| From Wikipedia, the free encyclopediaProtactinium 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. | |||||||||
Protactinium in the periodic table | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | Pa | ||||||||
| Atomic number | 91 | ||||||||
| Group | 0 | ||||||||
| Period | 7 | ||||||||
| Block | f | ||||||||
| Element category | Actinide | ||||||||
Physical properties | |||||||||
| Phase at STP | Solid | ||||||||
| Density | 15.37 g/cm3 | ||||||||
| Atomic weight | 231.036 u | ||||||||
| Melting point | 1841 K 1567.85 °C 2854.13 °F | ||||||||
| Boiling point | 4300 K 4026.85 °C 7280.33 °F | ||||||||
Atomic properties | |||||||||
| Electronegativity (Pauling Scale) | 1.5 | ||||||||
| Electron affinity | 53.03 kJ/mol | ||||||||
| Oxidation states | +2, +3, +4, +5 (a weakly basic oxide) | ||||||||
| Ionization energies |
| ||||||||
Electron configuration | |||||||||
| Elektronkonfiguration (shorthand) | [Rn] 5f2 6d1 7s2 | ||||||||
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f2 6s2 6p6 6d1 7s2 | ||||||||
| Electrons per shell | 2, 8, 18, 32, 20, 9, 2 | ||||||||
History | |||||||||
| Discovered | 1913 | ||||||||
| Discovered by | Oswald Helmuth Göhring Kazimierz Fajans | ||||||||
| Named by | Otto Hahn | ||||||||