Protactinium

ElementProtactiniumSymbolPa
Atomic Number91Molar Mass231.04 g mol-1
Electron Configuration[Rn]5f26d17s2Normal Statesolid metal
Density @STP15.37 g cm-3Melting Point1572oC
Boiling Point4000oCStable Isotopesnone
Atomic Radius161 pmIonic Radius89 (5+) pm
Electronegativity (Pauling)1.5Ionization Energy (1st)568 kJ mol-1
Ionization Energy (2nd)1129 kJ mol-1Ionization Energy (3rd)1814 kJ mol-1
Molar Heat Capacity22.9 J K-1mol-1Standard Molar Entropy198.1 J K-1mol-1
Enthalpy of Fusion16.7 kJ mol-1Enthalpy of Vapourization481 kJ mol-1
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