Which of the following are true ?.

Options

A. `PH_(5)` and `BiCI_(5)` do not exist
B. There are two `ppi-dpi` bond is `SO_(3)`
C. `SeF_(4)` and `CH_(4)` are tetrahedral ion
D. `I_(3)^(Θ)` is a linear molecule with `sp^(3)` d hybridisation

Explanation

To determine which statements are true regarding the compounds mentioned, we will analyze each statement step by step.

### Step 1: Analyze pH5 and BiCl5
- **Statement**: pH5 and BiCl5 do not exist.
- **Explanation**: Phosphorus (P) is more electronegative than hydrogen (H), which means that H cannot exert enough charge to allow phosphorus to achieve a valency of 5. Therefore, pH5 does not exist. Similarly, BiCl5 is also not stable due to similar reasons.
- **Conclusion**: This statement is **true**.

### Step 2: Analyze SO3 and p pi d pi bonds
- **Statement**: There are two p pi d pi bonds in SO3.
- **Explanation**: Sulfur (S) is a third-period element and has access to d orbitals. In SO3, sulfur can form p pi d pi bonds with the oxygen atoms. The presence of these bonds is due to the ability of sulfur to utilize its d orbitals in bonding.
- **Conclusion**: This statement is **true**.

### Step 3: Analyze SeF4 and CH4 structures
- **Statement**: SeF4 and CH4 are tetrahedral.
- **Explanation**: CH4 (methane) has a tetrahedral structure due to its four equivalent C-H bonds. However, SeF4 (selenium tetrafluoride) has a seesaw shape, which is not tetrahedral. Therefore, while CH4 is tetrahedral, SeF4 is not.
- **Conclusion**: This statement is **false**.

### Step 4: Analyze I3- structure and hybridization
- **Statement**: I3- is a linear molecule with sp3 hybridization.
- **Explanation**: The I3- ion has a linear structure due to the arrangement of three iodine atoms, but it does not have sp3 hybridization. The correct hybridization for I3- is sp3d, as it involves the presence of lone pairs and a linear arrangement.
- **Conclusion**: This statement is **false**.

### Final Conclusion:
The true statements are:
1. pH5 and BiCl5 do not exist. (True)
2. There are two p pi d pi bonds in SO3. (True)
3. SeF4 and CH4 are tetrahedral. (False)
4. I3- is a linear molecule with sp3 hybridization. (False)

Thus, the correct options are **A and B**.

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