Thallium halide facts for kids

The thallium halides are special chemical compounds. They are made when the element thallium joins with elements like fluorine, chlorine, bromine, or iodine. Thallium can act in two main ways when it forms these compounds. This is called its "oxidation state." It can be in a +1 state or a +3 state.

Thallium Monohalides: The +1 Team

This image shows the structure of thallium(I) iodide. It looks like a distorted salt crystal.

These compounds have thallium in its +1 oxidation state. This means each thallium atom has "given away" one electron.

• Thallium(I) fluoride is a white crystal. It can dissolve in water easily. This is different from the other thallium monohalides.
• Thallium(I) chloride is a white crystal. It changes when exposed to light.
• Thallium(I) bromide is a pale yellow crystal. It also reacts to light.
• Thallium(I) iodide is a yellow crystal at room temperature. If you heat it up, its color changes to red.

Thallium Trihalides: The +3 Team

Thallium(III) halides are not very common. Some of them are not very stable, meaning they can break down easily. For example, thallium(III) iodide does not even form. These compounds are quite different from similar ones made with elements like aluminum or gallium.

• Thallium(III) fluoride is also called thallic fluoride. It is made of thallium in its +3 oxidation state and fluoride ions. Scientists make it by mixing thallium(III) oxide with other chemicals like bromine trifluoride or fluorine, usually when it's warm.
• Thallium(III) chloride is also known as thallic chloride. It contains thallium in its +3 oxidation state and chloride ions. If you heat it above 40°C, it breaks down. It turns into thallium(I) chloride and chlorine gas. You can make it by reacting thallium(I) chloride with chlorine in a special liquid called an organic solution.
• Thallium(III) bromide is also called thallic bromide. It has thallium in its +3 oxidation state and bromide ions. It breaks down easily at low temperatures. It turns into thallium(I) bromide and bromine. You can create it by reacting thallium(I) bromide with bromine in water or an organic solution.
• Thallium(I) triiodide is a black crystal. Even though it's called "triiodide," it doesn't actually contain thallium in the +3 state. Instead, it has a special shape that includes a linear I₃^- ion.