The Periodic Table of Elements
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91
Pa
Protactinium
Summary
Protactinium 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.
Block: f
Period: 7
Group: 3
Atomic Mass: 231.036 g/mol (amu)
Discovered By: William Crookes
Phase: Solid
Boiling Point: 4300 K
Melting Point: 1841 K
Type: actinide
Density: 15.37 g/cm3
Electron Configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f2 6d1
Electron Configuration (Semantic): [Rn] 5f2 6d1 7s2