Which of the following halide of group 13 elements does not exists:

Options

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

Explanation

To determine which halide of group 13 elements does not exist, we need to analyze the halides of the elements in this group: boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).

### Step-by-Step Solution:

1. **Identify Group 13 Elements**:
The elements in group 13 of the periodic table are boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).

2. **Understand Oxidation States**:
Group 13 elements can exhibit oxidation states of +1 and +3. However, as we move down the group from boron to thallium, the stability of the +3 oxidation state decreases due to the inert pair effect.

3. **Inert Pair Effect**:
The inert pair effect refers to the tendency of the s-electrons (in this case, the 6s electrons in thallium) to remain non-bonding and not participate in bonding as we move down the group. This results in a preference for the +1 oxidation state over the +3 oxidation state in heavier elements like thallium.

4. **Analyze Thallium Halides**:
- Thallium(I) iodide (TlI) exists because thallium can exhibit a +1 oxidation state.
- Thallium(III) iodide (TlI3) does not exist because thallium cannot effectively exhibit a +3 oxidation state due to the inert pair effect.

5. **Conclusion**:
Based on the analysis, the halide of thallium in the +3 oxidation state (TlI3) does not exist. Therefore, the answer to the question is that thallium(III) iodide does not exist.

### Final Answer:
Thallium(III) iodide (TlI3) does not exist.

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