69Tm168.93
Thulium (Tm)
Element 69 · Lanthanide
Thulium (Tm) is a chemical element with atomic number 69. It is classified as a lanthanide in period 6 of the periodic table (the f-block). Its standard atomic weight is 168.93 u and its ground-state electron configuration is [Xe] 4f¹³ 6s².
Thulium facts
| Atomic number (Z) | 69 |
|---|---|
| Symbol | Tm |
| Standard atomic weight | 168.93 u |
| Category | Lanthanide |
| Group | — (f-block) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 4f¹³ 6s² |
| Electronegativity (Pauling) | 1.25 |
| State at 20 °C | Solid |
| Protons / electrons | 69 / 69 |
| Neutrons (most common isotope, approx.) | 100 |
| Molar mass | 168.93 g/mol |