JEE Main · 2023 · 08 Apr 2023 · Shift 2 · d and f Block Elements

In iron pentacarbonyl the carbonyl ligands are neutral, so iron is in the zero oxidation state. In the vanadyl ion the oxygen contributes $-2$ and the overall charge is $+2$, so vanadium is $+4$. In tungsten trioxide the three oxygens contribute $-6$ to a neutral molecule, so tungsten is $+6$. The sum of the oxidation states is $0+4+6=10$.