85At210.000
Metalloidp-blockRadioactive
Astatine
Element 85 on the periodic table, symbol At, group 17, period 6.
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.
Appearance: unknown, probably metallic
Properties
- Atomic Number
- 85
- Atomic Mass
- 210.0000 u
- Group
- 17
- Period
- 6
- Block
- p-block
- Category
- Metalloid
- State at 25 °C
- Solid
- Melting Point
- 575 K · 301.9 °C
- Boiling Point
- 610 K · 336.9 °C
- Density
- 6.35 g/cm³
- Atomic Radius
- 127 pm
- Electronegativity
- 2.2
- Oxidation States
- -1, +1
- Abundance in Crust
- 3.00e-20 mg/kg
- Discovered
- 1940
- Discovered By
- Dale R. Corson
Electron Configuration
[Xe] 4f14 5d10 6s2 6p5
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p5
Ionisation Energies (kJ/mol)
- 1. 899.003
Elements near Astatine
Elements in the same group share the number of outer electrons and behave in similar ways. Elements in the same period share a shell, so they change steadily from left to right.