Which among the following pairs of molecules have zero dipole moment ? .

Options

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

Explanation

To determine which pairs of molecules have zero dipole moment, we need to analyze the molecular structures and their symmetry. Here’s a step-by-step solution:

### Step 1: Analyze the first pair - SiF4 and CO2
1. **SiF4 Structure**: Silicon tetrafluoride (SiF4) has a tetrahedral geometry with silicon at the center and four fluorine atoms at the corners.
2. **Symmetry**: The molecule is symmetrical, and the dipole moments of the Si-F bonds cancel each other out. Therefore, SiF4 has a net dipole moment of zero.
3. **CO2 Structure**: Carbon dioxide (CO2) has a linear structure with carbon in the center and two oxygen atoms on either side.
4. **Symmetry**: The dipole moments of the C=O bonds also cancel out due to the linear arrangement, resulting in a net dipole moment of zero.

**Conclusion for Pair A**: Both SiF4 and CO2 have zero dipole moments.

### Step 2: Analyze the second pair - SiF4 and NO2
1. **SiF4**: As discussed, SiF4 has a net dipole moment of zero.
2. **NO2 Structure**: Nitrogen dioxide (NO2) has a bent structure due to the presence of a lone electron on nitrogen.
3. **Symmetry**: The bent shape leads to an unequal distribution of charge, resulting in a net dipole moment that is not zero.

**Conclusion for Pair B**: SiF4 has zero dipole moment, but NO2 does not. Thus, this pair does not have zero dipole moment.

### Step 3: Analyze the third pair - CO2 and O2
1. **CO2**: As previously established, CO2 has a net dipole moment of zero.
2. **O2 Structure**: Oxygen (O2) is a diatomic molecule with two identical oxygen atoms.
3. **Symmetry**: Since both atoms are the same, there is no difference in electronegativity, leading to a net dipole moment of zero.

**Conclusion for Pair C**: Both CO2 and O2 have zero dipole moments.

### Step 4: Analyze the fourth pair - NO2 and O3
1. **NO2**: As established, NO2 has a net dipole moment that is not zero.
2. **O3 Structure**: Ozone (O3) has a bent structure as well, which leads to an uneven distribution of charge.
3. **Symmetry**: The bent shape of ozone also results in a net dipole moment that is not zero.

**Conclusion for Pair D**: NO2 does not have zero dipole moment, and O3 also does not. Thus, this pair does not have zero dipole moment.

### Final Answer:
The pairs of molecules that have zero dipole moment are:
- **A: SiF4 and CO2**
- **C: CO2 and O2**