anions
|
Neptunium(V) fluoride |
Other cations
|
Protactinium(V) oxide Uranium(V) oxide |
| Neptunium(IV) oxide | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Neptunium(V) oxide or neptunium pentoxide is one of two stable oxides of neptunium, the other being neptunium(IV) oxide.[3] It has a chemical formula of Np2O5.[1]
History
[edit ]Neptunium(V) oxide was first synthesized in 1963 by passing ozone through molten lithium perchlorate containing neptunyl(V) ions and precipitating the product.[4]
Formation
[edit ]Neptunium(V) oxide can be formed from the calcination of other compounds of neptunium, such as neptunium(VI) oxide (NpO3·xH2O), neptunyl(V) hydroxide (NpO2OH), neptunyl(VI) hydroxide (NpO2(OH)2), or neptunium(V) nitrates (NpO(NO3)3 or NpO2NO3).[5] [6]
It can also be formed from the precipitation of neptunyl ions in solution:[2] [6]
- 2NpO+2(aq) + H2O(l) → Np2O5(cr) + H+(aq)
Reactions
[edit ]Neptunium(V) oxide decomposes at 700 K, forming neptunium(IV) oxide and oxygen gas:[3] [5]
- Np2O5 → 2 NpO2 + 1/2 O2
Np2O5 produced from the calcination of neptunyl(VI) hydroxide goes through an intermediate phase Np4O9 before reaching NpO2.[5]
Structure
[edit ]
Neptunium(V) oxide adopts a layered structure. Corresponding neptunium atoms in different layers are bridged by oxygen atoms, forming chains of neptunyl cations. Within each layer, neptunyl cations are linked by oxygen atoms.[2]
The crystal structure of neptunium(V) oxide contains three distinct neptunium sites. Two sites have a coordination geometry of pentagonal bipyramidal, and the other has a coordination geometry of tetragonal bipyramidal.[2]
Neptunium(V) oxide crystals are monoclinic, with space group P2/c, four formula units per unit cell, and unit cell dimensions a=8.17Å, b=6.58Å, c=9.313Å, and β=116.09°. They have a density of 8.18 g/cm3.[2]
Other properties
[edit ]Neptunium(V) oxide undergoes antiferromagnetic ordering at 22 K.[2]
References
[edit ]- ^ a b WebElements, https://www.webelements.com
- ^ a b c d e f g h Forbes, Tori Z.; Burns, Peter C.; Skanthakumar, S.; Soderholm, L. (14 Feb 2007). "Synthesis, Structure, and Magnetism of Np2O5". Journal of the American Chemical Society. 129 (10): 2760–2761. Bibcode:2007JAChS.129.2760F. doi:10.1021/ja069250r. PMID 17298069.
- ^ a b c Zhang, Lei; Dzik, Ewa A.; Sigmon, Ginger E.; Szymanowski, Jennifer E.S.; Navrotsky, Alexandra; Burns, Peter C. (2018). "Experimental thermochemistry of neptunium oxides: Np2O5 and NpO2". Journal of Nuclear Materials. 501: 398–403. doi:10.1016/j.jnucmat.2017年10月03日4.
- ^ Yoshida, Zenko; Johnson, Stephen; Kimura, Takaumi; Krsul, John (2011). "Neptunium". The Chemistry of the Actinide and Transactinide Elements. p. 724. doi:10.1007/978-94-007-0211-0_6. ISBN 978-1-4020-3555-5.
- ^ a b c Fahey, J. A.; Turcotte, R. P.; Chikalla, T. D. (1976). "Decomposition, stoichiometry and structure of neptunium oxides". Journal of Inorganic and Nuclear Chemistry. 38 (3): 495–500. doi:10.1016/0022-1902(76)80291-6.
- ^ a b Lemire, R. J. et al., Chemical Thermodynamics of Neptunium and Plutonium, Elsevier, Amsterdam, 2001.