Actinium (Ac)
Actinium (Ac) is element 89, an actinide. Atomic mass 227, configuration [Rn] 6d¹ 7s². Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 89 |
|---|---|
| Symbol | Ac |
| Standard atomic weight | 227 |
| Category | Actinide |
| Period | 7 |
| State at room temperature | Solid |
| Electron configuration | [Rn] 6d¹ 7s² |
| Valence electrons | 2 (Variable) |
| Common oxidation states | +3 |
| Common ions | No common ions |
| Electronegativity (Pauling) | 1.1 |
| First ionization energy | 499 kJ/mol |
| Electron affinity | 33.77 kJ/mol |
| Atomic radius | 195 pm |
| Density | 10 g/cm³ |
| Melting point | 1051°C |
| Boiling point | 3198°C |
| Specific heat | 0.12 J/(g·°C) |
Common uses
- Neutron source
- Immunotherapy (Ac-225)
Where it matters
- Targeted Alpha Therapy (TAT) for cancer
Hazards
- Highly radioactive
History
| Discovered | 1899 |
|---|---|
| Discovered by | André-Louis Debierne |
| Name | Greek aktis (ray) |