81 Tl 204.38
Thallium
POST-TRANSITION METAL
Phase: Solid
Discovered: William Crookes
Block: P
Summary
Thallium is a chemical element with symbol Tl and atomic number 81. This soft gray post-transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.
Source: WikipediaPhysical Properties
Atomic Mass 204.38 u
Density 11.85 g/cm³
Melting Point 577 K
Boiling Point 1746 K