The most common naturally occurring radioactive metal, thorium, is used inside vacuum tubes to allow an electric current to flow. It can also undergo nuclear fission, a process in which atoms split in two and release energy. Ways to make thorium-fueled nuclear reactors that produce electricity are being explored.
Summary of properties (Th)
| Atomic weight | 232.0377(4) |
| Discoverer (year) | Berzelius, Jöns Jacob (1829) |
| Natural form | metallic solid (face centered cubic) |
| Electron configuration | [Rn] 6d2 7s2 |
| Melting point (ºC) | 1750 |
| Boiling point (ºC) | 4790 |
| Abundance in earth's crust (ppm) | 9.6 |
| Isotope (abundance) | 232Th (100) |
| Density g/cm3 | 15.4 |
| Van der Waals radius (pm) | 245 |
| Covalent radius (pm) | 190 |
| Electronegativity (Pauling) | 1.3 |
| Vaporization enthalpy (kJ/mol) | 543.90 |
| Enthalpy of fusion (kJ/mol) | 13.81 |
| Specific heat capacity (J/g·K) at 25ºC and 1 atm | 0.11 |
| Thermal conductivity (W/cm·K) at 25ºC and 1 atm | 0.540 |
| Oxidation state | +4 |
| Electron affinity (eV) | |
| 1st Ionization potential (eV) | 6.3067 |
