The d & f Block Elements — Chemistry STD 12 Science — Question

Formation of coloured compounds (both in solid state as well as in aqueous solution) is another very common characteristics of transition metals. This is due to absorption of some radiation from visible light to cause d-d transition of electrons in transition metal atom. The d-orbitals do not have same energy and under the influence of ligands, the d-orbitals split into two sets of orbitals having different energies; transition of electrons can take place from one set of d orbitals to another set within the same sub shell. Such transitions are called d-d transitions. The energy difference for these d-d transitions fall in the visible region. When white light is incident on compounds of transition metals, they absorb a particular frequency and rernaining colours are emitted imparting a characteristic colour to the complex. Zn²⁺ and Ti⁴⁺ salts are white because they do not absorb any radiation in visible region.