Clathrates are defined as ......

Percentage of $Ar$ in air is about (in $\%$)

The noble gas element that forms the largest number of compounds is .......

At $143 \ K$,the reaction of $XeF_4$ with $O_2F_2$ produces a xenon compound $Y$. The total number of lone pair$(s)$ of electrons present on the whole molecule of $Y$ is . . . . .

$XeF_6$ dissolves in anhydrous $HF$ to give a good conducting solution which contains:

$Xe_{(g)} + 3F_{2(g)} \xrightarrow{573 \ K, 60-70 \ bar} XeF_{6(s)}$ ($1:20$ molar ratio).
$XeF_6 + H_2O \rightarrow XeOF_4 + 2HF$ $(Y)$
$XeF_6 + 3H_2O \rightarrow XeO_3 + 6HF$ $(Z)$
The correct statements regarding $Y$ and $Z$ are:
$I$. $Y$ has square pyramidal geometry
$II$. $Y$ has linear geometry
$III$. $Z$ has $3 \sigma, 3 \pi$ bonds and $1$ lone pair of electrons on the central atom
$IV$. $Z$ has tetrahedral geometry