Element Thorium
It is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point.
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90.
Names and Identifiers
| Chemical Formula: | Th |
| CAS: | 7440-29-1 |
| Molecular Weight: | 232.03800 g/mol |
| EC Number : | 231-139-7 |
| MDL Number: | n/a |
| Color: | silvery-white |
| Other Names: | n/a |
| PubChem CID: | 23960 |
| IUPAC Name: | Thorium |
| Inchl: | InChI=1S/Th |
| InChI Key: | ZSLUVFAKFWKJRC-UHFFFAOYSA-N |
| Canonical SMILES: | [Th] |
| ICSC Number: | 0337 |
Physical & Chemical Properties
| Phase: | Solid |
| Density: | 11.7 g/cm³ |
| Boiling Point: | 5061 K (4788 °C, 8650 °F) |
| Melting Point: | 2023 K (1750 °C, 3182 °F) |
| Molecular Formula: | Th |
| Flash Point: | n/a |
| Exact Mass: | 232.03800 |
| Symbol: |     |
| Signal Word: | Danger |
| Hazard Statements: | H272-H301-H373-H315-H319-H335 |
| Precautionary Statements: | P210 |
| Hazard Codes: | n/a |
| Risk Phrases: | n/a |
| Safety Phrases: | n/a |
| RIDADR: | n/a |
| WGK Germany: | 3 |
| RTECS: | n/a |
| Packaging Group: | n/a |
| Hazard Class: | n/a |
All but two elements up to bismuth (element 83) have an isotope that is practically stable for all purposes (“classically stable”), with the exceptions being technetium and promethium (elements 43 and 61).
Naturally occurring isotopes
| Isotope | Mass/Da | Natural abundance (atom %) | Nuclear spin (I) | Magnetic moment (μ/μN) |
|---|---|---|---|---|
| 232Th | 100 | 0 |
Radiosotope data
| Isotope | Mass/Da | Half-life | Mode of decay | Nuclear spin | Nuclear magnetic moment |
|---|---|---|---|---|---|
| 227Th | 227.027699 | 18.72 d | α to 223Ra | 3/2 | |
| 228Th | 228.028731 | 1.913 y | α to 224Ra; 20O | 0 | |
| 229Th | 229.031754 | 7900 y | α to 225Ra | 5/2 | 0.46 |
| 230Th | 230.033126 | 75400 y | α to 226Ra; SF | 0 | |
| 231Th | 231.036296 | 1.063 d | α to 227Ra; β– to 231Pa | 5/2 | |
| 232Th | 232.0380508 (23) | 1.4 x 1010 y | α to 228Ra; SF | 0 | |
| 233Th | 233.041576 | 22.3 m | β– to 233Pa | 1/2 | |
| 234Th | 234.036596 | 24.10 d | β– to 234Pa | 0 |