The first compound of the noble gasees was made in 1962. Barlett and Lohman had previously used the highly oxidizing compound platium hexaflouride to oxidize dioxygen.
`O_(2)+PtF_(6) to O_(2)^(+)[PtF_(6)]^(-)`
The first ionization energy for `O_(2) to O_(2)` is `1165kJ*mol^(-1)`, which is almost as the value of `1170kJ*mol^(-1)` for `Xe to Xe^(+)`. It was predicated that xenon should react with `PtF_(6)`. Experimental showed that when deep of red `PtF_(6)` vapour was mixed with an equal volume of Xe the gases combined immediately at room temperature to produce a solid.
`Xe+PtF_(6) to Xe[PtF_(6)]`
Q. Which of the following species is not having perfect octahedron structure?

Options

A. `XeF_(6)`
B. `SiF_(6)^(2-)`
C. `PCl_(6)^(-)`
D. `XeO_(6)^(4-)`

Answer

To determine which of the following species does not have a perfect octahedral structure, we will analyze each option step by step.

### Step 1: Analyze the first option - XeF6
- **Valence Electrons**: Xenon (Xe) has 8 valence electrons. In XeF6, it forms 6 covalent bonds with fluorine (F).
- **Bond Pairs and Lone Pairs**:
- 6 bond pairs (one for each F).
- 2 electrons remain as a lone pair.
- **Steric Number**: The steric number is the sum of bond pairs and lone pairs. Here, it is 6 (bond pairs) + 1 (lone pair) = 7.
- **Hybridization**: With a steric number of 7, the hybridization is sp³d³.
- **Geometry**: The geometry is pentagonal bipyramidal, and the shape is a distorted octahedron.

**Conclusion for XeF6**: It does not have a perfect octahedral structure; it has a distorted octahedral structure.

### Step 2: Analyze the second option - SiF6²⁻
- **Valence Electrons**: Silicon (Si) has 4 valence electrons. With a 2- charge, it has 6 electrons total.
- **Bond Pairs**: Si forms 6 bonds with fluorine.
- **Lone Pairs**: There are no lone pairs.
- **Steric Number**: The steric number is 6 (6 bond pairs + 0 lone pairs).
- **Hybridization**: The hybridization is sp³d².
- **Geometry**: The geometry is octahedral.

**Conclusion for SiF6²⁻**: It has a perfect octahedral structure.

### Step 3: Analyze the third option - PCl6⁻
- **Valence Electrons**: Phosphorus (P) has 5 valence electrons. With a 1- charge, it has 6 electrons total.
- **Bond Pairs**: P forms 6 bonds with chlorine.
- **Lone Pairs**: There are no lone pairs.
- **Steric Number**: The steric number is 6 (6 bond pairs + 0 lone pairs).
- **Hybridization**: The hybridization is sp³d².
- **Geometry**: The geometry is octahedral.

**Conclusion for PCl6⁻**: It has a perfect octahedral structure.

### Step 4: Analyze the fourth option - XeO6²⁻
- **Valence Electrons**: Xenon (Xe) has 8 valence electrons. With a 2- charge, it has 10 electrons total.
- **Bond Pairs**: Xe forms 6 bonds with oxygen.
- **Lone Pairs**: There are no lone pairs.
- **Steric Number**: The steric number is 6 (6 bond pairs + 0 lone pairs).
- **Hybridization**: The hybridization is sp³d².
- **Geometry**: The geometry is octahedral.

**Conclusion for XeO6²⁻**: It has a perfect octahedral structure.

### Final Answer
The species that does not have a perfect octahedral structure is **XeF6**.

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