Which of the following pair of molecules will have permanent dipole moment?

Options

A. `NO_(2) and CO_(2)`
B. `NO_(2) and O_(3)`
C. `SiF_(4) and CO_(2)`
D. `SiF_(4) and NO_(2)`

Answer

To determine which pair of molecules has a permanent dipole moment, we need to analyze the molecular geometry and the electronegativity of the atoms involved in each molecule. Let's go through each molecule step by step.

### Step 1: Analyze NO2 (Nitrogen Dioxide)
1. **Structure**: NO2 has a bent molecular geometry due to the presence of a lone pair on nitrogen.
2. **Electronegativity**: Oxygen is more electronegative than nitrogen, leading to a dipole moment directed towards the oxygen atoms.
3. **Resultant Dipole Moment**: Since the molecule is bent, the dipole moments do not cancel out, resulting in a net dipole moment.

**Conclusion**: NO2 has a permanent dipole moment.

### Step 2: Analyze CO2 (Carbon Dioxide)
1. **Structure**: CO2 has a linear molecular geometry.
2. **Electronegativity**: Oxygen is more electronegative than carbon, creating dipole moments directed towards the oxygen atoms.
3. **Resultant Dipole Moment**: In a linear molecule, the dipole moments from both oxygen atoms cancel each other out.

**Conclusion**: CO2 does not have a permanent dipole moment.

### Step 3: Analyze SiF4 (Silicon Tetrafluoride)
1. **Structure**: SiF4 has a tetrahedral molecular geometry.
2. **Electronegativity**: Fluorine is more electronegative than silicon, leading to dipole moments directed towards the fluorine atoms.
3. **Resultant Dipole Moment**: The symmetrical arrangement of the four fluorine atoms causes the dipole moments to cancel out.

**Conclusion**: SiF4 does not have a permanent dipole moment.

### Step 4: Analyze O3 (Ozone)
1. **Structure**: Ozone has a bent structure, similar to NO2, with one double bond and one single bond between the oxygen atoms.
2. **Electronegativity**: The central oxygen atom has lone pairs, affecting the dipole moment direction.
3. **Resultant Dipole Moment**: The dipole moments do not cancel out due to the bent shape and the presence of lone pairs, leading to a net dipole moment.

**Conclusion**: O3 has a permanent dipole moment.

### Final Conclusion
The molecules that have a permanent dipole moment are **NO2** and **O3**.

### Answer
**The correct option is: NO2 and O3.**

---