Question

The transition metal having highest \(3^\text{rd}\) ionisation enthalpy is:

• A. Cr
• B. Mn
• C. V
• D. Fe

Answer 1

The Correct Option is B

To identify the transition metal with the highest third ionization enthalpy, analyze the electronic configurations and the stability of ions after electron removal.

The electronic configurations are:

• Chromium (Cr): \(\left[ \text{Ar} \right] 3d^5 4s^1\)
• Manganese (Mn): \(\left[ \text{Ar} \right] 3d^5 4s^2\)
• Vanadium (V): \(\left[ \text{Ar} \right] 3d^3 4s^2\)
• Iron (Fe): \(\left[ \text{Ar} \right] 3d^6 4s^2\)

The third ionization enthalpy measures the energy needed to eject the third electron. Stability, particularly that of half-filled d-orbitals, is a key factor.

For manganese (Mn), removing two electrons yields a stable \(3d^5\) half-filled d-orbital configuration.

This exceptional stability means removing a third electron from manganese requires more energy compared to the other elements listed.

Consequently, the element exhibiting the highest third ionization enthalpy is: Mn (Manganese).