Generally transition elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured?
KMnO4 in +7 oxidation state has no d electrons but it is deep purple in colour. The colour arises due to ligand to metal charge transfer where the ligand O2- transfers charge to the metal centre.Ce (SO4)2 is also coloured due to charge transfer and is of intense yellow colour