In general, ligands can be arranged in a series in the order of increasing
field strength as given below:
I
– < Br
– < SCN
– < Cl
– < S
2– < F
– < OH
– < C2O4
2– < H2O < NCS
–
< edta
4– < NH3 < en < CN
– < CO
Such a series is termed as spectrochemical series It is an
experimentally determined series based on the absorption of light
by complexes with different ligands Let us assign electrons in the d
orbitals of metal ion in octahedral coordination entities Obviously,
dthe single d electron occupies one of the lower energy t2g orbitals