Question

(i) Draw the diagram which indicates the splitting of d-orbitals in tetrahedral field. 
(ii) Write any one limitation of valence bond theory.

• A.
• B.
• C.
• D.

Hint:

Key Points:

Tetrahedral splitting: e (lower energy) and t₂ (higher energy).
In tetrahedral complexes: Δ_t < Δ_o.
Valence Bond Theory (VBT) explains geometry and magnetic properties but fails to explain the colour and electronic spectra of coordination compounds.

Answer 1

The Correct Option is A

Concept:
According to Crystal Field Theory (CFT), when ligands approach a metal ion, the degeneracy of the d-orbitals is removed due to electrostatic interactions between ligands and the d-electrons. In a tetrahedral complex, ligands approach between the coordinate axes, resulting in a specific pattern of orbital splitting.

Step 1: Splitting of d-orbitals in Tetrahedral Field.
In a tetrahedral field, the orbitals pointing between the axes experience greater repulsion and therefore have higher energy.

Higher energy: t2 (dxy, dyz, dzx)
Energy gap: Δt
Lower energy: e (dx2−y2, dz2)

The t2 orbitals (dxy, dyz, dzx) experience greater repulsion and are raised in energy.
The e orbitals (dx2−y2, dz2) experience less repulsion and remain at lower energy.

Thus, the splitting results in a higher energy t2 set and a lower energy e set.

Step 2: Limitation of Valence Bond Theory (VBT).
Valence Bond Theory explains the geometry and magnetic properties of coordination compounds but has certain limitations.

One important limitation is:
It cannot explain the colour of coordination compounds.

This limitation arises because VBT does not account for the splitting of d-orbitals and electronic transitions responsible for colour.