Which of the following oxides is most alkaline in nature?

Options

A. `B_2O_3`
B. `Al_2O_3`
C. `In_2O_3`
D. `Tl_2O`

Answer

To determine which of the given oxides is most alkaline in nature, we can follow these steps:

### Step 1: Identify the Oxides
We have the following oxides to consider:
1. B2O3 (Boron oxide)
2. Al2O3 (Aluminum oxide)
3. In2O3 (Indium oxide)
4. Tl2O (Thallium oxide)

### Step 2: Classify the Oxides
Next, we need to classify these oxides based on the metallic character of the central atom:
- Boron (B) is a non-metal.
- Aluminum (Al), Indium (In), and Thallium (Tl) are metals.

### Step 3: Understand Alkaline Nature
Metal oxides are generally alkaline in nature, while non-metal oxides are acidic. The more metallic the element, the more alkaline its oxide tends to be.

### Step 4: Analyze Metallic Character
As we move down a group in the periodic table, the metallic character increases. This means:
- Thallium (Tl) has a higher metallic character than Indium (In), which has a higher metallic character than Aluminum (Al), and Boron (B) is the least metallic.

### Step 5: Determine Alkaline Nature Order
Based on the metallic character, we can arrange the oxides in order of increasing alkaline nature:
1. B2O3 (least alkaline, non-metal oxide)
2. Al2O3
3. In2O3
4. Tl2O (most alkaline)

### Conclusion
Thus, the oxide that is most alkaline in nature is **Tl2O (Thallium oxide)**.

### Answer
**Option D: Tl2O (Thallium oxide) is the correct answer.**

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