The molecule which has zero dipole moment is

Options

A. `CH_(2)CI_(2)`
B. `BF_(3)`
C. `NF_(3)`
D. `CIO_(3)`

Explanation

To determine which molecule has a zero dipole moment, we will analyze the dipole moments of the given molecules step by step.

### Step 1: Understanding Dipole Moment
Dipole moment is a vector quantity that arises from the separation of positive and negative charges in a molecule. A molecule has a zero dipole moment if the individual dipole moments cancel each other out due to symmetry.

### Step 2: Analyze CH2Cl2
- **Structure**: CH2Cl2 has a central carbon atom bonded to two hydrogen atoms and two chlorine atoms.
- **Electronegativity**: Chlorine is more electronegative than carbon, which means it attracts electron density towards itself.
- **Dipole Moment**: The dipole moments from the two Cl atoms will not cancel out due to the asymmetrical arrangement of hydrogen and chlorine. Therefore, CH2Cl2 has a net dipole moment that is not zero.

### Step 3: Analyze BF3
- **Structure**: BF3 has a central boron atom bonded to three fluorine atoms arranged in a trigonal planar geometry.
- **Electronegativity**: Each fluorine atom is highly electronegative and attracts electron density towards itself.
- **Dipole Moment**: The symmetry of the trigonal planar structure means that the dipole moments from the three fluorine atoms cancel each other out. Therefore, BF3 has a zero dipole moment.

### Step 4: Analyze NF3
- **Structure**: NF3 has a central nitrogen atom bonded to three fluorine atoms, with one lone pair on nitrogen.
- **Electronegativity**: The fluorine atoms attract electron density towards themselves, while the lone pair on nitrogen also attracts electron density.
- **Dipole Moment**: The presence of the lone pair creates an asymmetry in the molecule, leading to a net dipole moment. Therefore, NF3 does not have a zero dipole moment.

### Step 5: Analyze ClO3^-
- **Structure**: ClO3^- (chlorate ion) has a central chlorine atom bonded to three oxygen atoms and has a negative charge.
- **Electronegativity**: The oxygen atoms are more electronegative than chlorine and will attract electron density towards themselves.
- **Dipole Moment**: The presence of a lone pair on chlorine and the arrangement of the oxygen atoms creates an asymmetrical distribution of charge. Therefore, ClO3^- does not have a zero dipole moment.

### Conclusion
After analyzing all the given molecules, we find that the only molecule with a zero dipole moment is **BF3**.