THORIUM
TRANSITION ELEMENT: ACTINIDE
| Atomic number: | 90 |
| Group numbers: | 3 |
| Period: | 7 |
| Electronic configuration: | [Rn] 6d2 7s2 |
| Formal oxidation number: | +4 |
| Electronegativities: | 1.3 |
| Atomic radius / pm: | 179.8 |
| Relative atomic mass: | 232.0377(4) |
Thorium was discovered by Jöns Jacob Berzelius (SE) in 1828. Named after Thor, the mythological Scandinavian god of war. It is a heavy, grey, soft, malleable, ductile, radioactive metal that tarnishes in air and reacts with water. It reacts violently with oxidants. Thorium is found in various minerals like monazite and thorite. It is used in making strong alloys, in ultraviolet photoelectric cells. It is a common ingredient in high-quality lenses. When bombarded with neutrons thorium creates uranium-233, a nuclear fuel. The price of 99.8 % pure thorium powder is 464.20 € for 10 g.
| Density / g dm-3: | 11720 | (293 K) |
| Molar volume / cm3mol-1: | 19.80 | (293 K) |
| Electrical resistivity / µΩcm: | 13 | (20 °C) |
| Thermal conductivity / W m-1K-1: | 54 |
| Melting point / °C: | 1750 |
| Boiling point / °C: | 4788 |
| Heat of fusion / kJ mol-1: | 19.2 |
| Heat of vaporization / kJ mol-1: | 513.67 |
| Heat of atomization / kJ mol-1: | 598.65 |
| First ionization energy / kJ mol-1: | 608.51 |
| Second ionization energy / kJ mol-1: | 1109.59 |
| Third ionization energy / kJ mol-1: | 1929.72 |
| in the atmosphere / ppm: | - |
| in the Earth's crust / ppm: | 3.5 |
| in the oceans / ppm: | 0.0007 |
| Crystal structure: | face-centered cubic |
| Unit-cell dimensions / pm: | a=508.42 |
| Space group: | Fm3m |
| Isotope | Relative atomic mass | Mass percent (%) |
|---|---|---|
| 230Th | 230.033 13(2) | * |
| 232Th | 232.038 06(2) | 100 |
| Balanced half-reaction | Eo / V | |
|---|---|---|
| Th4+ + 4e- → Th(s) | - 1.90 | |
| Th(OH)4(s) + 4e- → Th(s) + 4OH- | - 2.48 |
| 89 Actinium | ← | 90 Thorium | → | 91 Protactinium |
Citing this page:
Generalic, Eni. "Thorium." EniG. Periodic Table of the Elements. KTF-Split, 18 Jan. 2024. Web. {Date of access}. <https://www.periodni.com/th.html>.
