Which of the following statement is correct ?

Options

A. Boron and aluminium halides behave as Lewis acids
B. Al forms `[Al F_(6)]^(3-)` ion but B does not form `[BF_(6)]^(3-)` ion
C. The `p pi - p pi` back bonding occurs in the halides of boron and not in those of aluminium
D. All of these

Answer

To determine which of the statements about boron and aluminum halides is correct, we will analyze each statement step by step.

### Step 1: Understanding Lewis Acids
**Statement 1:** "Boron and Aluminum Halides behave as Lewis Acids."
- **Explanation:** Lewis acids are defined as electron pair acceptors. Boron (atomic number 5) has an electronic configuration of 1s² 2s² 2p¹, meaning it has three valence electrons. Aluminum (atomic number 13) has an electronic configuration of 1s² 2s² 2p⁶ 3s² 3p¹, with three valence electrons as well. Both boron and aluminum can accept electron pairs from other species to complete their octets, thus behaving as Lewis acids. Therefore, this statement is correct.

### Step 2: Formation of Complex Ions
**Statement 2:** "Aluminum forms AlF₆³⁻ but Boron does not form BF₆³⁻."
- **Explanation:** Aluminum can expand its octet due to the presence of vacant d-orbitals, allowing it to form the complex ion AlF₆³⁻. In contrast, boron does not have vacant d-orbitals and cannot accommodate more than 8 electrons in its valence shell. Therefore, it cannot form BF₆³⁻. This statement is also correct.

### Step 3: Back Bonding in Halides
**Statement 3:** "The p-π-p-π back bonding occurs in the halides of boron and not in those of aluminum."
- **Explanation:** In boron halides, the small size of boron allows for effective overlap with the p-orbitals of halogens, enabling p-π-p-π back bonding. However, in aluminum halides, the larger size of aluminum means that there is less effective overlap, and thus, back bonding does not occur. This statement is correct as well.

### Step 4: Conclusion
**Statement 4:** "All of these 3 options are correct."
- **Explanation:** Since statements 1, 2, and 3 have been verified as correct, statement 4 is also correct.

### Final Answer
The correct answer is **Option 4: All of these statements are correct.**

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