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thorium (Th)
A silvery-white radioactive metallic element , one of the actinides. Its chief ore is monazite. Thorium is tetravalent, resembling zirconium and hafnium. It is used in magnesium alloys and to produce uranium-233 for atomic fuel.
Thorium has 13 radioactive isotopes only one of which, thorium-232, occurs naturally.
The refractory thorium (IV) oxide was used to make incandescent gas mantles; it is added in small amounts to the tungsten filaments in electric lights.
| atomic number | 90 |
| relative atomic mass | 232.04 |
| relative density | 14.66 |
| melting point | 1,700°C (3,100°F) |
| boiling point | 4,000°C (7,200°F) |
Related categories
• ATOMIC AND NUCLEAR PHYSICS• INORGANIC CHEMISTRY
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