81Tl
Thallium
Post-Transition MetalThallium (Tl) is element 81, a post-transition metal, in period 6 and group 13 of the periodic table. Its standard atomic weight is 204.38, it melts at 304 °C and boils at 1473 °C. Discovered by William Crookes, 1861.
Atomic Number81
SymbolTl
NameThallium
Atomic Weight204.38 u
CategoryPost-Transition Metal
Period6
Group13
Melting Point304 °C
Boiling Point1473 °C
Density11.85 g/cm³
Electron Config[Xe] 4f14 5d10 6s2 6p1
Discovered ByWilliam Crookes, 1861