When degenerate d-orbitals of an isolated atom/ion come under influence of magnetic field of ligands, the degeneray is lost. The two set `t_(2g)(d_(xy),d_(yz),d_(xz)) and e_(g) (d_(x^(2))-d_(x^(2)-y^(2))` are either stabilized or destabilized depending upon the nature of magnetic field. it can be expressed diagrammatically as:

Value of CFSE depends upon nature of ligand and a spectrochemical series has been made experimentally, for tetrahedral complexes, `Delta` is about 4/9 times to `Delta_(0)` (CFSE for octahedral complex). this energy lies in visible region and i.e., why electronic transition are responsible for colour. such transition are not possible with `d^(0) and d^(10)` configuration.
Q. The vlaue of CFSE `(Delta_(0))` for completes given below follow the order,
(I) `[Co(NH_(3))_(6)]^(3+)`
(II) `[Rh(NH_(3))_(6)]^(3+)`
(III) `[IR(NH_(3))_(6)]^(3+)`

Options

A. `I lt II lt III`
B. `I gt II gt III`
C. `I lt II gt III`
D. `I=II=III`

Answer

A