Which of the following pairs are isosters ?

Options

A. `CO_(2)` and `N_(2)O`
B. `CaO` and KF
C. `OF_(2)` and HCIO
D. All of these

Explanation

To determine which pairs are isosters, we need to follow these steps:

### Step 1: Understand the Definition of Isosters
Isosters are molecules or ions that have the same number of atoms and the same number of total electrons, but may differ in the types of atoms present.

### Step 2: Analyze Each Option
We will analyze each option given in the question to see if they meet the criteria for being isosters.

#### Option A: CO₂ and N₂O
1. **Count the Atoms**:
- CO₂: 1 Carbon (C) + 2 Oxygen (O) = 3 atoms
- N₂O: 2 Nitrogen (N) + 1 Oxygen (O) = 3 atoms
- Both have 3 atoms.

2. **Count the Electrons**:
- CO₂: Carbon has 6 electrons + 2 Oxygen (8 each) = 6 + 16 = 22 electrons.
- N₂O: 2 Nitrogen (7 each) + 1 Oxygen (8) = 14 + 8 = 22 electrons.
- Both have 22 electrons.

**Conclusion**: CO₂ and N₂O are isosters.

#### Option B: CaO and KF
1. **Count the Atoms**:
- CaO: 1 Calcium (Ca) + 1 Oxygen (O) = 2 atoms
- KF: 1 Potassium (K) + 1 Fluorine (F) = 2 atoms
- Both have 2 atoms.

2. **Count the Electrons**:
- CaO: Calcium has 20 electrons + Oxygen has 8 = 20 + 8 = 28 electrons.
- KF: Potassium has 19 electrons + Fluorine has 9 = 19 + 9 = 28 electrons.
- Both have 28 electrons.

**Conclusion**: CaO and KF are isosters.

#### Option C: O₂ and HClO
1. **Count the Atoms**:
- O₂: 2 Oxygen (O) = 2 atoms
- HClO: 1 Hydrogen (H) + 1 Chlorine (Cl) + 1 Oxygen (O) = 3 atoms
- They do not have the same number of atoms.

**Conclusion**: O₂ and HClO are not isosters.

#### Option D: H₂O and HCl
1. **Count the Atoms**:
- H₂O: 2 Hydrogen (H) + 1 Oxygen (O) = 3 atoms
- HCl: 1 Hydrogen (H) + 1 Chlorine (Cl) = 2 atoms
- They do not have the same number of atoms.

**Conclusion**: H₂O and HCl are not isosters.

### Final Conclusion
The pairs that are isosters are:
- **Option A: CO₂ and N₂O**
- **Option B: CaO and KF**