Amongst the following the total number of species which does/do not exist is :
`SF_6,BF_6^(3-), SF_4, OF_4, AIF_6^(3-),PH_5, PCl_5, NCl_5, SCl_6`

Explanation

To determine the total number of species that do not exist from the given list, we will analyze each species one by one based on their electronic configurations and bonding capabilities.

### Step-by-Step Solution:

1. **SF₆ (Sulfur Hexafluoride)**:
- SF₆ exists. Sulfur can accommodate six fluorine atoms due to its ability to expand its octet, making it stable.

2. **BF₆³⁻ (Boron Hexafluoride anion)**:
- BF₆³⁻ does not exist. Boron does not have vacant d orbitals to expand its coordination number beyond four, thus it cannot accommodate six fluorine atoms.

3. **SF₄ (Sulfur Tetrafluoride)**:
- SF₄ exists. Sulfur can form four bonds with fluorine and has a lone pair, making it stable.

4. **OF₄ (Oxygen Tetrafluoride)**:
- OF₄ does not exist. Oxygen cannot expand its octet beyond four bonds as it lacks vacant d orbitals.

5. **AlF₆³⁻ (Aluminum Hexafluoride anion)**:
- AlF₆³⁻ exists. Aluminum has vacant d orbitals and can accommodate six fluorine atoms, forming a stable octahedral complex.

6. **PH₅ (Phosphorus Pentahydride)**:
- PH₅ does not exist. The energy difference between the p and d orbitals in phosphorus is too large for it to form five bonds with hydrogen.

7. **PCl₅ (Phosphorus Pentachloride)**:
- PCl₅ exists. Phosphorus can expand its octet and form five bonds with chlorine due to the availability of vacant d orbitals.

8. **NCl₅ (Nitrogen Pentachloride)**:
- NCl₅ does not exist. Nitrogen cannot expand its coordination number beyond four due to the absence of vacant d orbitals.

9. **SCl₆ (Sulfur Hexachloride)**:
- SCl₆ does not exist. Similar to OF₄, sulfur cannot accommodate six larger chlorine atoms due to steric hindrance and lack of available orbitals.

### Summary of Existence:
- **Species that exist**: SF₆, SF₄, AlF₆³⁻, PCl₅
- **Species that do not exist**: BF₆³⁻, OF₄, PH₅, NCl₅, SCl₆

### Total Number of Species that Do Not Exist:
There are **5 species** that do not exist.

### Final Answer:
The total number of species that do not exist is **5**.

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