Thorium: the essentials
Thorium is a source of nuclear power. There is probably more untapped energy available for use from thorium in the minerals of the earth's crust than from combined uranium and fossil fuel sources. Much of the internal heat the earth has been attributed to thorium and uranium.
When pure, thorium is a silvery white metal which is air-stable and retains its lustre for several months. When contaminated with the oxide, thorium slowly tarnishes in air, becoming grey and finally black. Thorium oxide has a melting point of 3300°C, the highest of all oxides. Only a few elements, such as tungsten, and a few compounds, such as tantalum carbide, have higher melting points.
Thorium is slowly attacked by water, but does not dissolve readily in most common acids, except hydrochloric. Powdered thorium metal is often pyrophoric and should be carefully handled.When heated in air, thorium turnings ignite and burn brilliantly with a white light.
Thorium is named for Thor, the Scandinavian god of war. It is found in thorite and thorianite in New England (USA) and other sites.
- Name: thorium
- Symbol: Th
- Atomic number: 90
- Relative atomic mass (Ar): 232.03806 (2) [see note g]
- Standard state: solid at 298 K
- Colour: silvery white
- Classification: Metallic
- Group in periodic table:
- Group name: Actinoid
- Period in periodic table: 7 (actinoid)
- Block in periodic table: f-block
- Electron shell structure: 2.8.18.32.18.10.2
- CAS Registry ID: 7440-29-1
Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Thorium: historical information
Thorium was discovered by Berzelius in 1828 in a mineral given to him by the Reverend Has Morten Thrane Esmark.
Thorium around us Read more »
Thorium has no biological role.
Thorium is recovered commercially from the mineral monazite sand (a mixture of calcium, cerium, thorium, and other rare earth metal phosphates). It is found in thorite and thorianite (thorium oxide, ThO2) in New England (USA) and elsewhere. Much of the earth's internal heat has been attributed to thorium and uranium. There may be more energy available for use from thorium in the minerals of the earth's crust than from all combined uranium and fossil fuel sources.
| Location | ppb by weight | ppb by atoms | Links |
|---|---|---|---|
| Universe | 0.4 | 0.002 | 
|
| Crustal rocks | 6000 | 540 | 
|
| Human | (no data) ppb by weight | (no data) atoms relative to C = 1000000 | 
|
Physical properties Read more »
Density of solid: 11724 kg m-3
Molar volume: |196| cm3
Thermal conductivity: |206| W m‑1 K‑1
Heat properties Read more »
Melting point: 2115 [1750 °C (3182 °F)] K
Boiling point: 5093 [4820 °C (8708 °F)] K
Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of thorium is: ccp (cubic close-packed).
Thorium: orbital properties Read more »
Thorium atoms have 90 electrons and the shell structure is 2.8.18.32.18.10.2. The ground state electronic configuration of neutral Thorium is [Rn].6d2.7s2 and the term symbol of Thorium is 3F2.
Pauling electronegativity: 1.3 (Pauling units)
First ionisation energy: 587 kJ mol‑1
Second ionisation energy: 1110 kJ mol‑1
Isolation
Isolation: coming soon!
Thorium isotopes Read more »
| Isotope | Mass /Da |
Natural abund. (atom %) |
Nuclear spin (I) |
Nuclear magnetic moment (μ/μN) |
|---|---|---|---|---|
| 232Th | 100 | 0 |
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