38Sr87.62
Strontium
Alkaline earth metalsBlock sPeriod 5Group 2solid at 20 °C
- Configuration :
- [Kr] 5s²
- Atomic mass :
- 87.62 u
3D Bohr-model representation of the Strontium atom (symbol Sr, atomic number Z=38). Electron shell configuration: 2, 8, 18, 8, 2 electrons.
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Bohr model · educational
Bohr model of strontium
Strontium (Sr) has 38 electrons, spread over 5 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) | 8 |
| O (n = 5) | 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 5s²
Short[Kr] 5s²
Valence electrons2
KLMNOPQ shells
K2
L8
M18
N8
O2
Electronegativity
Pauling0.95
Allen0.963
Mulliken (eV)—
Atomic radii
Empirical200 pm
Calculated219 pm
Covalent195 pm
Van der Waals249 pm
Ionic radii (Shannon-Prewitt)
+2118 pm
Successive ionisation energies
I₁549.5 kJ/mol
I₂1064.2 kJ/mol
I₃4138 kJ/mol
I₄5500 kJ/mol
I₅6910 kJ/mol
Electron affinity5.03 kJ/mol
Oxidation states
+1+2
Bold states = most common.
Warm-up
Strontium — do you remember?
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