Question

Explain how transition elements form coloured compounds?

Answer 1

Transitional elements:

• Transition elements are elements of Groups $3-12$ of the modern periodic table.
• Transition elements have vacant d orbitals. So, due to the presence of vacant d-orbital, they produce coloured compounds.
• Transition metal ions are not naturally coloured. They only become coloured when they form compounds with other ions or molecules.
• When visible light strikes a transition metal complex or ion, the unpaired electrons in the lower energy d-orbitals are promoted to higher energy d-orbitals, a process is known as the d-d transition.
• Since the energy involved in the d-d transition is quantized, only a specific wavelength is absorbed, while the rest of the visible spectrum is transmitted. As a result, transmitted light has a complementary colour to the absorbed colour.

Therefore, Transitional elements form coloured compounds due to the splitting of the d-orbital.