The highly stable pair of ions are

Options

A. `Fe^(2+) and Fe^(3+)`
B. `Fe^(2+) and Mn^(3+)`
C. `Fe^(3+) and Mn^(2+)`
D. `Fe^(3+) and Fe^(4+)`

Answer

To determine the highly stable pair of ions, we need to analyze the electronic configurations of iron (Fe) and manganese (Mn) and their respective oxidation states. Here’s a step-by-step breakdown of the solution:

### Step 1: Determine the electronic configurations of Fe and Mn
- **Iron (Fe)** has an atomic number of 26. Its electronic configuration is:
\[ \text{Fe: } 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^6, 4s^2 \]
- **Manganese (Mn)** has an atomic number of 25. Its electronic configuration is:
\[ \text{Mn: } 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^5, 4s^2 \]

### Step 2: Identify the oxidation states and resulting configurations
- For **Fe**, when it loses 3 electrons (2 from the 4s orbital and 1 from the 3d orbital), we get:
\[ \text{Fe}^{3+}: 3d^5 \quad (\text{stable, half-filled}) \]
- For **Mn**, when it loses 2 electrons (2 from the 4s orbital), we get:
\[ \text{Mn}^{2+}: 3d^5 \quad (\text{stable, half-filled}) \]

### Step 3: Assess the stability of the ions
- The half-filled d-orbitals (3d^5) in both ions (Fe³⁺ and Mn²⁺) confer extra stability due to symmetry and exchange energy.
- Thus, both ions are highly stable due to their half-filled d-orbital configurations.

### Step 4: Identify the correct answer
- The highly stable pair of ions is:
\[ \text{Fe}^{3+} \text{ and } \text{Mn}^{2+} \]

### Conclusion
The highly stable pair of ions is **Fe³⁺ and Mn²⁺**.

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