Which of the following will have the highest dipole moment ?

Options

A. `BeF_(2)`
B. `BF_(3)`
C. `H_(2)O`
D. All have zero dipole moment

Answer

To determine which of the given compounds has the highest dipole moment, we will analyze the molecular geometry and electronegativity of the atoms involved in each compound. The compounds we will consider are BEF2, BF3, and H2O.

### Step 1: Analyze BEF2
- **Molecular Structure**: BEF2 has a linear structure due to sp hybridization.
- **Lone Pairs and Bond Pairs**: It has 0 lone pairs and 2 bond pairs.
- **Dipole Moment**: The dipole moments of the two B-F bonds will cancel each other out because they are in opposite directions. Therefore, the net dipole moment (μ) for BEF2 is 0.

### Step 2: Analyze BF3
- **Molecular Structure**: BF3 has a trigonal planar structure due to sp² hybridization.
- **Lone Pairs and Bond Pairs**: It has 0 lone pairs and 3 bond pairs.
- **Dipole Moment**: The dipole moments of the three B-F bonds will also cancel out because they are symmetrically arranged at 120° angles. Thus, the net dipole moment (μ) for BF3 is 0.

### Step 3: Analyze H2O
- **Molecular Structure**: H2O has a bent shape due to sp³ hybridization.
- **Lone Pairs and Bond Pairs**: It has 2 lone pairs and 2 bond pairs.
- **Dipole Moment**: The dipole moments of the two O-H bonds do not cancel out due to the bent shape of the molecule. The net dipole moment (μ) for H2O is not equal to 0, and it is significant because of the difference in electronegativity between oxygen and hydrogen.

### Conclusion
After analyzing all three compounds:
- BEF2: μ = 0
- BF3: μ = 0
- H2O: μ > 0

Thus, the compound with the highest dipole moment is **H2O**.