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Thulium (Tm)
Atomic number 69 · Lanthanide
| Atomic number | 69 |
|---|---|
| Atomic mass | 168.93422 u |
| Molar mass | 168.93422 g/mol |
| Category | Lanthanide |
| Group / period / block | — / 6 / f |
| Electron configuration | [Xe] 4f13 6s2 |
| Electrons per shell | 2, 8, 18, 31, 8, 2 |
| Electronegativity (Pauling) | 1.25 |
| Atomic radius | 175.0 pm |
| Density | 9.321 g/cm³ |
| First ionisation energy | 6.1844 eV |
| Melting point | 1818.15 K (1545.00 °C) |
| Boiling point | 2223.15 K (1950.00 °C) |
| Common oxidation states | +3 |
| Abundance in Earth's crust | 0.52 ppm |
Uses
Portable X-ray machines, lasers
Discovery
1879, Per Theodor Cleve