Question

Draw the atomic orbital for the complex
[FeF6]^ 3 -

Answer 1

I will touch by bit basics (assuming you have some idea on Crystal Field Theory, Ligand Field Theory and Hybridisation.)

[FeF6] 3- :Hexafluoroferrate

To explain with ease, I have taken some images from the internet.

Fe-atomic no. 26: Electronic configuration [Ar] 3d6 4s2, arranged as:



When Fe forms [FeF6] 3-, it no longer retains its pure atomic orbitals (s, p, d, f), rather, the orbitals of Fe and F mix together to form what we call Hybrid orbitals (sp3, sp3d2, etc.), which have very different shapes and energy levels from the componenet orbitals.

[FeF6] 3- is a an octahedral high-spin complex. Below is a structure resembling it, where E is the central metal ion and X is surrounding F-.



Octahedral complexes have sp3d2 hybridisation:



In case of octahedral geometry, the d orbitals of Fe split into two sets with an energy difference of Δoct:





The middle line is called the Barycentre.

Now spot the difference in splitting between these two Fe-complexes:



Note how Δoct is less for the first as compared to the second.

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