Explanation

Electronic configuration of chromium (Cr, Z = 24) is:

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

Electronic configuration of manganese (Mn, Z = 25) is:

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

In chromium, removal of the first electron occurs from the 4s orbital and leads to a stable half-filled \(3d^5\) configuration. Hence, the first ionization enthalpy of Cr is lower than that of Mn.

Therefore, Statement I is true.

After removal of one electron, Cr⁺ has configuration:

\[ \text{Cr}^+ : [Ar]\,3d^5 \]

This half-filled \(3d^5\) configuration is very stable. Removing the second and third electrons from chromium disturbs this stability, so higher energy is required.

For manganese, removal of electrons does not involve breaking a half-filled configuration to the same extent. Hence, second and third ionization enthalpies of Cr are indeed higher than those of Mn.

However, in JEE trend-based comparison, only second ionization enthalpy of Cr is higher, while the third does not strictly follow the given statement.

Thus, Statement II is false.

Hence, the correct answer is Statement I is true but Statement II is false.

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