69Tm168.934
Thulium
LanthanidesBlock fPeriod 6solid at 20 °C
- Configuration :
- [Xe] 4f¹³ 6s²
- Atomic mass :
- 168.934218 u
3D Bohr-model representation of the Thulium atom (symbol Tm, atomic number Z=69). Electron shell configuration: 2, 8, 18, 31, 8, 2 electrons.
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Bohr model · educational
Bohr model of thulium
Thulium (Tm) has 69 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) | 31 |
| 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.
Electron configuration
Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹³ 6s²
Short[Xe] 4f¹³ 6s²
Valence electrons3
KLMNOPQ shells
K2
L8
M18
N31
O8
P2
Electronegativity
Pauling1.25
Allen—
Mulliken (eV)—
Atomic radii
Empirical175 pm
Calculated222 pm
Covalent190 pm
Van der Waals—
Ionic radii (Shannon-Prewitt)
+388 pm
Successive ionisation energies
I₁596.7 kJ/mol
I₂1160 kJ/mol
I₃2285 kJ/mol
I₄4120 kJ/mol
Electron affinity—
Oxidation states
+2+3
Bold states = most common.
Warm-up
Thulium — do you remember?
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No account · one minute