Question

Answer in brief.

With the help of the crystal field, energy-level diagram explain why the complex [Cr(en)₃]^3⊕ is coloured?

Answer 1

i. The central metal ion titanium has electronic configuration 3d³ and the electrons occupy one of the t_2g orbitals.

d - d transition in d' system

ii. The absorption of the wavelength of light promotes an electron from the t_2g level to e_g level. Therefore, in the complex [Cr(en)₃]³⁺, d-d transitions are possible. Hence, the complex is coloured.