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 each option step by step.

### Step 1: Analyze BEF2
- **Valence Electrons**: Beryllium (Be) has 2 valence electrons, and each fluorine (F) has 7 valence electrons. Therefore, the total valence electrons = 2 + (2 × 7) = 16.
- **Bonding**: There are 2 sigma bonds formed between Be and the two F atoms.
- **Hybridization**: The hybridization of Be in BEF2 is sp, which gives it a linear geometry.
- **Dipole Moment**: In a linear molecule with two identical polar bonds (Be-F), the dipoles cancel each other out, resulting in a net dipole moment of 0.

### Step 2: Analyze BF3
- **Valence Electrons**: Boron (B) has 3 valence electrons, and each fluorine (F) has 7 valence electrons. Therefore, the total valence electrons = 3 + (3 × 7) = 24.
- **Bonding**: There are 3 sigma bonds between B and the three F atoms.
- **Hybridization**: The hybridization of B in BF3 is sp2, which gives it a trigonal planar geometry.
- **Dipole Moment**: Similar to BEF2, the dipoles from the three B-F bonds cancel each other out due to symmetry, resulting in a net dipole moment of 0.

### Step 3: Analyze H2O
- **Valence Electrons**: Oxygen (O) has 6 valence electrons, and each hydrogen (H) has 1 valence electron. Therefore, the total valence electrons = 6 + (2 × 1) = 8.
- **Bonding**: There are 2 sigma bonds between O and the two H atoms, and there are 2 lone pairs on O.
- **Hybridization**: The hybridization of O in H2O is sp3, which gives it a tetrahedral electron geometry but a bent molecular shape due to the lone pairs.
- **Dipole Moment**: The molecule is polar because the oxygen atom is more electronegative than hydrogen, creating a dipole moment directed towards the oxygen. Thus, H2O has a significant dipole moment.

### Step 4: Analyze the Fourth Option
- Since the fourth option is not specified in the question, we can assume it is another molecule with a dipole moment of 0 or less than H2O.

### Conclusion
Among the analyzed compounds, H2O has the highest dipole moment due to its bent shape and the electronegativity difference between O and H.

### Final Answer
The compound with the highest dipole moment is **H2O**.

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