Symbol Np Atomic radius: pm - Fusion: kJ/Mole 3.20
Name Neptunium Ionic radius: pm (+5)75 Boiling point: C -
Atomic number 93 Electron affinity - Melting point: C 644
Atomic weight 237.0 1st  ion potential 6.27 Specific Heat Cap: J/(g K) -
Classification Trans metal Natural form Solid Thermal Cond: W/(cm K) 0.06
Configuration [Rn]5f46d17s2 Crystal structure Ortho Electrical Cond 0.00822
Oxidation states 3,4,5,6 Density 20.2 Abundance: mg/kg-crust Synthetic
Electronegativity 1.3 Vaporization: kJ/Mole 337.0    
Edwin M.McMillan and Philip H. Abelson first found neptunium in 1940 after uranium had been bombarded by neutrons. Uses - a component in neutron detection instruments