What is the average oxidation number of tungsten in the ion. ${\mathrm{W}}_6{\mathrm{O}}_6{\mathrm{Cl}}_{12}^{2-}$?

The average oxidation number of tungsten in the ion ${\mathrm{W}}_6{\mathrm{O}}_6{\mathrm{Cl}}_{12}^{2-}$ is,
$$\begin{gathered} =22/6 \\ =3.7 \end{gathered}$$

Oxidation number,

${\mathrm{W}}_6\to +22$

${\mathrm{O}}_6\to -12$
 ${\mathrm{Cl}}_{12}^{2-\to }-12$
Hence correct option is C.