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Astatine
Element 85 · 209.98715 u
Astatine is the rarest naturally occurring element on Earth.
Physical Properties
| Atomic Mass | 209.98715 u |
| Density | 7.0 g/cm³ |
| Melting Point | 575.0 K |
| Boiling Point | 610.0 K |
| Appearance | Likely metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 2.2 (Pauling) |
| 1st Ionization Energy | 899.0 kJ/mol |
| Electron Affinity | 270.1 kJ/mol |
| Oxidation States | -1, +1, +3, +5, +7 |
Atomic Properties
| Electron Configuration | [Xe] 4f14 5d10 6s2 6p5 |
| Atomic Radius | 150.0 pm |
| Covalent Radius | 150.0 pm |
| Van der Waals Radius | 202.0 pm |
Discovery
| Discovered By | Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segre |
| Discovery Year | 1940 |
| Location | Berkeley, California, USA |
| Named After | Greek 'astatos' meaning unstable |
About Astatine
Astatine is extremely rare, radioactive, and the heaviest known halogen. Less than 30 grams exist in Earth's crust at any time. It has never been seen in bulk.
Uses & Applications
Potential targeted cancer therapy (astatine-211), still experimental.
Fun Fact
Astatine has never been seen with the naked eye -- there is less than 30 grams in the entire Earth at any moment.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 209 | - | 5.41 hours | No |
| 210 | - | 8.1 hours | No |
| 211 | - | 7.214 hours | No |
Electron Configuration
[Xe] 4f14 5d10 6s2 6p5