Find the non-semiconductor element among the following.

$X \xrightarrow{CoCl_2} CaCl_2 + Y \uparrow$; the effective ingredient of $X$ is

Observe the following reactions (unbalanced):
$P_2O_3 + H_2O \rightarrow X$
$P_4O_{10} + H_2O \rightarrow Y$
The number of $P=O$ bonds present in $X$ and $Y$ are respectively:

Choose the correct statement from the following with reference to the inert pair effect.

The silicates which contain $Si_2O_7^{6-}$ units are called

$FeS_2$ is