Thulium (Tm)
Thulium (Tm) is element 69, a lanthanide. Atomic mass 168.934219, configuration [Xe] 4f¹³ 6s². Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 69 |
|---|---|
| Symbol | Tm |
| Standard atomic weight | 168.934219(5) |
| Category | Lanthanide |
| Period | 6 |
| State at room temperature | Solid |
| Electron configuration | [Xe] 4f¹³ 6s² |
| Valence electrons | 2 (Variable) |
| Common oxidation states | +3 |
| Common ions | No common ions |
| Electronegativity (Pauling) | 1.25 |
| First ionization energy | 597 kJ/mol |
| Electron affinity | 99.28 kJ/mol |
| Atomic radius | 175 pm |
| Density | 9.32 g/cm³ |
| Melting point | 1549°C |
| Boiling point | 1950°C |
| Specific heat | 0.16 J/(g·°C) |
Natural isotopes
- Tm-169: Stable
Common uses
- Portable X-ray machines
- Lasers
- Euro banknotes
Where it matters
- Portable X-rays (Tm-170 source)
Hazards
- Low toxicity
History
| Discovered | 1879 |
|---|---|
| Discovered by | Per Teodor Cleve |
| Name | From Thule (mythical North) |