Back bonding in `BF_(3)` does not afect

Options

A. planarity, lewis acidic strength and bond angle
B. bond length, hybridisation and bond strength
C. bond angle, planarity, geometry
D. Lewis acidity, bond length, bond order (B-F)

Answer

To solve the question regarding the effects of back bonding in boron trifluoride (BF3), we will analyze the various factors mentioned in the options and determine which of them are not affected by back bonding.

### Step-by-Step Solution:

1. **Understanding Back Bonding**:
- Back bonding occurs when a filled p-orbital of a more electronegative atom (in this case, fluorine) donates a pair of electrons to an empty p-orbital of a less electronegative atom (boron). This process can affect various properties of the molecule.

2. **Analyzing the Structure of BF3**:
- Boron trifluoride has a trigonal planar structure due to sp² hybridization. The bond angle in BF3 is approximately 120 degrees.

3. **Identifying the Effects of Back Bonding**:
- **Planarity**: The trigonal planar shape of BF3 remains unchanged due to back bonding. Therefore, planarity is not affected.
- **Bond Angle**: The bond angle of 120 degrees also remains unchanged because back bonding does not alter the geometry of the molecule.
- **Lewis Acidity**: Back bonding can reduce the Lewis acidity of BF3 because it helps to stabilize the electron deficiency of boron by sharing electron density.

4. **Evaluating the Options**:
- **Option A**: Planarity, Lewis acidic strength, and bond angle. (Planarity and bond angle remain unchanged, but Lewis acidity decreases.)
- **Option B**: Bond length, hybridization, and bond strength. (Bond length decreases, hybridization remains unchanged, and bond strength increases.)
- **Option C**: Bond angle, planarity, and geometry. (All remain unchanged.)
- **Option D**: Lewis acidity, bond length, and bond order. (Lewis acidity decreases, bond length decreases, and bond order increases.)

5. **Conclusion**:
- The correct answer is **Option C**: bond angle, planarity, and geometry, as these factors are not affected by back bonding in BF3.