JEE Chemistry 2026 Question with Solution

Given: Two statements compare the ionization enthalpies of Cr and Mn.

Find: Which option correctly identifies the truth values of Statement I and Statement II.

Step 1: Analyze Statement I. Electronic configurations are

$$\text{Cr: } [Ar] \, 3d^5 \, 4s^1, \quad \text{Mn: } [Ar] \, 3d^5 \, 4s^2$$

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.

Conclusion: Both Statement I and Statement II are true. Therefore, the correct option is A.

Given: The comparison is based on successive ionization enthalpies of transition elements Cr and Mn.

Find: Use electronic configuration stability to judge both statements.

A half-filled subshell has extra stability. Chromium has configuration

$$[Ar] \, 3d^5 \, 4s^1$$

while manganese has configuration

$$[Ar] \, 3d^5 \, 4s^2$$

For the first ionization, chromium loses its single $4s$ electron and reaches the especially stable half-filled $3d^5$ state. That makes removal of the first electron easier for Cr than for Mn.

After this first removal, chromium becomes $\text{Cr}^+$ with stable $3d^5$ configuration. Any further electron removal disturbs this stability, so the second and third ionization enthalpies become comparatively higher.

Thus, Statement I is true and Statement II is true, so the correct option is A.