The d-And-f-Block Elements

Short Answer Type

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Explain the following facts:
Transition metals form coloured complexes.

Transition metal form coloured complexes, due to the presence of incomplete d-subshell. The electrons can be excited from one energy level to another with in the d-subshell. The energy required to cause such d-d promotions or transition falls within the visible range for all transition elements. When white light falls on an ion or compound, some of its wave lengths are absorbed due to d-d transition and others are reflected. Therefore, colour of the transition metal ion is that of the reflected light.
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