85At[210]
Astatine (At)
Element 85 · Halogen
Astatine (At) is a chemical element with atomic number 85. It is classified as a halogen in period 6, group 17 of the periodic table (the p-block). Its most stable known isotope has mass number 210 and its ground-state electron configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵.
Astatine facts
| Atomic number (Z) | 85 |
|---|---|
| Symbol | At |
| Mass number of most stable isotope | [210] |
| Category | Halogen |
| Group | 17 |
| Period | 6 |
| Block | p-block |
| Electron configuration | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵ |
| Electronegativity (Pauling) | 2.2 |
| State at 20 °C | Solid |
| Protons / electrons | 85 / 85 |
| Neutrons (most common isotope, approx.) | 125 |
| Molar mass | 210 g/mol |