The hybridization and magnetic behaviour of cobalt ion in $$\mathrm{[Co(NH_3)_6]^{3+}}$$ complex, respectively is :

Which of the following cannot be explained by crystal field theory?

The primary and secondary valencies of cobalt respectively in $$\mathrm{[Co(NH_3)_5Cl]Cl_2}$$ are :

Octahedral complexes of copper(II) undergo structural distortion (Jahn-Teller). Which one of the given copper (II) complexes will show the maximum structural distortion? (en - ethylenediamine; $$\mathrm{H}_{2} \mathrm{~N}_{-} \mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{NH}_{2}$$)