Symbol Name Atomic Number Atomic Weight Group Number
Tl Thallium 81 204.3833 13


Standard State: solid at 298 K
Color: Silvery white

Thallium was discovered spectroscopically in 1861 by Crooke. The element was named after the beautiful green spectral line which identified the element.  The metal isolated by both Crookes and Lamy in 1862 about the same time. Thallium occurs in crooksite, lorandite, and hutchinsonite.   It is also present in pyrites and is recovered from the roasting of the ore in connection with the production of sulfuric acid. Manganese nodules, found on the ocean floor, contain thallium.  Thallium sulfate has been widely employed as a rodenticide and ant killer.  It is odorless tasteless, and give no warning of its presence.  Thallium has been used in treating ringworm and other  skin infections, however its use has been limited because of the narrow margin between toxicity and therapeutic benefits.