The change in hybridization of aluminium when `Al_(2)Cl_(6)` decomposes in the gas phase is :

Options

A. `sp^(2) to sp^(3)`
B. `sp to sp^(2)`
C. `sp to sp^(3)`
D. `sp^(3) to sp^(2)`

Answer

To determine the change in hybridization of aluminum when \( \text{Al}_2\text{Cl}_6 \) decomposes in the gas phase, we can follow these steps:

### Step 1: Understand the structure of \( \text{Al}_2\text{Cl}_6 \)
- \( \text{Al}_2\text{Cl}_6 \) is a dimer of aluminum chloride. Each aluminum atom in the dimer is surrounded by 6 chlorine atoms.

### Step 2: Determine the hybridization of aluminum in \( \text{Al}_2\text{Cl}_6 \)
- In \( \text{Al}_2\text{Cl}_6 \), each aluminum atom forms bonds with 4 chlorine atoms (due to dimerization) and has 0 lone pairs.
- The total number of bonding pairs (BP) is 4 and the number of lone pairs (LP) is 0.
- Hybridization can be determined using the formula:
\[ \text{Hybridization} = \text{Number of BP} + \text{Number of LP} \]
Therefore, for \( \text{Al}_2\text{Cl}_6 \):
\[ \text{Hybridization} = 4 + 0 = 4 \quad \Rightarrow \quad \text{SP}^3 \]

### Step 3: Understand the decomposition of \( \text{Al}_2\text{Cl}_6 \)
- Upon heating, \( \text{Al}_2\text{Cl}_6 \) decomposes into 2 moles of \( \text{AlCl}_3 \):
\[ \text{Al}_2\text{Cl}_6 \xrightarrow{\text{heat}} 2 \text{AlCl}_3 \]

### Step 4: Determine the hybridization of aluminum in \( \text{AlCl}_3 \)
- In \( \text{AlCl}_3 \), each aluminum atom is bonded to 3 chlorine atoms.
- Here, the number of bonding pairs (BP) is 3 and the number of lone pairs (LP) is 0.
- Again, using the hybridization formula:
\[ \text{Hybridization} = 3 + 0 = 3 \quad \Rightarrow \quad \text{SP}^2 \]

### Step 5: Conclusion on the change in hybridization
- The hybridization changes from \( \text{SP}^3 \) in \( \text{Al}_2\text{Cl}_6 \) to \( \text{SP}^2 \) in \( \text{AlCl}_3 \).
- Therefore, the change in hybridization of aluminum when \( \text{Al}_2\text{Cl}_6 \) decomposes is from \( \text{SP}^3 \) to \( \text{SP}^2 \).

### Final Answer
The change in hybridization of aluminum when \( \text{Al}_2\text{Cl}_6 \) decomposes in the gas phase is from \( \text{SP}^3 \) to \( \text{SP}^2 \).

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