In which of the following compounds resonance does not occurs
(a) `H_2O` (b) `SiO_2` (c ) `SO_2` (d) `CO_2`

Options

A. a and d
B. a and b
C. c and d
D. b, c and d

Answer

To determine which of the following compounds does not exhibit resonance, we will analyze each option step by step.

### Step 1: Analyze `H2O` (Water)
- **Structure**: Water has the molecular formula `H2O`, where the oxygen atom is bonded to two hydrogen atoms. The oxygen has two lone pairs of electrons.
- **Resonance**: In water, the bonds between hydrogen and oxygen are single bonds. There are no double bonds or conjugated systems present that would allow for the delocalization of electrons. Therefore, water does not have any resonance structures.

### Step 2: Analyze `SiO2` (Silicon Dioxide)
- **Structure**: Silicon dioxide is a network solid, commonly found in nature as quartz or sand. It consists of a three-dimensional lattice structure where silicon atoms are bonded to oxygen atoms.
- **Resonance**: Due to its extensive three-dimensional network structure, SiO2 does not have distinct resonance structures. The bonding in SiO2 is covalent and does not involve delocalized electrons in the same way as molecules with resonance do. Thus, SiO2 does not exhibit resonance.

### Step 3: Analyze `SO2` (Sulfur Dioxide)
- **Structure**: Sulfur dioxide has the molecular formula `SO2`, where sulfur is bonded to two oxygen atoms. Sulfur has one lone pair of electrons.
- **Resonance**: In SO2, there are double bonds between sulfur and oxygen, and the lone pair on sulfur can participate in resonance. The structure can be represented with different resonance forms by shifting the double bond between sulfur and the two oxygen atoms. Therefore, SO2 does exhibit resonance.

### Step 4: Analyze `CO2` (Carbon Dioxide)
- **Structure**: Carbon dioxide has the molecular formula `CO2`, where carbon is double bonded to two oxygen atoms.
- **Resonance**: Similar to SO2, CO2 can also be represented with resonance structures. The double bonds can be shifted, allowing for the delocalization of electrons. Thus, CO2 does exhibit resonance.

### Conclusion
After analyzing all the compounds, we find that:
- `H2O` (Water) does not exhibit resonance.
- `SiO2` (Silicon Dioxide) does not exhibit resonance.
- `SO2` (Sulfur Dioxide) exhibits resonance.
- `CO2` (Carbon Dioxide) exhibits resonance.

### Final Answer
The compounds in which resonance does not occur are:
- (a) `H2O`
- (b) `SiO2`

Thus, the correct options are (a) and (b).

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