Final answer:
The [Fe(CN)6]3- ion is a low-spin complex with one unpaired electron due to the strong field produced by the cyanide ligands, which leads to a significant splitting of d-orbitals and greater electron pairing.
Step-by-step explanation:
The question regards the number of unpaired electrons in the [Fe(CN)6]3- complex ion. This ion is formed when iron (Fe) bonds with six cyanide ligands (CN), which are known for creating a strong field that significantly splits the energies of the d-orbitals in the iron atom. According to crystal field theory, a strong field causes the iron electrons to pair up rather than occupy higher energy orbitals. The [Fe(CN)6]3- ion is known to be a low-spin complex, which leads to a greater degree of electron pairing and consequently fewer unpaired electrons. Specifically, the [Fe(CN)6]3- ion has one unpaired electron, in contrast to high-spin complexes like [Fe(H2O)6]3+ and [FeF6]3-, which have five unpaired electrons.