To determine which species has a bond angle of exactly 109°28', we will analyze the given options systematically.
### Step 1: Identify the species and their central atoms
We need to analyze the bond angles around the central atom for each species provided in the options. The species mentioned in the video are SF4 and NH3.
### Step 2: Analyze SF4 (Sulfur Tetrafluoride)
1. **Valence Electrons**: Sulfur (S) has 6 valence electrons, and each fluorine (F) has 1 valence electron. Therefore, the total number of valence electrons is:
\[
6 + 4 \times 1 = 10 \text{ valence electrons}
\]
2. **Bonding**: Sulfur forms bonds with 4 fluorine atoms, using 4 of its valence electrons.
3. **Lone Pair**: After forming 4 bonds, there are 2 electrons left, which form 1 lone pair.
4. **Steric Number**: The steric number (number of bonded atoms + lone pairs) is:
\[
4 \text{ (bond pairs)} + 1 \text{ (lone pair)} = 5
\]
5. **Hybridization**: The hybridization is \( sp^3d \).
6. **Geometry**: The geometry is trigonal bipyramidal, but the shape is seesaw due to the lone pair.
7. **Bond Angles**: The bond angles are less than 120° and less than 90° due to lone pair repulsion. Therefore, the bond angle is not 109°28'.
### Step 3: Analyze NH3 (Ammonia)
1. **Valence Electrons**: Nitrogen (N) has 5 valence electrons, and each hydrogen (H) has 1 valence electron. Therefore, the total number of valence electrons is:
\[
5 + 3 \times 1 = 8 \text{ valence electrons}
\]
2. **Bonding**: Nitrogen forms bonds with 3 hydrogen atoms, using 3 of its valence electrons.
3. **Lone Pair**: After forming 3 bonds, there are 2 electrons left, which form 1 lone pair.
4. **Steric Number**: The steric number is:
\[
3 \text{ (bond pairs)} + 1 \text{ (lone pair)} = 4
\]
5. **Hybridization**: The hybridization is \( sp^3 \).
6. **Geometry**: The geometry is tetrahedral, but the shape is trigonal pyramidal due to the lone pair.
7. **Bond Angles**: The ideal bond angle for tetrahedral geometry is 109.5°, but due to the lone pair, the bond angle is approximately 107°. Therefore, the bond angle is not 109°28'.
### Step 4: Conclusion
Since neither SF4 nor NH3 has a bond angle of exactly 109°28', we need to check if there are other species provided in the options. However, based on the analysis of the two species discussed, neither meets the criteria.
### Final Answer
None of the species analyzed (SF4 and NH3) have a bond angle of exactly 109°28'.
---
