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 of the given molecules have a permanent dipole moment, we need to analyze the molecular structure and electronegativity of the atoms involved in each molecule. The molecules in question are NO2, CO2, O3, and SiF4.

### Step-by-Step Solution:

1. **Analyze NO2 (Nitrogen Dioxide)**:
- The structure of NO2 is bent due to the presence of a lone pair on nitrogen.
- The electronegativity of oxygen is greater than that of nitrogen, leading to a dipole moment directed towards the oxygen atoms.
- 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.

2. **Analyze CO2 (Carbon Dioxide)**:
- The structure of CO2 is linear (O=C=O).
- The dipole moments from each C=O bond point in opposite directions.
- Since the molecule is symmetrical, the dipole moments cancel each other out.
- **Conclusion**: CO2 does not have a permanent dipole moment.

3. **Analyze O3 (Ozone)**:
- The structure of O3 is bent (with one single bond and one double bond between the oxygen atoms).
- The dipole moment is directed towards the more electronegative oxygen.
- Due to the bent shape, the dipole moments do not cancel out, resulting in a net dipole moment.
- **Conclusion**: O3 has a permanent dipole moment.

4. **Analyze SiF4 (Silicon Tetrafluoride)**:
- The structure of SiF4 is tetrahedral.
- The dipole moments from each Si-F bond point towards the fluorine atoms.
- Due to the symmetrical tetrahedral shape, these dipole moments cancel each other out.
- **Conclusion**: SiF4 does not have a permanent dipole moment.

### Final Answer:
The pairs of molecules that have a permanent dipole moment are **NO2 and O3**.