85At209.98715
Astatine
Halogen
Solid at STP
Period 6Group 17Block PDiscovered 1940
[Xe]6s2 4f14 5d10 6p5
Astatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.
📖 Read more on Wikipedia →Atomic Properties
| Atomic Number | 85 |
| Atomic Mass | 209.98715 u |
| Electron Configuration | [Xe]6s2 4f14 5d10 6p5 |
| Oxidation States | 7, 5, 3, 1, -1 |
| Electronegativity | 2.2 (Pauling) |
| Atomic Radius | 202 pm |
| Ionization Energy | 9.5 eV |
| Electron Affinity | 2.8 eV |
| Block | P |
Physical Properties
| Appearance | unknown, probably metallic |
| Standard State | Solid |
| Melting Point | 575 K (301.9 °C) |
| Density | 7 g/cm³ |
| CPK Color | #754F45 |
Classification
| Category | Halogen |
| Group Block | Halogen |
| Period | 6 |
| Group | 17 |
| Block | P |
Discovery
| Year Discovered | 1940 |
| Discovered By | Dale R. Corson |
| Electron Shells | 2, 8, 18, 32, 18, 7 |