Total number of F-l-F bond angles which are `90^(@)` present in `lF_(7)` is

Options

A. zero
B. Two
C. Five
D. Ten

Answer

To solve the question regarding the total number of F-I-F bond angles that are 90 degrees in IF7, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Central Atom and its Valence Electrons**:
- The central atom in IF7 is iodine (I). Iodine has an atomic number of 53.
- The electronic configuration of iodine is [Kr] 4d10 5s2 5p5, which indicates that iodine has 7 valence electrons.

2. **Determine the Surrounding Atoms and their Valence Electrons**:
- The surrounding atom is fluorine (F). Fluorine has an atomic number of 9.
- The electronic configuration of fluorine is 1s2 2s2 2p5, which means fluorine has 7 valence electrons and needs one more to complete its octet.

3. **Calculate the Steric Number**:
- The steric number is calculated using the formula:
\[ \text{Steric Number} = \frac{1}{2} \left( \text{Total Valence Electrons of Central Atom} + \text{Number of Monovalent Atoms} - \text{Cations} + \text{Anions} \right) \]
- For IF7:
- Total valence electrons from iodine = 7
- Number of monovalent fluorine atoms = 7
- No cations or anions.
- Therefore:
\[ \text{Steric Number} = \frac{1}{2} (7 + 7) = 7 \]

4. **Determine the Geometry and Hybridization**:
- According to VSEPR theory, a steric number of 7 corresponds to a pentagonal bipyramidal geometry.
- The hybridization for this geometry is \( sp^3d^3 \).

5. **Visualize the Geometry**:
- In a pentagonal bipyramidal structure, there are five fluorine atoms in a plane (equatorial positions) and two fluorine atoms above and below this plane (axial positions).

6. **Identify the Bond Angles**:
- The bond angles between the axial fluorine atoms (above and below the plane) and the equatorial fluorine atoms (in the plane) are 90 degrees.
- There are 5 equatorial fluorine atoms, each forming a 90-degree angle with the two axial fluorine atoms.

7. **Count the Total 90-Degree Angles**:
- Each of the 5 equatorial fluorine atoms forms a 90-degree angle with both of the axial fluorine atoms.
- Thus, the total number of 90-degree angles is:
\[ 5 \text{ (from above)} + 5 \text{ (from below)} = 10 \]

### Final Answer:
The total number of F-I-F bond angles that are 90 degrees in IF7 is **10**.