Crystal field theory (CFT)

How does CFT differ from VBT ?

What are the limitations of VBT as compared to CFT ?

Write down the merits of crystal field theory over VBT ?

Compare crystal field theory and VBT ?

Why crystal field theory is preffered over VBT ?

 The crystal field theory does not consider the _____ character in metal-ligand bonding.

Write any two limitation of crystal field theory.

Draw a figure of splitting of $\mathrm{d}$-orbital in square planner complexes.

Define the crystal field splitting in square planner complexes.

 An octahedral complex $\text{'}\mathrm{X}\text{'}$ with magnetic moment $3.87 \mathrm{BM}$ may have:

(a) ${\mathrm{d}}^3$ configuration with weak field ligand.

(b) ${\mathrm{d}}^3$ configuration with strong field ligand.

(c) ${\mathrm{d}}^6$ configuration with strong field ligand.

(d) ${\mathrm{d}}^7$ configuration with weak field ligand.

Crystal field splitting energies for octahedral $\left({\mathrm{\Delta }}_0\right)$ and tetrahedral $\left({\mathrm{\Delta }}_{\mathrm{t}}\right)$ geometries caused by the same ligands are related through the expression

The order of octahedral crystal field energy for $\text{'}{\mathrm{e}}_{\mathrm{g}}\text{'}$ orbitals are

For next two question please follow the same

When degenerate $\mathrm{d}$-orbitals of an isolated atom/ion come under influence of magnetic field of ligands, the degeneracy is lost. The two set t_2g (d_xy, d_yz,d_xz) and e_g (d_z², d_x²-y²) are either stabilized or destabilized depending upon the nature of magnetic field. It can be expressed diagrammatically as :



Value of $\mathrm{CFSE}$ depends upon nature of ligand and a spectrochemical  series has been made experimentally, for tetrahedral complexes, $\mathrm{\Delta }$ is about $4/9$  times to ${\Delta }_0$ ($\mathrm{CFSE}$ for octahedral complex). This energy lies in visible region and i.e., why electronic transition are responsible for colour. Such transitions are not possible with ${\mathrm{d}}^0$ and ${\mathrm{d}}^{10}$ configuration.

${\mathrm{Cr}}^{3+}$ form four complexes with four different ligands which are [Cr(Cl)₆]^3-, [Cr(H₂O)₆]³⁺, [Cr(NH₃)₆]³⁺ and [Cr(CN)₆]^3-. The order of $\mathrm{CFSE}$ $\left({\Delta }_0\right)$ in these complexes is in the order :

Explain in detail the limitation of Crystal Field theory.

State any two limitations of Crystal Field Theory.

Increasing crystal field strength of the different ligands is :

What are weak field and strong field ligands? What is spectrochemical series?

In an octahedral crystal field, draw the figure to show splitting of $\mathrm{d}$-orbitals.

Explain the octahedral geometry of complexes.