Thorium (Th) - Element 90 | Properties & Electron Configuration
What is Thorium?
Thorium (Th) is element 90, a actinide in period 7. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d² 7s².
| Atomic Number | 90 |
| Symbol | Th |
| Atomic Mass | 232.04 u |
| Category | Actinide |
| Period | 7 |
| Group | N/A (f-block) |
| Block | f |
| Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d² 7s² |
| Short Config | [Rn] 6d² 7s² |
| Electronegativity | 1.3 |
| Atomic Radius | 180 pm |
| Ionization Energy | 587 kJ/mol |
| Electron Affinity | N/A |
| Phase (STP) | Solid |
Electron Configuration
The full electron configuration of Thorium is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d² 7s². In noble gas shorthand, this is written as [Rn] 6d² 7s².
Thorium is a f-block element, period 7.
Periodic Trends
Electronegativity: Thorium has a Pauling electronegativity of 1.3.
Atomic Radius: 180 pm. Across period 7, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 587 kJ/mol. Ionization energy generally increases across a period and decreases down a group.
View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.
Explore Thorium on the Interactive Periodic Table