Astatine (At)

From Wikipedia, the free encyclopediaAstatine 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.

Astatine in the periodic table

SymbolAt
Atomic number85
Group17
Period6
Blockp
Element categoryMetalloid

Physical properties

Phase at STPSolid
Density6.35 g/cm3
Atomic weight210 u
Melting point575 K
301.85 °C
575.33 °F
Boiling point610 K
336.85 °C
638.33 °F

Atomära egenskaper

Electronegativity (Pauling Scale)2.2
Electron affinity233 kJ/mol
Ionization energies
1899.003 kJ/mol

Electron configuration

Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
Electrons per shell2, 8, 18, 32, 18, 7

History

Discovered1940
Discovered byDale R. Corson
Kenneth Ross MacKenzie
Emilio Segrè