In which one of the following compounds does the central atom obey the octet rule ?

Options

A. `XeF_(4)`
B. `XeOF_(2)`
C. `SCl_(2)`
D. `AlCl_(3)`

Explanation

To determine which compound has a central atom that obeys the octet rule, we will analyze each compound step by step. The octet rule states that atoms tend to form bonds until they are surrounded by eight valence electrons.

### Step 1: Analyze XEF4
1. **Valence Electrons Calculation**: Xenon (Xe) has 8 valence electrons. For XEF4, we have:
- Valence electrons = 8 (Xe) + 4 (F) = 12 electrons.
2. **Hybridization**:
- Hybridization = \( \frac{1}{2} \times \text{(number of valence electrons)} = \frac{1}{2} \times 12 = 6 \) → sp³d².
3. **Bonding and Lone Pairs**:
- 4 bond pairs (from 4 F atoms) and 2 lone pairs.
- Total electrons involved = 4 bonds × 2 electrons/bond + 2 lone pairs × 2 electrons/lone pair = 8 + 4 = 12 electrons.
4. **Conclusion**: The central atom (Xe) does not obey the octet rule as it has 12 electrons.

### Step 2: Analyze XEF2
1. **Valence Electrons Calculation**: For XEF2:
- Valence electrons = 8 (Xe) + 2 (F) = 10 electrons.
2. **Hybridization**:
- Hybridization = \( \frac{1}{2} \times 10 = 5 \) → sp³d.
3. **Bonding and Lone Pairs**:
- 3 bond pairs (from 2 F atoms) and 2 lone pairs.
- Total electrons involved = 3 bonds × 2 electrons/bond + 2 lone pairs × 2 electrons/lone pair = 6 + 4 = 10 electrons.
4. **Conclusion**: The central atom (Xe) does not obey the octet rule as it has 10 electrons.

### Step 3: Analyze SCL2
1. **Valence Electrons Calculation**: For SCL2:
- Valence electrons = 6 (S) + 2 (Cl) = 8 electrons.
2. **Hybridization**:
- Hybridization = \( \frac{1}{2} \times 8 = 4 \) → sp³.
3. **Bonding and Lone Pairs**:
- 2 bond pairs (from 2 Cl atoms) and 2 lone pairs.
- Total electrons involved = 2 bonds × 2 electrons/bond + 2 lone pairs × 2 electrons/lone pair = 4 + 4 = 8 electrons.
4. **Conclusion**: The central atom (S) obeys the octet rule as it has 8 electrons.

### Step 4: Analyze ALCL3
1. **Valence Electrons Calculation**: For ALCL3:
- Valence electrons = 3 (Al) + 3 × 7 (Cl) = 24 electrons.
2. **Hybridization**:
- Hybridization = \( \frac{1}{2} \times 24 = 12 \) → sp².
3. **Bonding and Lone Pairs**:
- 3 bond pairs (from 3 Cl atoms) and no lone pairs.
- Total electrons involved = 3 bonds × 2 electrons/bond = 6 electrons.
4. **Conclusion**: The central atom (Al) does not obey the octet rule as it has only 6 electrons.

### Final Conclusion
The only compound where the central atom obeys the octet rule is **SCL2**.

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