← Periodic Table
93Np237.000
Neptunium
ActinideNeptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.
Phase: SolidAppearance: silvery metallic
2, 8, 18, 32, 22, 9, 2
Physical Properties
Atomic Mass237 u
Density20.45 g/cm³
Melting Point912 K
Boiling Point4447 K
Molar Heat29.46 J/(mol·K)
Period7
PhaseSolid
Chemical Properties
Electron Configuration1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f4 6d1
Semantic Config[Rn] 5f4 6d1 7s2
Shells2, 8, 18, 32, 22, 9, 2
Electron Affinity45.85 kJ/mol
Electronegativity1.36
Ionization Energies
IE1: 604.5 kJ/mol
Discovery
Discovered byEdwin McMillan