The element that forms stable compounds in low oxidation state is

The basicity of $H_3PO_2, H_3PO_3, H_3PO_4$ respectively is

Which of the following substances are soluble in concentrated $HNO_3$?

Among the oxides of nitrogen $N_2O_3$,$N_2O_4$,and $N_2O_5$,the molecule$(s)$ having nitrogen-nitrogen bond is/are

The atomic number of $N$ is $7$. The atomic number of the $3$rd member of the nitrogen family is:

Rationalize the given statements and provide chemical reactions:
$1$. Lead $(II)$ chloride reacts with $Cl_2$ to give $PbCl_4$.
$2$. Lead $(IV)$ chloride is highly unstable towards heat.
$3$. Lead is known not to form an iodide,$PbI_4$.