GUJCET 2025 Chemistry Paper

Concept:Ligand field strength decides whether a complex is inner orbital or outer orbital.Explanation:In $\mathrm{Ni}^{2+}$, the electronic configuration is $3d^8$.In $\mathrm{[NiCl_4]^{2-}}$, $\mathrm{Cl}^-$ is a weak field ligand.It does not pair the $3d$ electrons.So hybridisation is $sp^3$, using outer $4s$ and $4p$ orbitals.Thus, $\mathrm{[NiCl_4]^{2-}}$ is an outer orbital complex.In $\mathrm{[Ni(CN)_4]^{2-}}$, $\mathrm{CN}^-$ is a strong field ligand.It pairs the $3d$ electrons and leaves one $3d$ orbital vacant.So hybridisation is $dsp^2$, using inner $3d$, $4s$, and $4p$ orbitals.Thus, $\mathrm{[Ni(CN)_4]^{2-}}$ is an inner orbital complex.Answer:Option B is correct: $\mathrm{[NiCl_4]^{2-}}$ is an outer orbital complex, while $\mathrm{[Ni(CN)_4]^{2-}}$ is an inner orbital complex.