Assertion (A) : Highest oxidation state of Mn is +7 in first series of transition elements.
Reason (R) : Transition metals exhibit variable oxidation states.
Reason (R) : Transition metals exhibit variable oxidation states.
Show Hint
Mn shows the maximum number of oxidation states (+2 to +7) in the first series.
Variable oxidation state is a general property; specific values depend on the configuration.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
The Correct Option is B
Solution and Explanation
• Transition elements show variable oxidation states because of the small energy difference between \( (n-1)d \) and \( ns \) orbitals.
• The maximum oxidation state for a transition metal is often determined by the total number of \( ns \) and \( (n-1)d \) electrons.
Step 1: Analyze the Assertion
Manganese \( (\text{Mn}) \) has the electronic configuration \( [ \text{Ar} ] 3d^5 4s^2 \).
It can lose or share all 7 valence electrons (5 from \( 3d \) and 2 from \( 4s \)).
This results in a maximum oxidation state of +7, which is indeed the highest in the \( 3d \) transition series.
Assertion is True.
Step 2: Analyze the Reason
Transition metals exhibit variable oxidation states because electrons from both \( ns \) and \( (n-1)d \) subshells can participate in bonding.
Reason is True.
Step 3: Check for logical connection
While the reason is a general characteristic of transition metals, it does not specifically explain *why* Mn reaches +7.
The specific explanation for Mn being +7 is that it has the maximum number of unpaired electrons in the \( 3d \) subshell along with \( 4s \) electrons available for bonding.
The final answer is (B).
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