How many unpaired electrons would you expect for the complex ion: [FeCl₆]^4-? A) 2 B) 6 C) 4 D) 3 E) 0

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Quizplus · Accepted Answer

The complex ion [FeCl₆]^4- has Fe as the central atom which has 6 valence electrons. Cl is a weak field ligand and hence, it produces a high-spin complex. So, in this complex, all 6 electrons pair up with their respective partner electrons from chloride ions. Both sulfur ions (₆) act as strong field ligands and split the d-orbitals of Fe into two sets, namely t2g and eg. ^4- ions donate one electron each to the two sets of orbitals. One electron from each set remains unpaired in the eg orbitals. Therefore, the number of unpaired electrons is 2+2=4.

How Many Unpaired Electrons Would You Expect for the Complex