Question

Write Valence Bond Theory (VBT) of coordination compounds. Also state the demerits of this theory.

Hint:

VBT is useful for explaining the geometry of complexes but is limited in predicting their optical and magnetic properties.

Answer 1

Valence Bond Theory (VBT):
- VBT explains the bonding in coordination compounds by considering the hybridization of orbitals on the central metal atom or ion.
- The metal ion provides vacant orbitals to accommodate the lone pairs of electrons donated by ligands, forming coordinate covalent bonds.
- The geometry of the complex depends on the type of hybridization:
- \( sp^3 \): Tetrahedral
- \( dsp^2 \): Square planar
- \( d^2sp^3 \): Octahedral 

Demerits of VBT:
1. Fails to explain the color of coordination compounds.
2. Cannot account for the magnetic properties of some complexes.
3. Does not provide a quantitative measure of bond strength or stability.