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91Pa231.036
Protactinium
ActinideProtactinium is a chemical element with symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume +4 and even +2 or +3 states.
Phase: SolidAppearance: bright, silvery metallic luster
2, 8, 18, 32, 20, 9, 2
Physical Properties
Atomic Mass231.035882 u
Density15.37 g/cm³
Melting Point1841 K
Boiling Point4300 K
Period7
PhaseSolid
Chemical Properties
Electron Configuration1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f2 6d1
Semantic Config[Rn] 5f2 6d1 7s2
Shells2, 8, 18, 32, 20, 9, 2
Electron Affinity53.03 kJ/mol
Electronegativity1.5
Ionization Energies
IE1: 568 kJ/mol
Discovery