Atomic Number 81     Atomic Mass 204.38     Density 11.85 g/mL

State solid     Color silvery white     Electronegativity 2.33

Melting Point 303.5°C     Boiling Point 1457°C

Natural Isotopes Tl-203 29.524%   Tl-205 70.476%

Abbreviated Electron Configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹

Discovered by Sir William Crookes in 1861.