Neptunium(VII) oxide-hydroxide
Neptunium oxide-hydroxide is a chemical compound which has neptunium in its highest oxidation state of +7. This compound reacts with basic salts such as potassium hydroxide to form neptunates and water.
Neptunium oxide-hydroxide is stable in an alkaline solution, however, it is slowly reduced to Np in an acidic solution. In water, it forms a greenish solution. This compound decomposes slowly to an oxidized solid.