91
Pa
231.036
Protactinium
Actinide
Period 7
Block f
Protactinium is a chemical element of the periodic table with chemical symbol Pa and atomic number 91 with an atomic weight of 231.036 u and is classed as actinide. Protactinium is solid at room temperature.
Protactinium in the periodic table
| Symbol | Pa |
| Atomic number | 91 |
| Group | - |
| Period | 7 |
| Block | f |
| Classification | Actinide |
| Appearance | Bright, silvery metallic luster |
| Color | Silver |
| Number of protons | 91 p+ |
| Number of neutrons | 140 n0 |
| Number of electrons | 91 e- |
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.
Physical properties
| Phase at STP | Solid |
| Density | 15.37 g/cm3 |
| Atomic weight | 231.036 u |
Thermal properties
| Melting point | 1841 K 1567.85 °C 2854.13 °F |
| Boiling point | 4300 K 4026.85 °C 7280.33 °F |
| Heat of vaporization | 481.2 kJ/mol |
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 |
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Electron configuration for protactinium
Electron configuration Shorthand configuration | [Rn] 5f2 6d1 7s2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Full configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f2 6s2 6p6 6d1 7s2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Electron configuration chart |
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| Electrons per shell | 2, 8, 18, 32, 20, 9, 2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Outer shell electrons | 2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Valency electrons | 2,3,4,5 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Bohr model | Figure: Shell diagram of Protactinium (Pa) atom. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Orbital Diagram
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The history of Protactinium
| Prediction | Dmitri Mendeleev |
| Discovery | Oswald Helmuth Göhring, Kazimierz Fajans (1913) |
| Named by | Otto Hahn, Lise Meitner (1917) |
Discovery of protactinium Protactinium was first identified in 1913 by Kazimierz Fajans and Oswald Göhring as a short-lived isotope and named brevium. A longer-lived isotope, Pa-231, was isolated by Lise Meitner and Otto Hahn in 1917-1918, who proposed the present name meaning "parent of actinium" because it decays to actinium. It is one of the rarest naturally occurring elements. | |
| Original word | protos + aktinos |
| Language of origin | Greek |
| Name source | Properties |
| Meaning | “First ray” |
Naming The name is derived from the Greek 'protos' (first) and aktinos (ray): protactinium decays into actinium and is therefore the 'parent of actinium'. | |