Case: Read the passage and answer the following questions
Crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually d or f orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbours). This theory has been used to describe various spectroscopies of transition metal coordination complexes, in particular optical spectra (colours). CFT successfully accounts for some magnetic properties, colours, hydration enthalpies, and spinel structures of transition metal complexes, but it does not attempt to describe bonding.
Which of the following complexes shows zero crystal field stabilization energy?
Answer & explanation
Correct answer: option 4
[Fe(H2O)6]3+
x + 6(0) = 3
x = 3
Fe electronic configuration [Ar]3d64s2
Fe3+ electronic configuration [Ar]3d5
Due to this weak ligand 5 electrons exist as t2g3 eg2
CFSE = 3 x (-0.4) + 2 x 0.6 = -1.2 + 1.2 = 0