Laughing gas is prepared by heating

Name three oxoacids of nitrogen. Write the disproportionation reaction of that oxoacid of nitrogen in which nitrogen is in $(+3)$ oxidation state.

The products of hydrolysis of isohypophosphoric acid are the same as those of which of the following compounds?

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

Which of the following statements is true for $PH_3$?

The element that forms stable compounds in low oxidation state is