Which of the following halides cannot be hydrolysed? (I) `TeF_(6) (II) SF_(6) (III) NCl_(3) (IV) NF_3`
Choose the correct code.

Options

A. III and IV
B. I, II and III
C. I, II and IV
D. II and IV

Answer

To determine which of the given halides cannot be hydrolyzed, we will analyze each compound based on their molecular structure and the ability to interact with water molecules.

### Step-by-Step Solution:

1. **Understanding Hydrolysis**:
Hydrolysis involves the reaction of a compound with water, typically requiring the coordination of water molecules to the central atom of the compound. This often necessitates the presence of vacant orbitals to accommodate the lone pairs from water.

2. **Analyzing `TeF6`**:
- **Structure**: Tellurium hexafluoride (TeF6) has an octahedral geometry and can undergo hydrolysis because tellurium has vacant d-orbitals that can accept lone pairs from water.
- **Conclusion**: `TeF6` can be hydrolyzed.

3. **Analyzing `SF6`**:
- **Structure**: Sulfur hexafluoride (SF6) also has an octahedral geometry with sp³d² hybridization. However, it is highly stable and compact, with no dipole moment, which makes it difficult for water molecules to approach and react.
- **Conclusion**: `SF6` cannot be hydrolyzed.

4. **Analyzing `NCl3`**:
- **Structure**: Nitrogen trichloride (NCl3) has a trigonal pyramidal shape. Nitrogen has a lone pair and can interact with water molecules, allowing for hydrolysis.
- **Conclusion**: `NCl3` can be hydrolyzed.

5. **Analyzing `NF3`**:
- **Structure**: Nitrogen trifluoride (NF3) has a similar trigonal pyramidal shape as NCl3. However, nitrogen and fluorine do not have vacant d-orbitals to accept lone pairs from water, and the strong electronegativity of fluorine makes the molecule stable and unreactive towards hydrolysis.
- **Conclusion**: `NF3` cannot be hydrolyzed.

### Final Answer:
The halides that cannot be hydrolyzed are `SF6` and `NF3`. Therefore, the correct code is (II) and (IV).