Thorium
A weakly radioactive metal studied as a nuclear fuel.
Inside the Thorium atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Thorium atom step by step.
Electron configuration
[Rn] 6d2 7s2
A neutral Thorium atom has 90 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 2115 K (1842 °C)
- Boiling point
- 5061 K (4788 °C)
- Density
- 11.72 g/cm³
- Electronegativity
- 1.3 Pauling
- Atomic radius
- 180 pm
- 1st ionization energy
- 587 kJ/mol
- Category
- Actinides
Discovery & naming
- Discovered
- 1829
- Discovered by
- Jöns Jacob Berzelius
- Origin of name
- Thor, the Norse god of thunder.
Notable uses
A potential nuclear fuel and old gas-lamp mantles.
Where Thorium comes from
Neutron star mergers
An r-process element with a half-life comparable to the age of the universe, which is why any survives at all.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 90
- Atomic mass
- 232.04
- Category
- Actinides
- Group · Period
- — · 7
- Block
- f-block
- Shells
- 2 · 8 · 18 · 32 · 18 · 10 · 2