Astatine

Astatine (atomic number 85) is what happens in nature when that naughty radioactive misfit of the actinide series, uranium, decays. The least unstable naturally occurring isotope is 219, with a half life of 0.9 minutes, though that of the artificially created 210 is 8.3 hours. Shell structure is 2.8.18.32.18.7; ground state configuration is Xe.4f¹⁴.5d¹⁰.6s².6p⁵
Fat chance any visible amount will ever be created, making astatine one of the kung-fu space ninjas of the chemical world, leaving chemists puzzling and making half-assed guesses about its chemical properties in its non-existent wake.

Astatine
Symbol: At
Atomic Number: 85
Atomic Weight: 210 (most stable)
Boiling Point: 610 K
Melting Point: 575 K
Density at 300K: ??? g/cm³
Covalent radius: 1.47
Atomic radius: 1.43
Atomic volume: ??? cm³/mol
First ionization potental: ??? V
Specific heat capacity: ??? Jg^-1K^-1
Thermal conductivity: 1.7 Wm^-1K^-1
Electrical conductivity: ???*10⁶Ω^-1m^-1
Heat of fusion: 12 kJ/mol
Heat of vaporization: 30 kJ/mol
Electronegativity: 2.2 (Pauling's)

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