$A$ black coloured element with $ns^2 np^1$ outer electronic configuration cannot react with air in its crystalline form. However, in amorphous form, it gives an oxide in air which is acidic in nature. Identify the element.

Hydrolysis of $BCl_3$ gives $X$,which on treatment with sodium carbonate produces $Y$. $X$ and $Y$,respectively,are

In which of the following reactions is hydrogen one of the products?
$i$. $2NaBH_4 + I_2 \longrightarrow$
$ii$. $2BF_3 + 6NaH \xrightarrow{450 \ K}$
$iii$. $4BF_3 + 3LiAlH_4 \longrightarrow$
$iv$. $3B_2H_6 + 6NH_3 \xrightarrow{\text{heat}} 2B_3N_3H_6 + 12H_2$

$A$ Lewis acid '$X$' reacts with $LiAlH_4$ in ether medium to give a highly toxic gas,'$Y$'. '$Y$' when heated with $NH_3$ gives a compound known as inorganic benzene. '$Y$' burns in oxygen and gives $H_2O$ and '$Z$'. '$Z$' is

When borax is dissolved in water, the product formed is

Match the following:

List-$I$ (Group $13$ element)	List-$II$ (Metallic radius,$pm$)
$A$. $Al$	$I$. $135$
$B$. $Ga$	$II$. $143$
$C$. $In$	$III$. $170$
$D$. $Tl$	$IV$. $167$

The correct answer is: