The reaction of $P_4$ with $X$ leads selectively to $P_4O_6$. The $X$ is

State the electronic configuration of group-$15$ elements.

$A$ nitrogen oxide that forms "in situ" when dilute $FeSO_4$ is treated with an aqueous solution of nitrate ion and then carefully adding conc. $H_2SO_4$ along the sides of the test tube, is

Which among the following group-$15$ elements does $NOT$ react with concentrated sulphuric acid?

Which of the following orders is correct?

$P_2O_3 + H_2O \rightarrow X$
$Red \ P_4 + \text{alkali} \rightarrow Y$
$X$ and $Y$ are oxoacids of phosphorus. The number of $P-OH$ bonds in $X$ and $Y$ respectively is: