Which of the following are true for the Crystal Field Model ofan octahedral comp

Question

Which of the following are true for the Crystal Field Model ofan octahedral complex ion? Consider ions to be from first-rowtransition metals.

a) The ligands cause a splitting of energy of the 3dorbitals

b) eg orbitals are more stable than t2orbitals

c) A small crystal field splitting energy results in aparamagnetic complex

d) The low--spin case gives minimum unpaired electrons

e) For a given ligand, Fe3+ increases splitting lessthan Fe2+
think about the amount of coulombic attraction between the metalion and the electrons on the ligands
and the closer the ligands, the more interaction there is with thed orbitals on the metal ion

f) Cl- causes a greater increase inthe crystal field splitting enery than does H2O

g) The splitting of energy (E) of 3d orbitals occurs in theligands

Explanation / Answer

         According toCrystal field theory the interaction between the ligands andthe metal ion is purely electrostatic. When the ligands approachthe metal ion the d orbitols lost their degeneracy dueto the repulsion between the electrons of  the ligandsand the d electrons of the metal ion . So the ligandscause the splitting of the d orbitlols .    The spitting of the d orbitols depends on thearrangement of ligands around the metal ion. For octahedralgeometry eg orbitols are more stable than the t2g orbitols . For the tetrahedral geometry t2 orbitols are more stablethan the e orbitols.     If the crystal field splitting parametre() is greater than the pairing energy then the electronsgets paired in the orbitols instead of filling in the egorbitols .So the low spin complexes gives the minimum unpairedelectrons which cause larger splitting . If the crystal fieldsplitting paramere is lower than the pairing energy ( weak fieldligands) then there is no pairing . So the paramagnetic complexformed.    The magnitude of the crystal field splittingparametre depends on the oxidation state of the metal ion . Higher the oxidation  state of the metal ion greater theinteraction with the ligands so larger will be the splitting.    Cl- is weak ligand thanH2O so it cause small crystal field splittingthan H2O .     The splitting of energy of the 3d orbitolsoccurs in the metal ion.      The true statements are a) ,c) and d)

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