At
Astatine
Element 85 · Halogen
Astatine (At)
Astatine is the rarest naturally occurring element in Earth’s crust. Less than 30 grams exist at any moment.
- Halogen
- Period 6
- Group 17
- p-block
- solid at room temperature
- ☢ Radioactive
Key properties
- Atomic mass
- [210]
- u
- Electron configuration
- [Xe] 4f14 5d10 6s2 6p5
- Melting point
- 301.9 °C
- 575 K
- Boiling point
- 336.9 °C
- 610 K
- Density
- 7 g/cm³
- Electronegativity
- 2.2
- Pauling
- Atomic radius
- 202 pm
- van der Waals
- 1st ionisation energy
- 9.5 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about astatine
- 01
It was first made by bombarding bismuth with alpha particles at Berkeley.
- 02
No visible amount of astatine has ever been collected — it would vaporise from its own heat.
- 03
Astatine-211 is being studied for targeted alpha therapy against cancer.
Applications
What is astatine used for?
- Research in targeted cancer therapy
History
Discovery & name origin
Discovered by
Year
Where
United States
Name origin
Greek astatos, “unstable”.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 85
- Atomic mass
- [210] u
- Group
- 17
- Period
- 6
- Block
- p-block
- Electron configuration
- [Xe] 4f14 5d10 6s2 6p5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p5
- Electrons per shell
- 2, 8, 18, 32, 18, 7
- Electronegativity (Pauling)
- 2.2
- Electron affinity
- 2.8 eV
- Atomic radius (van der Waals)
- 202 pm
- Stable isotopes
- None — all isotopes are radioactive
Oxidation states
Highlighted: common oxidation states (+7, +5, +3, +1, -1).
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 575 K · 301.9 °C · 575.3 °F
- Boiling point
- 610 K · 336.9 °C · 638.3 °F
- Density
- 7 g/cm³
- Molar heat capacity
- —
- Appearance
- Unknown, probably metallic
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Astatine questions
What is At on the periodic table?
At is the symbol for astatine, element 85 on the periodic table. It sits in group 17, period 6, in the halogen category, and has an atomic mass of [210].
What is the atomic number of astatine?
Astatine has atomic number 85, so every astatine atom has 85 protons in its nucleus. Its symbol is At and its atomic mass is [210].
Who discovered astatine?
Astatine was discovered by Dale R. Corson, Kenneth Ross MacKenzie and Emilio Segrè in 1940 (United States). The name comes from Greek astatos, “unstable”.
What is astatine used for?
Astatine is used for: research in targeted cancer therapy.
Is astatine a metal?
No. Astatine is classed as a halogen.
What is the electron configuration of astatine?
The electron configuration of astatine is [Xe] 4f14 5d10 6s2 6p5. Its 85 electrons are arranged in shells as 2, 8, 18, 32, 18, 7.