Q.With the help of crystal field energy-level diagram explain why the complex [Cr(en)3]3+ is coloured ?

Most transition-metal complexes are coloured because the ligand field splits the metal's d orbitals into t2g and eg sets (Crystal Field Theory), and white light falling on the complex excites an electron from the lower t2g level to the higher eg level -- a d-d transition -- by absorbing exactly the wavelength of visible light whose energy matches Δ₀. The colour actually SEEN is the complementary colour of the li …