Neptunium (Np) — Atomic Data, Electron Shells & Reactions

Atomic Number (Z) 93 IUPAC Symbol Np Standard Atomic Weight 237 g/mol Period / Group / Block 7 / f-block / f-block Condensed Electron Config [Rn] 5f4 6d1 7s2 Full Subshell Config 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f4 6s2 6p6 6d1 7s2 Principal Shell Occupancy [2, 8, 18, 32, 22, 9, 2] Pauling Electronegativity 1.36 First Ionization Energy 605 kJ/mol Covalent Radius 190 pm Melting Point 917 K (643.85 °C) Boiling Point 4273 K (3999.85 °C) Density 20.45 g/cm³ Oxidation States +5, +4, +3