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| Names | |
|---|---|
| IUPAC name Neptunium(V) oxide | |
| Other names Neptunium pentoxide Dineptunium pentoxide | |
| Identifiers | |
3D model (JSmol) | |
| |
| |
| 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 | |
Otheranions | Neptunium(V) fluoride |
Othercations | Protactinium(V) oxide Uranium(V) oxide |
| Neptunium(IV) oxide | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Neptunium(V) oxide orneptunium pentoxide is one of two stableoxides ofneptunium, the other beingneptunium(IV) oxide.[3] It has a chemical formula of Np2O5.[1]
Neptunium(V) oxide was first synthesized in 1963 by passingozone through moltenlithium perchlorate containingneptunyl(V) ions and precipitating the product.[4]
Neptunium(V) oxide can be formed from thecalcination of other compounds of neptunium, such asneptunium(VI) oxide (NpO3·xH2O),neptunyl(V) hydroxide (NpO2OH),neptunyl(VI) hydroxide (NpO2(OH)2), orneptunium(V) nitrates (NpO(NO3)3 or NpO2NO3).[5][6]
It can also be formed from the precipitation of neptunyl ions in solution:[2][6]
Neptunium(V) oxide decomposes at 700 K, forming neptunium(IV) oxide andoxygen gas:[3][5]
Np2O5 produced from the calcination of neptunyl(VI) hydroxide goes through an intermediate phase Np4O9 before reaching NpO2.[5]
Neptunium(V) oxide adopts a layered structure. Corresponding neptunium atoms in different layers arebridged 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 acoordination geometry ofpentagonal bipyramidal, and the other has a coordination geometry oftetragonal bipyramidal.[2]
Neptunium(V) oxide crystals aremonoclinic, withspace group P2/c, four formula units per unit cell, and unit cell dimensionsa=8.17Å,b=6.58Å,c=9.313Å, andβ=116.09°. They have a density of 8.18 g/cm3.[2]
Neptunium(V) oxide undergoesantiferromagnetic ordering at 22 K.[2]