Question

Which of the following statements are correct?
(I) Valence bond theory cannot explain the colour exhibited by transition metal complexes.
(II) Valence bond theory can predict quantitatively the magnetic properties of transition metal complexes.
(III) Valence bond theory cannot distinguish ligands as weak and strong field ones.

• A. (I) and (III) only
• B. (I) and (II) only
• C. (I), (II) and (III)
• D. (II) and (III) only

Answer 1

The correct option is A (I) and (III) only

(I) The colour of the complexes depends on the electronic transition made by the electrons in d-orbital. VBT can't predict any such electronic transition. Hence this is right.
(II) VBT can only predict whether there are unpaired or paired electrons which denotes if they are paramagnetic or diamagnetic. This only gives a qualitative property and not quantitative property.
VBT can't predict magnetic properties of transition element. Hence this is wrong.
(III) Weak field and strong field ligands are determined by spectral transition and VBT can't predict that. Hence this is right.