For the octahedral complexes of F e 3 + in S C N - (thiocyanato -S) and in C N - ligand environments, the difference between the spin-only magnetic moments in Bohr magnetons (when approximated to the nearest integer) is [Atomic number of Fe = 26]

Step-by-step solution

As S C N - and C N - are weak and strong ligands respectively so during complex formation their behaviours are different. S C N - being a weak ligand can not pair inner 3d electrons so F e 3 + i.e. A r 18 3 d 5 For weak ligand, t 2 g 3 e g 2 , i.e. n = 5 As C N - being a strong ligand can pair inner 3d electrons so For strong ligand, t 2 g 5 e g 0 , i.e. n = 1 Magnetic moment = n ( n + 2 ) B . M . = 5 ( 5 + 2 ) = 35 B . M . for weak ligand. Magnetic moment for strong ligand = 1 ( 1 + 2 ) = 3 B . M . Difference in m