The stability of monohalides of group `13` elements

Options

A. Increases down the group
B. Decreases down the group
C. First increases and then decreases
D. First decreases and then increases

Explanation

To analyze the stability of monohalides of group 13 elements, we can follow these steps:

### Step 1: Identify the Group 13 Elements
Group 13 elements include Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and Thallium (Tl).

### Step 2: Understand the Oxidation States
Group 13 elements can exhibit two common oxidation states: +1 and +3. The +3 oxidation state is typically more stable for lighter elements, while the +1 state becomes more stable for heavier elements.

### Step 3: Analyze the Stability of Oxidation States
- The stability of the +3 oxidation state decreases as we move down the group from Boron to Thallium.
- Conversely, the stability of the +1 oxidation state increases down the group.

### Step 4: Relate Oxidation States to Monohalides
Monohalides of group 13 elements can be represented as MX, where M is the group 13 element and X is the halogen. In these monohalides, the group 13 element is in the +1 oxidation state.

### Step 5: Conclude on the Stability of Monohalides
Since the stability of the +1 oxidation state increases down the group, we can conclude that the stability of monohalides (MX) of group 13 elements also increases down the group.

### Final Answer
The stability of monohalides of group 13 elements increases down the group.

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