Protactinium (Pa) — Atomic Data, Electron Shells & Reactions

Atomic Number (Z) 91 IUPAC Symbol Pa Standard Atomic Weight 231.04 g/mol Period / Group / Block 7 / f-block / f-block Condensed Electron Config [Rn] 5f2 6d1 7s2 Full Subshell Config 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f2 6s2 6p6 6d1 7s2 Principal Shell Occupancy [2, 8, 18, 32, 20, 9, 2] Pauling Electronegativity 1.5 First Ionization Energy 568 kJ/mol Covalent Radius 200 pm Melting Point 1841 K (1567.85 °C) Boiling Point 4300 K (4026.85 °C) Density 15.37 g/cm³ Oxidation States +5, +4