Give reasons : (i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation state of +4. (ii) Transition metals show variable oxidation states. (iii) Actinoids show irregularities in their electronic configurations.

The magnetic moment of few transition metal ions are given below:

Write the preparation of following : (i) KMnO₄ from K₂MnO₄ (ii) Na₂CrO₄ from FeCr₂O₄ (iii) Cr₂O₇²⁻ from CrO₄²⁻