CRYSTAL FIELD THEORY

 Crystal Field Theory (CFT)

This electrostatic approach towards the interaction between a metal ion and the ligand is known as crystal Field Theory (CFT)

Ligand

  Any atom ,ion, or molecule capable of donating a pair of electron to the central atom is called a ligand.

 In a ligand the specific atom which actually donates the electron pair is called the donar atom.

  Ex-:Amonia, nitrogen, Sulphur....etc

Three type of ligand

1. Unidentate Ligand (Monodentate)

     Ligand which can coordinate to the central ion donate through only one pair of electron are known as Unidentate Ligand.

Ex: NH3, NH2NH3+, H2O etc

2. Bidentate Ligand

  Ligand which have the donar atom donate the two pair of electron are called bidentate Ligand.

Ex: NH2CH2CH2NH2 etc

3. Polydentate Ligand 

Ligand having more than two donar atom present in the molecule are called polydentate Ligand.

Ex: Tetradentate, Hexadentate,  Pentadentate etc

Chelate / Chelating Ligand

   Ligand having dentivity more than one are chelating because when they combine with central metal ion they form a ring

Central ion / centre of  coordinate

 The cation to which one or more neutral molecule or anions are attached is called the Central ion 

  Central acts as acceptors. It has to accommodate electron pair donate by the donar atom of the ligand.

  Therefore it must have an empty orbitals.

Characteristics of d-orbitals

  All the d-orbitals are not same 

The orbitals dxz, dyz, dyz, are similar as four of these orbitals are aligned between the axis in definite directions.

  The four lobes of the dxz orbitals are directed along the angles of x and y axis. On the other hand four lobes of dx2-y2 orbitals are aligned in the negative and positive direction of the z-axis in addition to an angular portion lying in the x-y plane around the point of intersection of the axis.

Splitting in tetrahedral complex

Splitting in octahedral complex