56Ba137.327
Barium
Alkaline earth metalsBlock sPeriod 6Group 2solid at 20 °C
- Configuration :
- [Xe] 6s²
- Atomic mass :
- 137.327 u
- French :
- Baryum
3D Bohr-model representation of the Barium atom (symbol Ba, atomic number Z=56). Electron shell configuration: 2, 8, 18, 18, 8, 2 electrons.
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Bohr model · educational
Bohr model of barium
Barium (Ba) has 56 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) | 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
Precipitation reactions
Solubility product Ksp, precipitation conditions, precipitation titrations.
10 minElectron configuration
Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²
Short[Xe] 6s²
Valence electrons2
KLMNOPQ shells
K2
L8
M18
N18
O8
P2
Electronegativity
Pauling0.89
Allen0.881
Mulliken (eV)—
Atomic radii
Empirical215 pm
Calculated253 pm
Covalent215 pm
Van der Waals268 pm
Ionic radii (Shannon-Prewitt)
+2135 pm
Successive ionisation energies
I₁502.9 kJ/mol
I₂965.2 kJ/mol
I₃3600 kJ/mol
Electron affinity13.95 kJ/mol
Oxidation states
+1+2
Bold states = most common.
Warm-up
Barium — do you remember?
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