Which halides of the element of group `13` do not exist as dimer in the vapour state, the element is

Options

A. Al
B. B
C. Ga
D. Tl

Answer

To determine which halides of the elements in Group 13 do not exist as dimers in the vapor state, we will analyze each element in the group and their respective halides.

### Step 1: Identify the Group 13 Elements
The elements in Group 13 are:
- Boron (B)
- Aluminum (Al)
- Gallium (Ga)
- Indium (In)
- Thallium (Tl)

### Step 2: Examine the Halides of Each Element
1. **Boron (B)**: The primary halide is boron trichloride (BCl3). Boron does not form dimers in the vapor state due to its small size and the nature of its bonding.

2. **Aluminum (Al)**: Aluminum halides, such as aluminum chloride (AlCl3), exist as dimers in the vapor state. In the vapor phase, AlCl3 exists as a dimer (Al2Cl6).

3. **Gallium (Ga)**: Gallium halides, like gallium chloride (GaCl3), also exist as dimers in the vapor state.

4. **Indium (In)**: Indium halides, such as indium chloride (InCl3), exist as dimers in the vapor state.

5. **Thallium (Tl)**: Thallium halides, including thallium chloride (TlCl3), also exist as dimers in the vapor state.

### Step 3: Conclusion
From the analysis, we can conclude that:
- The only halide that does not exist as a dimer in the vapor state is that of **Boron (B)**, specifically BCl3.

### Final Answer
The halide of the element of Group 13 that does not exist as a dimer in the vapor state is **Boron (B)**.

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