thorium
Sign in to saveThorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.
AI overview
Thorium is a naturally radioactive metal with a silvery appearance that turns olive-grey when exposed to air, and it's relatively soft with a high melting point. It's notable for being highly reactive—particularly when finely divided—and for having chemistry dominated by a specific oxidation state that makes it chemically active.
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Article
42 sectionsContents
- Bulk properties
- Isotopes
- Radiometric dating
- Chemistry
- Reactivity
- Inorganic compounds
- Coordination compounds
- Organothorium compounds
- Occurrence
- Formation
- Abundance
- On Earth
- History
- Erroneous report
- Discovery
- Initial chemical classification
- First uses
- Radioactivity
- Further classification
- Phasing out
- Nuclear power
- Nuclear weapons
- Production
- Concentration
- Acid digestion
- Alkaline digestion
- Purification
- Modern applications
- Potential use for nuclear energy
- Advantages
- Disadvantages
- Hazards and health effects
- Radiological
- Biological
- Chemical
- Exposure routes
- See also
- Explanatory notes
- Citations
- General and cited references
- Further reading
- External links
Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.
All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.0 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208Pb. On Earth, thorium and uranium are the only elements with no stable or nearly-stable isotopes that still occur naturally in large quantities as primordial elements. Thorium is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth elements.