Thulium (Tm)
Thulium is the chemical element with atomic number 69 and symbol Tm. It is a lanthanoid in period 6, with a standard atomic weight of 168.93 u.
Key facts
- Z
- 69
- Atomic weight
- 168.93 u
- Category
- lanthanoid
- State at 298 K
- Solid
- Occurrence
- primordial
- Discovered
- 1879
- CAS
- 7440-30-4
Measured properties
| Property | Value | Source |
|---|---|---|
| Electronegativity | 1.25 | National Center for Biotechnology Information (NIH) |
| Melting point | 1,818 K | National Center for Biotechnology Information (NIH) |
| Boiling point | 2,223 K | National Center for Biotechnology Information (NIH) |
| Density stp | 9.32 g/cm³ | National Center for Biotechnology Information (NIH) |
| Atomic radius empirical | 227 pm | National Center for Biotechnology Information (NIH) |
| Ionization energy 1st | 596.7 kJ/mol | National Center for Biotechnology Information (NIH) |
Electron configuration
- Noble gas notation
- [Xe] 4f¹³ 6s²
- Full notation
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹³ 5s² 5p⁶ 6s²
- Electrons per shell
- 2, 8, 18, 31, 8, 2