Element 90
Thorium (Th)
Thorium (Th) is element 90 of the periodic table, a actinide in period 7 (f-block) with an atomic mass of 232.04 and is a solid at standard conditions.
At a glance
- Atomic number
- 90
- Symbol
- Th
- Atomic mass
- 232.04 u
- Category
- Actinides
- Period
- 7
- Block
- f-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d2 7s2
- Shorthand configuration
- [Rn] 6d2 7s2
- Electrons per shell
- 2, 8, 18, 32, 18, 10, 2
- Oxidation states
- +1, +2, +3, +4
Physical properties
- Melting point
- 2115 K
- Boiling point
- 5061 K
- Density
- 11.72 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1.3
- Atomic radius
- 180 pm
- Covalent radius
- 206 pm
- First ionization energy
- 587 kJ/mol
- Electron affinity
- 113 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Th-232 | 232.03806 | — | Half-life 14 billion years |
Common uses
- Nuclear fuel research
- Gas mantles
- Welding electrodes
- Optics
Discovery
- Year
- 1829
- Discovered by
- Jöns Jacob Berzelius
- Country
- Sweden