Which of the following statements about the Valence Bond Theory (VBT) is incorrect?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → It distinguishes between weak and strong ligands.
Valence bond theory explains the formation, structures and magnetic behaviour of many complexes through hybridised orbitals of the metal ion, but it has a set of known shortcomings.
One of them is that it does not distinguish between weak and strong ligands; that difference comes from crystal field theory, through the size of the d orbital splitting.
Option (1) It does not explain the colour exhibited by coordination compounds. — Correct about VBT. VBT has no idea of d orbital splitting, so it cannot account for d–d transitions and colour.
Option (2) It does not make exact predictions regarding the tetrahedral and square planar structures of 4-coordinate complexes. — Correct about VBT. It cannot tell in advance whether a 4-coordinate complex uses sp3 or dsp2 orbitals; the shape is decided only after the magnetic data are known.
Option (3) It does not give a quantitative interpretation of the kinetic stabilities of coordination compounds. — Correct about VBT. VBT is a qualitative picture and gives no numbers for the stability of complexes.
Option (4) It distinguishes between weak and strong ligands. — Incorrect about VBT. This is the reverse of one of its listed limitations: VBT does not tell weak field ligands from strong field ones.
NCERT (2026-27 edition):
5.5.3 Limitations of Valence Bond Theory – “While the VB theory, to a larger extent, explains the formation, structures and magnetic behaviour of coordination compounds, it suffers from the following shortcomings: …
(vi) It does not distinguish between weak and strong ligands.”