Neptunium(V) oxide or neptunium pentoxide is one of two stable

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

s of

neptunium Neptunium is a chemical element; it has chemical symbol, symbol Np and atomic number 93. A radioactivity, radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar Syste ...

, the other being neptunium(IV) oxide. It has a chemical formula of Np₂O₅.

History

Neptunium(V) oxide was first synthesized in 1963 by passing

ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

through molten

lithium perchlorate Lithium perchlorate is the inorganic compound with the formula LiClO4. This white or colourless crystalline salt is noteworthy for its high solubility in many solvents. It exists both in anhydrous form and as a trihydrate. Applications Inorgani ...

containing neptunyl(V) ions and precipitating the product.

Formation

Neptunium(V) oxide can be formed from the

calcination Calcination is thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), generally f ...

of other compounds of neptunium, such as neptunium(VI) oxide (NpO₃·''x''H₂O), neptunyl(V) hydroxide (NpO₂OH), neptunyl(VI) hydroxide (NpO₂(OH)₂), or

neptunium(V) nitrate Neptunium is a chemical element; it has symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar System, which uranium is named after. ...

s (NpO(NO₃)₃ or NpO₂NO₃).Lemire, R. J. et al., ''Chemical Thermodynamics of Neptunium and Plutonium'', Elsevier, Amsterdam, 2001. It can also be formed from the precipitation of neptunyl ions in solution: :

Reactions

Neptunium(V) oxide decomposes at 700 K, forming neptunium(IV) oxide and

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

gas: : Np₂O₅ produced from the calcination of neptunyl(VI) hydroxide goes through an intermediate phase Np₄O₉ before reaching NpO₂.

Structure

Neptunium(V) oxide adopts a layered structure. Corresponding neptunium atoms in different layers are

bridged Bridging may refer to: Construction * Building of bridges across a gap * Cross bracing used between joists to stabilize them Electronics and computing * In electronics, using a low source impedance to drive a large load impedance for maximum vol ...

by oxygen atoms, forming chains of neptunyl cations. Within each layer, neptunyl cations are linked by oxygen atoms. The crystal structure of neptunium(V) oxide contains three distinct neptunium sites. Two sites have a

coordination geometry The coordination geometry of an atom is the geometrical pattern defined by the atoms around the central atom. The term is commonly applied in the field of inorganic chemistry, where diverse structures are observed. The coordination geometry depen ...

of pentagonal bipyramidal, and the other has a coordination geometry of

tetragonal bipyramidal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square ...

. Neptunium(V) oxide crystals are

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

, with

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

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.

Other properties

Neptunium(V) oxide undergoes

antiferromagnetic In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring Spin (physics), spins (on different sublattices) pointing in oppos ...

ordering at 22 K.

References

{{Oxides Neptunium compounds Oxides