Which of the following set is pair of isoster species.

Answer

To determine which of the following sets is a pair of isosteric species, we need to understand the definition of isosteres. Isosteres are molecules or ions that have similar shapes and often exhibit similar electronic properties, despite having different chemical compositions.

Let's analyze the options provided:

1. **Identify the pairs**: We need to look at the pairs given in the question. For this solution, we will focus on the pair CO2 and N2O.

2. **Check for similar shapes**:
- CO2 (carbon dioxide) is a linear molecule with the structure O=C=O.
- N2O (nitrous oxide) can be represented as N=N=O or N-O-N, depending on the resonance structures, but it also has a linear arrangement.

3. **Check for similar electronic properties**:
- Both CO2 and N2O have similar electron configurations and bonding characteristics. CO2 has a double bond between carbon and each oxygen, while N2O has a nitrogen-oxygen bond and a nitrogen-nitrogen bond, which can also exhibit similar electronic characteristics.

4. **Conclusion**: Since both CO2 and N2O have a similar shape and comparable electronic properties, they can be classified as isosteres.

Thus, the answer is that CO2 and N2O form a set of isosteric species.

### Step-by-step Solution Summary:
1. Define isosteres: Molecules or ions with similar shapes and electronic properties.
2. Analyze the first pair: CO2 is linear, and N2O can also be linear.
3. Compare electronic properties: Both have similar bonding characteristics.
4. Conclude that CO2 and N2O are isosteres.