In the form of dichromate, Cr(VI) is a strong oxidising agent in acidic medium but Mo (VI) in $MoO_3$ and W (VI) in $WO_3$ are not. Choose the correct reason from the options given below:
(A) Cr (VI) is more stable than Mo (VI) and W (VI)
(B) Mo (VI) and W (VI) are more stable than Cr (VI)
(C) Higher oxidation states of heavier members of group-6 of transition series are more stable
(D) Lower oxidation states of heavier members of group-6 of transition series are more stable
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B) and (C) only
One of the notable features of a transition elements is the great variety of oxidation states these may show in their compounds. The variability of oxidation states, a characteristic of transition elements, arises out of incomplete filling of d orbitals in such a way that their oxidation states differ from each other by unity. Although in the p–block the lower oxidation states are favoured by the heavier members (due to inert pair effect), the opposite is true in the groups of d-block.
In d block higher oxidation states are favoured by heavier members.
In group 6, Mo(VI) and W(VI) are found to be more stable than Cr(VI). Thus Cr(VI) in the form of dichromate in acidic medium is a strong oxidising agent, whereas $MoO_3$ and $WO_3$ are not.
Statements B and C are correct