Thallium halide

The thallium halides come in two oxidation states: monohalides, where thallium has the oxidation state +1, and trihalides, where thallium generally has oxidation state +3.
Monohalides.
The monohalides all contain thallium with oxidation state +1.
Trihalides.
Thallium(III) halides are very rare. Some of them are unstable. The thallium(III) iodide does not form. They are quite different to aluminium, gallium and indium trihalides.