91Pa231.035
Protactinium
ActinidesBlock fPeriod 7solid at 20 °C
- Configuration :
- [Rn] 5f² 6d¹ 7s²
- Atomic mass :
- 231.03588 u
3D Bohr-model representation of the Protactinium atom (symbol Pa, atomic number Z=91). Electron shell configuration: 2, 8, 18, 32, 20, 9, 2 electrons.
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Bohr model · educational
Bohr model of protactinium
Protactinium (Pa) has 91 electrons, spread over 7 shells. The diagram places them on circles around the nucleus, from the K shell — the closest — outward.
| Shell | Electrons |
|---|---|
| K (n = 1) | 2 |
| L (n = 2) | 8 |
| M (n = 3) | 18 |
| N (n = 4) | 32 |
| O (n = 5) | 20 |
| P (n = 6) | 9 |
| Q (n = 7) | 2 |
The Bohr model is a teaching picture: electrons do not travel in circular orbits, but the number of electrons per shell is exact.
Electron configuration
Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f² 6d¹ 7s²
Short[Rn] 5f² 6d¹ 7s²
Valence electrons5
KLMNOPQ shells
K2
L8
M18
N32
O20
P9
Q2
Electronegativity
Pauling1.5
Allen—
Mulliken (eV)—
Atomic radii
Empirical180 pm
Calculated—
Covalent200 pm
Van der Waals—
Ionic radii (Shannon-Prewitt)
+578 pm
Successive ionisation energies
I₁568 kJ/mol
Electron affinity—
Oxidation states
+2+3+4+5
Bold states = most common.
Warm-up
Protactinium — do you remember?
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