Question

Given below are two statements:
Statement I: The first ionization enthalpy of Cr is lower than that of Mn.
Statement II: The second and third ionization enthalpies of Cr are higher than those of Mn.
In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Statement I is true but Statement II is false
• C. Statement I is false but Statement II is true
• D. Both Statement I and Statement II are false

Hint:

Exceptional stability of half-filled and fully-filled subshells strongly influences ionization enthalpies of transition elements.

Answer 1

The Correct Option is A

Step 1: Analyze Statement I.
Electronic configurations: \[ \text{Cr: } [Ar]\,3d^5\,4s^1, \quad \text{Mn: } [Ar]\,3d^5\,4s^2 \] In chromium, removal of one electron leads to the particularly stable half-filled \(3d^5\) configuration. Hence, the first ionization enthalpy of Cr is lower than that of Mn. Therefore, Statement I is true.

Step 2: Analyze Statement II.
After the first ionization, chromium forms \( \text{Cr}^+ \) with configuration \(3d^5\), which is highly stable. Removing the second and third electrons from this stable half-filled \(3d^5\) configuration requires more energy. In contrast, manganese does not gain such exceptional stability after the first ionization. Therefore, the second and third ionization enthalpies of Cr are higher than those of Mn. Hence, Statement II is also true.

Step 3: Final conclusion.
Both Statement I and Statement II are true.

Final Answer: \[ \boxed{\text{Both Statement I and Statement II are true}} \]