90Th232.04
Thorium (Th)
Element 90 · Actinide
Thorium (Th) is a chemical element with atomic number 90. It is classified as an actinide in period 7 of the periodic table (the f-block). Its standard atomic weight is 232.04 u and its ground-state electron configuration is [Rn] 6d² 7s².
Thorium facts
| Atomic number (Z) | 90 |
|---|---|
| Symbol | Th |
| Standard atomic weight | 232.04 u |
| Category | Actinide |
| Group | — (f-block) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 6d² 7s² |
| Electronegativity (Pauling) | 1.3 |
| State at 20 °C | Solid |
| Protons / electrons | 90 / 90 |
| Neutrons (most common isotope, approx.) | 142 |
| Molar mass | 232.04 g/mol |