The number of `90^@` angles (approximately) in `PHF_4` is………..

Answer

To determine the number of 90° angles in the molecule PHF₄, we can follow these steps:

### Step 1: Identify the central atom and its hybridization
- The central atom in PHF₄ is phosphorus (P).
- Phosphorus has 5 valence electrons and forms 4 bonds with fluorine (F) and has one lone pair of electrons.

### Step 2: Determine the hybridization of the central atom
- The hybridization can be determined by counting the number of bonds and lone pairs around the central atom.
- In PHF₄, there are 4 bonds (to F) and 1 lone pair.
- Therefore, the total number of regions of electron density is 5 (4 bonds + 1 lone pair).
- This corresponds to sp³d hybridization.

### Step 3: Understand the geometry of the molecule
- The geometry associated with sp³d hybridization is trigonal bipyramidal.
- In a trigonal bipyramidal structure, there are two types of positions: axial and equatorial.

### Step 4: Identify the angles in the structure
- In a trigonal bipyramidal geometry:
- The axial positions are 180° apart and have 90° angles with the equatorial positions.
- The equatorial positions are 120° apart.

### Step 5: Count the number of 90° angles
- In the case of PHF₄, the fluorine atoms (being more electronegative) occupy the axial positions, while the lone pair occupies one of the equatorial positions.
- This configuration results in 4 F atoms forming 90° angles with the lone pair and the other F atoms in the equatorial plane.
- Therefore, there are a total of 6 90° angles in the structure.

### Conclusion
The number of 90° angles in PHF₄ is approximately **6**.

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