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. `Ti^(3+)(aq)`. is purple while `Ti^(4+)(aq)`. is colourless because:

Options

A. there is not crystal field effec in `Ti^(4+)`
B. The energy difference between `t_(2g) and e_(g) Ti^(4+)` is quite high and does not fall in the visible region
C. `Ti^(4+)` has `d^(0)` configuration
D. `Ti^(4+)` is very small in comparison to `Ti^(3+)` and hence does not absorb any radiation

Answer

C