Symbol: Np
Atomic Number: 93
Atomic Weight: 237.048
Element Classification: Radioactive Rare Earth Element (Actinide Series)
Discovered By: E.M. McMillan, P.H. Abelson
Discovery Date: 1940 (United States)
Name Origin: Named for the planet Neptune.
Density (g/cc): 20.25
Melting Point (K): 913
Boiling Point (K): 4175
Appearance: Silvery metal
Atomic Radius (pm): 130
Atomic Volume (cc/mol): 21.1
Covalent Radius (pm): n/a
Ionic Radius: 95 (+4e) 110 (+3e)
Specific Heat (@20°C J/g mol): n/a
Fusion Heat (kJ/mol): (9.6)
Evaporation Heat (kJ/mol): 336
Thermal Conductivity (@25°C W/m K):
Debye Temperature (K): n/a
Pauling Negativity Number: 1.36
First Ionizing Energy (kJ/mol): n/a
Oxidation States: 6, 5, 4, 3
Electronic Configuration: [Rn] 5f⁴ 6d¹ 7s²
Lattice Structure: Orthorhombic (ORC)
Lattice Constant (Å): 4.720
Lattice C/A Ratio: n/a