Question

Given below are two statements. Statement I: First ionisation enthalpy of Cr is greater than that of Mn. Statement II: Second and third ionisation enthalpies of Cr are less than that of Mn. In the light of above statements, choose the correct option.

• A. Both statement I and statement II are correct
• B. Both statement I and statement II are incorrect
• C. Statement I is correct but statement II is incorrect
• D. Statement I is incorrect but statement II is correct

Hint:

Ionisation enthalpies depend on the stability of the electron configuration, and Cr has a more stable configuration than Mn after the first ionisation.

Answer 1

The Correct Option is C

Step 1: Analyze statement I.
The first ionisation enthalpy of Cr is indeed greater than that of Mn. This is due to the fact that Cr has a more stable electron configuration (3d\(^5\)4s\(^1\)) compared to Mn, which makes it harder to remove an electron. Step 2: Analyze statement II.
However, the second and third ionisation enthalpies of Cr are higher than those of Mn. This is because, after the removal of the first electron, Cr becomes a stable ion with a half-filled d-subshell, making it harder to remove additional electrons compared to Mn. Step 3: Conclusion.
Thus, Statement I is correct, but Statement II is incorrect. Final Answer: \[ \boxed{\text{Statement I is correct but statement II is incorrect}}. \]