Characteristics
Silvery in appearance, neptunium metal is chemically fairly reactive and is found in at least three allotropes:
- α-neptunium, orthorhombic, density 20.45 g/cm3
- β-neptunium (above 280 °C), tetragonal, density (313 °C) 19.36 g/cm3
- γ-neptunium (above 577 °C), cubic, density (600 °C) 18 g/cm3
Neptunium has the largest liquid range of any element, 3363 K, between the melting point and boiling point. It is the densest of all the actinides.
Read more about this topic: Neptunium