3D Bohr-model representation of the Caesium atom (symbol Cs, atomic number Z=55). Electron shell configuration: 2, 8, 18, 18, 8, 1 electrons.
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Bohr model · educational
Bohr model of caesium
Caesium (Cs) has 55 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) | 8 |
| P (n = 6) | 1 |
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
Atomic spectra
Emission, absorption, Balmer/Lyman series. Links to energy levels and allowed transitions.
13 minElectron configuration
Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹
Short[Xe] 6s¹
Valence electrons1
KLMNOPQ shells
K2
L8
M18
N18
O8
P1
Electronegativity
Pauling0.79
Allen0.659
Mulliken (eV)—
Atomic radii
Empirical260 pm
Calculated298 pm
Covalent244 pm
Van der Waals343 pm
Ionic radii (Shannon-Prewitt)
+1167 pm
Successive ionisation energies
I₁375.7 kJ/mol
I₂2234.3 kJ/mol
I₃3400 kJ/mol
Electron affinity45.5 kJ/mol
Oxidation states
-1+1
Bold states = most common.
Warm-up
Caesium — do you remember?
3 questions on this page. The right answer shows every time, and nothing is asked of you to play.
No account · one minute