Write the representation of sodium hexacyanoferrate (III)(b) Write type of hybridization and magnetic behaviour of the following –(i) [Co(NH3)6]3+(ii) [NiCl4]2–

Answer:

(a) Na₃[Fe(CN)₆] (Fe is +3; charge on complex = 3 – 6 = –3, balanced by 3Na⁺).

(b) (i) [Co(NH₃)₆]³⁺: Co³⁺ is 3d⁶. NH₃ is a strong field ligand here, so the six d electrons pair up in three 3d orbitals, leaving two 3d orbitals empty. These two 3d, one 4s and three 4p orbitals give d²sp³ hybridisation (octahedral, inner orbital complex). No unpaired electrons, so it is diamagnetic.

(ii) [NiCl₄]^2–: Ni²⁺ is 3d⁸. Cl^– is a weak field ligand, so no pairing occurs; the 3d orbitals keep two unpaired electrons. One 4s and three 4p orbitals hybridise: sp³ (tetrahedral). With 2 unpaired electrons it is paramagnetic (μ ≈ 2.83 BM).