Th
232.040Thorium
Toryum
Thorium is a radioactive actinide with atomic number 90. It is known for thorium-232, the thorium fuel cycle to uranium-233, thoria ceramics, Welsbach gas mantles, thoriated tungsten electrodes and Thorotrast history.
90
232.04 g/mol
[Rn] 6d² 7s²
2 | 8 | 18 | 32 | 18 | 10 | 2
1.3
11.72 g/cm³
1841.8 °C
4787.9 °C
Jöns Jacob Berzelius
Thorium was discovered in 1829 by Jöns Jacob Berzelius in a Norwegian mineral and named after Thor, the Norse god of thunder. Thorium minerals such as monazite are important natural sources.
Thorium-230
Half-life: About 75,400 years. Natural uranium-series isotope used in U-Th dating contexts.Thorium-232
Natural abundance: Nearly 100%. Half-life: About 1.4 x 10¹⁰ years. Main natural thorium isotope and fertile material for the thorium fuel cycle.ThO₂
Thorium DioxideHigh-temperature ceramic, historical gas mantle material and nuclear fuel research material.ThF₄
Thorium(IV) FluorideOptical coating and molten-salt reactor research compound.ThSiO₄
ThoriteThorium silicate mineral and historical source material.- Thorium fuel cycle research, where thorium-232 can breed fissile uranium-233
- Thorium dioxide ceramics with very high melting point
- Historical Welsbach gas mantles made from thorium and cerium oxides
- Thoriated tungsten welding electrodes, now often replaced by safer alternatives
- Thorium fluoride and oxide optical or high-temperature material research
Thorium has no biological role. Thorium-232 is a long-lived alpha emitter, and inhaled thorium compounds or historical Thorotrast exposure can pose serious health risks.
- Thorium is more abundant in Earth’s crust than uranium, but it is not directly fissile.
- In the thorium fuel cycle, Th-232 absorbs a neutron and ultimately produces fissile U-233.
- Welsbach mantles helped make gas lighting much brighter before electric lighting became dominant.
- Thorotrast, a historical thorium dioxide contrast agent, was abandoned after long-term cancer risks became clear.
- Thorium has atomic number 90 and symbol Th.
- Its electron configuration is [Rn] 6d² 7s².
- The common oxidation state is +4.
- Remember thorium for Th-232, U-233 breeding and the thorium fuel cycle.
What is the atomic number of thorium?
The atomic number of thorium is 90.
What is the electron configuration of thorium?
Thorium has the electron configuration [Rn] 6d² 7s².
What is thorium used for?
Thorium is used or studied in nuclear fuel cycles, high-temperature ceramics, historical gas mantles, thoriated electrodes and optical materials.
What is the thorium fuel cycle?
The thorium fuel cycle uses fertile thorium-232 to produce fissile uranium-233 after neutron capture and beta decays.
Is thorium radioactive?
Yes. Natural thorium is dominated by thorium-232, a long-lived alpha-emitting isotope.
Is thorium more abundant than uranium?
Thorium is generally more abundant in Earth’s crust than uranium, often cited at about three to four times as abundant.