Consider the following octahedral complexes: [ Co ( NH ₃)₆]³⁺ , [ CoF ₆]³⁻ , [ Fe ( CN )₆]⁴⁻ , [ Ni ( NH ₃)₆]²⁺ , [ Cr ( H ₂ O )₆]³⁺ The total sum of unpaired electrons present strictly in the outer-orbital complexes among the given species is

Step-by-step solution

To find the outer-orbital complexes, we apply Valence Bond Theory (VBT): 1. [ Co ( NH ₃)₆]³⁺ : Co ³⁺ is 3d^6 . NH ₃ acts as a strong field ligand for Co ³⁺ , causing pairing of electrons. The hybridization is d^2sp^3 (inner orbital). 2. [ CoF ₆]³⁻ : Co ³⁺ is 3d^6 . F ^- is a weak field ligand, so no pairing occurs against Hund's rule. The hybridization is sp^3d^2 (outer orbital). The configuration is t_ 2g ^4 e_g^2 , giving number of unpaired electrons, n = 4 . 3. [ Fe ( CN )₆]⁴⁻ : Fe ²⁺ is 3d^6 . CN ^- is a strong