Question

Statement I : An electron in \( e_g \) causes destabilization of \(0.6\,\Delta_o\) and an electron in \( t_{2g} \) causes stabilization of \(0.4\,\Delta_o\) as per CFT.
Statement II : All d-orbitals of transition elements are degenerate in absence of ligands but splitting occurs in presence of ligands.

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

Answer 1

The Correct Option is A

Concept:
According to Crystal Field Theory (CFT), when ligands approach a central metal ion, the degeneracy of d-orbitals is removed due to electrostatic interactions. In an octahedral field, the five d-orbitals split into two sets: \[ t_{2g} \; (d_{xy}, d_{yz}, d_{xz}) \quad \text{and} \quad e_g \; (d_{x^2-y^2}, d_{z^2}) \] The \(t_{2g}\) orbitals experience less repulsion (stabilized), while \(e_g\) orbitals face more repulsion (destabilized). \includegraphics[width=0.5\linewidth]{12c ans.png} Step 1: Evaluate Statement I. In an octahedral crystal field: \[ \text{Each electron in } t_{2g} \text{ orbitals contributes } -0.4\,\Delta_o \] \[ \text{Each electron in } e_g \text{ orbitals contributes } +0.6\,\Delta_o \] Thus, Statement I correctly describes stabilization and destabilization energies. Step 2: Evaluate Statement II. In the absence of ligands: \[ \text{All five d-orbitals are degenerate (same energy)} \] When ligands approach: \[ \text{Electrostatic interaction causes splitting of d-orbitals} \] Thus, Statement II is also correct. Step 3: Conclusion. \[ \boxed{\text{Both Statement I and Statement II are correct}} \]