Explain why Mo(VI) and W(VI) are found to be more stable than Cr(VI).

Give Explanatory answer that I can write in Board Exam.

In the p–block the lower oxidation states are stable for the heavier members, this is due to inert pair effect that is unavailability of s-electron to involve in bonding, the opposite is true in the groups of d-block. For example, in group 6, Mo(VI) and W(VI) are found to be more stable than Cr(VI) because the stability of high oxidation states increases down the group due to easier availability of both d and s electrons for ionization. This easier availability of d and s electron occurs as higher energy d and s orbital like 4d,5d,3s and 4s allow the orbital to loss electron easily and form stable higher oxidation state.