Which of the following halide does not exist

Options

A. Thalium (I) iodide
B. Thalium (III) iodide
C. Thalium (I) triiodide
D. Bis-aluminium (III) iodide

Explanation

To determine which halide does not exist among the given options, we need to analyze the oxidation states of thallium and aluminum in each compound. Let's go through the options step by step.

### Step 1: Understand the oxidation states of Thallium
Thallium (Tl) can exist in two oxidation states: +1 and +3. The +1 oxidation state is stable, while the +3 oxidation state is unstable due to the inert pair effect.

### Step 2: Analyze the first option - Thallium Iodide (TlI)
In Thallium Iodide, the oxidation state of thallium is +1, and the oxidation state of iodide (I) is -1. Since +1 is a stable oxidation state for thallium, TlI does exist.

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