Crystal Field Theory

$\text{Statement I}$ :  [Ti(H₂O)₆]⁴⁺ is coloured while [Sc(H₂O)₆]³⁺ is colourless.
$\text{Statement II}$ : d - d transition is not possible in [Sc(H₂O)₆]³⁺

The correct order for the wavelengths of absorption in the visible region for the following is: ${\left[\text{Ni}{\left({\text{NO}}_{\text{2}}\right)}_6\right]}^{4-},{\left[\text{Ni}{\left({\text{NH}}_{\text{3}}\right)}_6\right]}^{2+},{\left[\text{Ni}{\left({\text{H}}_{\text{2}}\text{O}\right)}_6\right]}^{2+}$

Define weak field ligands.

Define strong field ligands.

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

Write any two limitation of crystal field theory.

Which of the following compounds is not coloured?

 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

According to crystal field theory, total number of unpaired electrons present in the following molecules ${\left[{\mathrm{NiCl}}_4\right]}^{2-}, {\left[\mathrm{Ni}(\mathrm{CN}{)}_4\right]}^{2-}$ and ${\left[\mathrm{Ni}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ will be

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 :

Blue coloured copper sulphate solution gave following experimental results. Explain the same. With aqueous potassium fluoride it gave a green precipitate.

Blue coloured copper sulphate solution gave following experimental results. Explain the same. With aqueous potassium chloride it gave bright green solution.

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.