Astatine (At)
Astatine (At) is element 85, a halogen. Atomic mass 210, configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵. Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 85 |
|---|---|
| Symbol | At |
| Standard atomic weight | 210 |
| Category | Halogen |
| Group | 17 |
| Period | 6 |
| State at room temperature | Solid |
| Electron configuration | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵ |
| Valence electrons | 7 |
| Common oxidation states | -1, +1 |
| Common ions | No common ions |
| Electronegativity (Pauling) | 2.2 |
| First ionization energy | 899 kJ/mol |
| Electron affinity | 233.1 kJ/mol |
| Melting point | ~302°C |
| Boiling point | ~350°C |
Common uses
- Medical research only (rarest natural element)
Where it matters
- Targeted Alpha Therapy (Cancer treatment research)
Hazards
- Highly radioactive
History
| Discovered | 1940 |
|---|---|
| Discovered by | Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè |
| Name | From Greek astatos (unstable) |