Element 85
Astatine (At)
Astatine (At) is element 85 of the periodic table, a halogen in period 6, group 17 (p-block) with an atomic mass of 210 and is a solid at standard conditions.
At a glance
- Atomic number
- 85
- Symbol
- At
- Atomic mass
- 210 u
- Category
- Halogens
- Period
- 6
- Group
- 17
- Block
- p-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
- Shorthand configuration
- [Xe] 4f14 5d10 6s2 6p5
- Electrons per shell
- 2, 8, 18, 32, 18, 7
- Oxidation states
- -1, +1, +3, +5, +7
Physical properties
- Melting point
- 575 K
- Boiling point
- 610 K
- Density
- 7 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 2.2
- Atomic radius
- 127 pm
- Covalent radius
- 150 pm
- Van der Waals radius
- 202 pm
- First ionization energy
- 920 kJ/mol
- Electron affinity
- 233 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| At-210 | 209.98715 | — | Half-life 8.1 hours |
Common uses
- Cancer treatment research
- Scientific research
Discovery
- Year
- 1940
- Discovered by
- Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè
- Country
- USA