the oxidising power of oxoanions are in the order VO2+ <Cr2O72-<MnO4- explain how

 We are given an oxocation (VO₂ ⁺) and two oxoanions (Cr₂O₇ ^2- and MnO₄ ^-) of the transition metals. The ions in which the central metal atom is present in the highest oxidation state will have the highest oxidising power. In VO₂ ⁺, vanadium is present in the +5 oxidation state, while in Cr₂O₇ ^2- ion, Cr is present in the +6 oxidation state. Similarly in the MnO₄ ^-, Mn is present in the +7 oxidation state. Thus as the oxidation state of the central metal atom increases in the order

 V < Cr < Mn

therefore the oxidising power of the oxo ions increases in the order

 VO₂ ⁺ < Cr₂O₇ ^2- < MnO₄ ^-