| Thallium ✕ | |
|---|---|
| Symbol | Tl |
| Atomic number | 81 |
| Chemical property | Post-transition metal |
| Origin o the name | the Greek thallos, 'green twig' |
| Group | 13 |
| Period | 6 |
| Atomic weight (u) | 204.38 |
| Density (g/cm³) | 11.85 |
| Melting point (K) | 577 |
| Boiling point (K) | 1746 |
| Heat capacity (J/(g·K)) | 0.129 |
| Electro-negativity | 1.62 |
| Abundance in earth's crust (mg/kg) | 0.85 |