Crystal Field Theory: A correction of VBT

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Hey pals, today we are going to read about CFT.

It is a small post on Crystal Field Theory. Hope you will find some value from here.

Statements of CFT:

  1. According to CFT central metal atom work as a cation and ligands work as an anion so they can perform crystalline structure.
  2. Those complexes in which CMA(central metal atom) utilizes their ‘d’ orbits are known as Low spin complex Inner ‘d’ complex or hyper ligated complex. { strong ligand→ inner ‘d’ complex}
  3. Those complexes which utilize outer ‘d’ orbitals are known as high spin complex Outer ‘d’ complex or hypo ligated complex. { weak ligand→ outer ‘d’ complex}
  4. When the strength of ligands on the half of their basic strength arrange in increasing order, then a series obtain there called as Spectro Chemical Series(SCS). The SCS is  C>N>O>X-.
  5. The magnetic strength of complex depends on the spin magnetic moment of unpaired e- which can be calculated by, 𝜇m =√{n(n+2)} B.M.
  6. When a strong ligand approach towards ‘d’ orbitals of C.M.A then ‘d’ orbital split into two different parts with greater energy difference. This energy difference is known as Crystal Field Splitting Energy(C.F.S.E) which is responsible colour behaviour of complex.

Complex colour is always in the complementary form of absorbed wavelength(𝜆).

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∴Strong Ligand∝C.F.S.E{energy gap(Δ)}∝1/𝜆

The Drawbacks of Crystal Field Theory:

The Crystal Field Theory is undoubtedly very useful and significant as compared to V.B.T. But this theory has also some drawbacks.
  1. This theory only works on d-orbitals of a central atom. The s and p orbitals are not considered.
  2. In this theory, it is said that the interaction between metal ligand is purely electrostatic which is not purely true.
  3. C.F.T fails to explain the behaviour of certain metals which cause large splitting while others show small splitting. For example, the theory has no explanation as to why H2O is a stronger ligand as compared to OH.

So, these are some drawbacks of Crystal Field Theory.

For more information, you can visit Co-ordination Compound.

If you have any queries or I’ve missed anything then pls comment to us. Thank you.

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Snehasish Konger
Snehasish Konger

Snehasish Konger is the founder of Scientyfic World. Besides that, he is doing blogging for the past 4 years and has written 400+ blogs on several platforms. He is also a front-end developer and a sketch artist.

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