Which of the following is not a limitation of valence bond theory (VBT)?

It does not explain the concept of the high spin and low spin complex.

The correct answer is Option (3) → It does not explain the concept of the high spin and low spin complex.

Core Concept

Valence Bond Theory is able to explain high spin and low spin complexes based on whether electron pairing occurs before hybridisation.

However, it fails in areas like ligand strength, colour and geometry prediction.

Detailed Option-wise Explanation

Option 1:

VBT does not differentiate between strong field and weak field ligands. This distinction is explained only by Crystal Field Theory.

Option 2:

VBT cannot explain colour in coordination compounds because it does not consider d–d electronic transitions.

Option 3:

VBT explains the formation of high spin and low spin complexes by considering whether electrons pair before hybridisation (inner orbital vs outer orbital complexes). Therefore, this is not a limitation.

Option 4:

VBT cannot predict whether a coordination number 4 complex will be tetrahedral or square planar. It assumes geometry rather than predicting it.

Therefore, the correct answer is Option 3.