One of the notable features of the transition element is the great variety of oxidation states it may show in its compounds. The elements which give the greatest number of oxidation states occur in or near the middle of the series. Manganese, for example exhibits all the oxidation states from +2 to +7. The lesser number of oxidation states at the extreme ends is either due to the loss or sharing of a few electrons (Sc, Ti) or too many d electrons of higher valence. Early in the first series scandium (II) is virtually unknown and titanium (IV) which is more stable than Ti (III) or Ti (II). On the other end, the only oxidation state of zinc is +2.

For balancing the given reaction, value of \(x\) will be:

\(4FeCr_2O_4 + xNa_2CO_3 + 7O_2 \longrightarrow xNa_2CrO_4 + 2Fe_2O_3 + 8CO_2\)

8

The correct answer is (3) 8.

The given equation is

\[4FeCr_2O_4 + xNa_2CO_3 + 7O_2 \longrightarrow xNa_2CrO_4 + 2Fe_2O_3 + 8CO_2\]

After balancing the equation, we have:

\[4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \longrightarrow 8Na_2CrO_4 + 2Fe_2O_3 + 8CO_2\]

So, the correct answer is \(x = 8\), and it corresponds to option 3.