NO. 085Halogen

At

Astatine

Astatine is the rarest naturally occurring halogen and is extremely radioactive. Its chemistry is poorly understood due to its scarcity and short-lived isotopes.

Crystal Structure

Face-centered cubic (fcc)

Technical Specifications

Atomic Mass210 u

Density7 g/cm³

Melting Point575 K

Boiling Point610 K

Atomic Radius127 pm

Electronegativity2.2

Ionization Energy920 kJ/mol

Electron Affinity270 kJ/mol

Bonding TypeCovalent

Oxidation States-1, 1, 3, 5, 7

Acid/BaseCan act as acid or base

ReactivityHigh

Electron Configuration

[Xe] 4f14 5d10 6s2 6p5

Discovered ByDale R. Corson

Year1940

Known Isotopes

At-210At-211