57La138.905
Lanthanum
LanthanidesBlock fPeriod 6solid at 20 °C
- Configuration :
- [Xe] 5d¹ 6s²
- Atomic mass :
- 138.90547 u
- French :
- Lanthane
3D Bohr-model representation of the Lanthanum atom (symbol La, atomic number Z=57). Electron shell configuration: 2, 8, 18, 18, 9, 2 electrons.
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Bohr model · educational
Bohr model of lanthanum
Lanthanum (La) has 57 electrons, spread over 6 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) | 18 |
| O (n = 5) | 9 |
| P (n = 6) | 2 |
The Bohr model is a teaching picture: electrons do not travel in circular orbits, but the number of electrons per shell is exact.
Related lesson
s, p, d and f orbitals
3D geometry of orbitals, spherical harmonics, lobes and nodes. Chemical consequences.
14 minElectron configuration
Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²
Short[Xe] 5d¹ 6s²
Valence electrons3
KLMNOPQ shells
K2
L8
M18
N18
O9
P2
Electronegativity
Pauling1.1
Allen—
Mulliken (eV)—
Atomic radii
Empirical195 pm
Calculated226 pm
Covalent207 pm
Van der Waals—
Ionic radii (Shannon-Prewitt)
+3103.2 pm
Successive ionisation energies
I₁538.1 kJ/mol
I₂1067 kJ/mol
I₃1850.3 kJ/mol
Electron affinity—
Oxidation states
+2+3
Bold states = most common.
Warm-up
Lanthanum — do you remember?
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