Assertion: Complex ion `[Co(NH_(3))_(6)]^(2+)` is readily oxidized to `[Co(NH_(3))_(6)]^(3+)`
Reason: Unpaired electron in complex ion `[Co(NH_(3))_(6)]^(2+)` is present in 4p orbital.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true but reason is not the correct explanation of assertion

Answer

To analyze the given assertion and reason, we will break down the problem step by step.

### Step 1: Determine the oxidation state of cobalt in `[Co(NH₃)₆]²⁺`
- The complex ion `[Co(NH₃)₆]²⁺` consists of cobalt (Co) and six ammonia (NH₃) ligands.
- Since NH₃ is a neutral ligand (charge = 0), the oxidation state of cobalt can be determined as follows:
\[ \text{Oxidation state of Co} + 6 \times 0 = +2 \implies \text{Oxidation state of Co} = +2 \]

### Step 2: Determine the electron configuration of cobalt in the +2 oxidation state
- Cobalt has an atomic number of 27. The electron configuration of neutral cobalt is:
\[ [Ar] 3d^7 4s^2 \]
- For Co²⁺, we remove two electrons from the 4s orbital first:
\[ \text{Electron configuration of Co}^{2+} = [Ar] 3d^7 \]

### Step 3: Analyze the orbital filling of `[Co(NH₃)₆]²⁺`
- The 3d orbitals will be filled according to Hund's rule and the Pauli exclusion principle.
- With 7 electrons in the 3d orbitals, the distribution will be:
- 3d: ↑↓ ↑↓ ↑ ↑ ↑ (1 unpaired electron remains)

### Step 4: Determine the oxidation state of cobalt in `[Co(NH₃)₆]³⁺`
- For the complex ion `[Co(NH₃)₆]³⁺`, the oxidation state of cobalt is +3:
\[ \text{Oxidation state of Co} + 6 \times 0 = +3 \implies \text{Oxidation state of Co} = +3 \]

### Step 5: Determine the electron configuration of cobalt in the +3 oxidation state
- For Co³⁺, we remove one more electron from the 3d orbital:
\[ \text{Electron configuration of Co}^{3+} = [Ar] 3d^6 \]

### Step 6: Analyze the orbital filling of `[Co(NH₃)₆]³⁺`
- The 3d orbitals will now have 6 electrons:
- 3d: ↑↓ ↑↓ ↑ ↑ (all electrons are paired)

### Step 7: Conclusion about the assertion
- The assertion states that `[Co(NH₃)₆]²⁺` is readily oxidized to `[Co(NH₃)₆]³⁺`. This is correct because the +3 oxidation state is more stable due to all electrons being paired.

### Step 8: Conclusion about the reason
- The reason states that the unpaired electron in `[Co(NH₃)₆]²⁺` is in the 4p orbital. This is incorrect as the unpaired electron is in the 3d orbital.

### Final Conclusion
- The assertion is correct, but the reason is incorrect.